Gastrointestinal absorption remains indispensable in the systemic delivery of most drugs, even though it presents several challenges that, paradoxically, may also provide opportunities that can be exploited to achieve maximal bioavailability. Drug delivery systems made from nanoparticle carriers and especially, lipid carriers, have the potential to traverse gastrointestinal barriers and deploy in the lymphatic pathway, which aptly, is free from first pass via the liver. Several poorly soluble drugs have presented improved systemic bioavailability when couriered in lipid nanoparticle carriers. In this review, we propose an additional frontier to enhancing the bioavailability of poorly soluble drugs when encapsulated in lipid nano-carriers by imparting muco-adhesion to the particles through application of appropriate polymeric coating to the lipid carrier. The combined effect of gastrointestinal muco-adhesion followed by lymphatic absorption is a promising approach to improving systemic bioavailability of poorly soluble drugs following oral administration. Evidence to the potential of this approach is backed-up by recent studies within the review. For example, idarubicin-loaded SLNs showed a 21-fold increase in systemic bioavailability following oral administration, reflected through the area under the curve (AUC) and a 30-fold extended elimination half-life as compared to idarubicin solution . In anotl/Neoral ,77.Despite these advantages, SLNs suffer from low API loading capacity with significant drug expulsion during storage, due to the polymorphic transformation of the lipids ,30,53. TNLCs formulations were developed in 2000 and within five years, two NLCs products were approved to be marketed  ,79. NLC In contrast to the SLNs, NLCs formulations comprise of a blend of solid lipid with liquid oil . DespiteNLCs can be categorised as imperfect, amorphous or multiple NLCs according to the structure of the lipid matrix ,84. In iSeveral highly lipophilic drugs have been encapsulated within NLCs for systemic bioavailability enhancement, most belonging to the BCS Class II, such as vinpocetine , lovastaSufficient GI uptake of the lipid nanoparticle along with its API cargo is the first and crucial step toward the systemic delivery of the API. However, it is important to recognize other potential barriers within the GI tract as well. For example, the mucosal layer as mentioned earlier, which serves as a protective layer to the underlying epithelia, presents a frontier that particulate delivery system must traverse. Fortunately, lipid nanoparticles have some tendency to adhere onto the mucosal layer and therefore able to oppose dislodging imposed by propulsive forces from GI motility ,45. SuchIn a cell culture study on the permeability of NLCs across Caco-2 and HT-29 MTX co-culture, significant variation was observed between type of cell, where lower NLCs uptake occurred in cells without mucus (Caco-2) compared to HT-29 MTX, which expresses the mucosal layer .Furthermore, charged particles may adhere electrostatically or be repelled from the mucosal layer depending on the resident surface charge on the particles, noting that, mucin is negatively charged due to sialic acid groups ,100. AltUpon oral ingestion, part of the lipid nanoparticles may become degraded or digested by gastric lipase aided by shear forces  in the stomach, which forms a crude emulsion ,103. In Furthermore, the colloidal structures or some intact lipid nanoparticles can either be taken up through membranous epithelial cells (M-cells) or gut enterocytes ,104. M-cThe uptake of lipid nanoparticles into gut enterocytes is mainly through the transcellular active transport of endocytosis ,106,109.Pinocytosis is more complex and may include clathrin-mediated endocytosis (CME), caveolae-mediated endocytosis (CvME), macropinocytosis, clathrin or caveolae-independent endocytosis. CME occurs in clathrin-enriched membrane and includes receptor-ligand interactions ,112. CMECvME involves cholesterol-rich or sphingolipids membranes that are lined with caveolin, a dimeric protein with a flask-shape membrane invaginations characteristic ,113. CavSimilar to phagocytosis, macropinocytosis involves protrusion and fusion of the membrane, encapsulating the particles and forms vesicles of about 1 µm. However, the process of macropinocytosis is non-selective and highly dependent on the difference in the solute concentration ,111.Lipid nanoparticles can also traverse the paracellular route after transient disruption of tight junctions between adjacent epithelial cells by permeation enhancers ,84,105. After the formed micelles are taken up by the enterocytes cells, they become converted into chylomicrons upon re-esterification via monoacyl glycerol or phosphatidic acid pathway and subsequently, stabilised by phospholipids ,76,118. The lymphatic system is an additional pathway for the absorption of lipid nanoparticles or other lipophilic compounds , in contrast to most orally administered drugs, which are transported mostly via the portal blood vein before reaching the systemic circulation ,120. TheLipid nanoparticles that are absorbed by the intestinal lymphatics are transported through the mesenteric lymph duct that enter into the thoracic duct and empty in the systemic circulation via left jugular and subclavian veins ,122. The®) dissolved in oleic acid has been exploited for lymphatic absorption which accounted for 91.5% of the total bioavailability [max compared to pure vincopecetine solution. The lymphatic pathway was hypothesised to be the main transportation route for the NLCs as opposed to the solution, which suffered significant first pass [Lymphatic absorption of lipid nanoparticles has been extensively explored as a viable means for delivering poorly soluble APIs. A commercial formulation of testosterone  electronic, (ii) wetting, (iii) adsorption, (iv) diffusion and (v) mechanical. The electronic phenomenon is based on the establishment of attractive forces through the transfer of electrons , forming an electrical double layer ,127,129.Taking advantage of the lymphatic pathway, lipid-based delivery systems, and especially submicron carriers, provide an avenue for the deployment of payloads via the lymphatic route into the systemic circulation. Whilst this is true in in vitro and animal models, GI delivery of lipid-based systems still fall short in the clinical settings and therefore warrants attention . Oral deN, N-dioleyl-N, N-dimethylammonium chloride (DODAC) can be formulated as cationic SLN or NLC but toxicity remains a concern [® [Within the context of the present review, attendant muco-adhesion imparted by the delivery system appear to be a rational approach for achieving both localized therapeutic action and systemic delivery through uptake by enterocytes. SLN uptake via the gastrointestinal tract can be enhanced if the transit of the particles can be extended. SLN and NLCs are inherently neutral or exhibit negative charge potential due to the lipids. However, it is possible to impart positive potential to SLN or NLC from positively charged surfactants, such as cetyltrimethylammonium bromide (CTAB). Although muco-adhesivity is achievable from such particles, toxicity concerns limit the use of positively charged surfactants , especia concern . In addr concern . SLN hav concern  or the c concern . In orde concern , which i concern ,141,142. concern . The aut concern . Lou et  concern . Enhance concern . Amphotencern [® . In a rencern [® .2+ and Ca2+ and which reduces their muco-adhesion capacity [Muco-adhesion polymers can be classified as non-ionic, anionic or cationic. Non-ionic polymers  exert their muco-adhesion through a buildup of the hydrogen bonds and entanglement of the polymer chains, independent of the surrounding pH conditions. However, they were reported to be less adhesive as compared to anionic or cationic polymers ,147. Anicapacity .Cationic polymers exhibit muco-adhesion behavior through ionic interactions between polymers and the anionic sialic acid groups of the mucus ,124. AmoThe muco-adhesion properties of conventional dosage forms or materials have been preferentially measured using methods such as tensile and shear strength tests, which directly measures the time or force needed to detach the dosage form from a model membrane . These mThe following sections will focus on the different experimental approaches used to assess the muco-adhesion potential of nanoformulations, which can be classified as indirect or direct methods . Indirect methods evaluate the balance between contributing and detrimental interactions between the nanoformulation and mucins whereas direct methods evaluate muco-adhesion in vivo or using biological tissue (ex vivo).Mucin particle method is an indirect method used to assess the muco-adhesion properties of the nanoformulation. It evaluates the degree of adsorption of nanoparticles to mucin particles through the measurement in the variation of size , zeta poBesides, the interaction between mucin in solution and nanoparticles could also be assessed through turbidity concept whereby the transmittance  or absorMicrogravimetric method evaluates the amount of material adsorbed onto the mucin using a quartz crystal microbalance . The mucAFM measures the attractive and repulsive forces exerted at molecular level through the modification of the probe tip with polymer or mucin. Interaction with different samples  will result in deflection the cantilever attached to the probe and thus, the interaction forces (both attractive and repulsive) can be measured . BesidesIn the literature, several optical techniques employ changes in properties of incident light on surface immobilised mucin when nanoparticles adsorbs to the mucin. For example, ellipsometry measures the muco-adhesion (weight of nanoparticles adsorbed per area) based on the refractive index from the mucin layer. This is shown through the study by Svensson et al. (2008), utilising chitosan-modified particles and cubosomes on mucin coated surfaces . Surface plasmon resonance optical technique utilises a resonant mirror biosensor to evaluate changes in the refractive index based on evanescent waves. The association between the nanoparticles and mucin can be obtained through the mathematical model utilising the quantitative data produced .Multiple particle tracking (MPT) has been extensively used to measure the interaction between unhindered diffusive movement of nanoparticles and mucus or mucus simulating fluid. Briefly, the fluorescent nanoparticles are incubated with mucus and placed under video microscopy to obtain high resolution 2D trajectories. The muco-adhesion properties can be evaluated based on quantitative parameters such as diffusivity/immobility and transport mode of tracked nanosystems ,161.Generally, this type of study evaluates the adhesion of fluorescent labelled nanoparticles in epithelial cell monolayer using fluorescent microscopy. It is simple to execute but suffers from disadvantages such as lack of tissue architecture and functionality . Hence, The ex vivo muco-adhesion method evaluates the degree of retention of radiolabeled or fluorescent-labelled nanoparticles in mucosal tissue explants . SimplerThis method involves administration of fluorescent compounds (e.g., Cy 5.5 , sulforhThe major limitation to this method is the ethical constraints associated with the number of animals required for the experiment. Nevertheless, this technique allows good representation of the physiological washing, which is absent in the indirect and ex vivo methods as such could potentially influence the adhesion and retention of the nanoparticles .Lipid nanoparticulate carriers provides a means for deploying APIs cargoes systemically, when delivered orally, by virtue of lymphatic uptake of the particles. In this regard, the bioavailability of several class III or IV drugs have been improved when formulated as orally administered lipid nanoformulations. Further improvement in systemic bioavailability can be achieved through delayed GI transit of the particles, when the latter is coated with muco-adhesion polymers. It is the view of the authors that more of the above classes of drugs that previously were delivered by alternative routes will now be prospective candidates for oral delivery via lipid nanoformulation cum GI muco-adhesion. Furthermore, lipid polymers that possess muco-adhesion properties should be investigated as possible carrier systems. Chemical conjugation of lipid carriers to muco-ahesive polymers will be a rational approach for use in nanoformulation. Muco-adhesion of nanoparticles as semisolid dosage form will find wide applications on mucosal surfaces for the treatment of localized diseases. In regard case, gradual release of the API from the resident formulation provides an effective therapeutic supply to concerned tissue. Lipid nanoformulation presents an alternative means to delivering poorly soluble APIs to the systemic circulation following oral administration and GI absorption, noting that insignificant bioavailability results from administration of such pure APIs. This review captures evidence supporting the emergence of an additional dimension in the utilization of lipid nanoformulation in for enhancing the systemic bioavailability of the API. This can be achieved through use of suitable polymers adequately adsorbed to the lipid nanoparticle in order to impart muco-adhesivity, thus extending the GI transit times. This allows lateral incursions across the epithelia ultimately feeding into the lymph. The combined approach works better in enhancing the bioavailability of the API than either used alone. One area where this approach will find wide application is the treatment of local conditions within the GI tract whereby lipid nanocarriers deploy through muco-adhesion and gradual release of the API.


Mucopolysaccharidoses are extremely rare diseases that are frequently presenting with structural heart problems of the aortic and mitral valve in combination with myocardial dysfunction. In a substantial proportion, this leads to heart failure and is a leading cause of death in these patients. As this glycosaminoglycan degradation defect is associated with other conditions strongly influencing the perioperative risk and choice of surgical technique, multidisciplinary planning is crucial to improve short- and long-term outcomes. The extensive variance in clinical presentation between different impaired enzymes, and further within subgroups, calls for personalised treatment plans. Enzyme replacement therapies and bone marrow transplantation carry great potential as they may significantly abrogate the progress of the disease and as such reduce the clinical burden and improve life expectancy. Nevertheless, structural heart interventions may be required. We reviewed the existing literature of the less than 50 published cases regarding surgical management, technique, and choice of prostheses. Although improvement in therapy has shown promising results in protecting valvar tissue when initiated in infancy, concerns regarding stability of this effect and durability of biological prostheses remain. Mucopolysaccharidoses (MPS) describe a family of rare inherited lysosomal storage diseases characterised by specific deficiencies in lysosomal enzymes necessary for the degradation of glycosaminoglycans (GAGs). Despite cardiac involvement being common in MPS, leading to structural heart disease in 49–90% of cases , currentMPS subtypes are differentiated biochemically by associated lysosomal enzyme deficiency and resulting GAG accumulation. Currently, seven distinct types of MPS have been identified ; MPS IIIThe cumulative global incidence of MPS is estimated to be 1.04–16.9 cases per 100,000 live births . The incA broad variation of clinical presentation exists even within MPS types and subtypes . The couThe deficiency or malfunction of enzymes present in MPS are insufficient for a correct degradation of glycosaminoglycans, long linear polysaccharides with highly hydrophilic characteristics produced in the Golgi apparatus or by integral membrane synthases. This disturbance in the catabolism leads to intra-lysosomal, thus intracellular accumulation of GAG in the cardiac tissues ,24. DermProgressive cardiac valvular disease is a prominent cardiac feature of MPS and was first described in 1960 . AlthougIn valvular interstitial cells, which normally are responsible for valve growth and repair, MPS leads to activation and development of large, GAG-laden “Hurler” cells . AdditioThe intracellular accumulation of GAGs leads to formation of large Hurler cells containing clear vacuole of mucopolysaccharides which also can be found in the myocardium. The triggered inflammatory response leads to increased collagen reaction of these cells with corresponding tissue fibrosis, thus, leading to a restrictive impaired ventricular function, predominantly in the left ventricle. The resulting echocardiographic findings besides diastolic dysfunction are left ventricular hypertrophy and left ventricular remodelling . The strThe same Hurler cells can be found in large vessels. Frequent concomitant appearances are enlarged aorto-ventricular junction, valsalva and sino-tubular junction, which is found in 30–41% of patients with MPS .In addition to valvular and myocardial infiltration, deposition of GAGs can also occur in the vascular smooth muscle cells, leading to diffuse, concentric narrowing and consecutive stenosis of the coronary arteries, and additional intima hypertrophy has been described . ConsequFirst performed in patients with MPS I-H in 1981, haematopoietic stem cell transplantation (HSCT) is considered standard of care for these patients . HSCT haDespite clear improvements in life expectancy and neurosensory outcomes post-HSCT, long-term follow-up has revealed that approximately one-third of MPS I-H patients still showed progressive mitral and aortic insufficiency despite HSCT . Thus, vEnzyme replacement therapy (ERT) involves delivery of an exogenous analogue of the deficient enzyme through regular lifelong intravenous infusions. Currently approved ERTs include: laronidase (MPS I), idursulfase (MPS II), elosulfase alfa (MPS IV-A), galsufase (MPS VI), and vestronidase alfa (MPS VII) . ERT sigHowever, the efficacy of ERT in stabilising valve disease in the MPS types is not as apparent. It is postulated that the avascularity of the cardiac valves diminishes the efficacy of ERT, making it ineffectual in halting the progression of valve disease . AdditioTen-year follow-up of MPS I patients on ERT revealed that although two-thirds of patients achieved stabilisation of valve disease, approximately one-third of patients still had valvular deterioration . ProgresA variety of gene transfer and gene therapy approaches are currently in preclinical and clinical phase with 17 registered clinical trials, of which some have completed treatment with successful first safety endpoints and now progressed to a long-term follow-up phase. Further investigations on their clinical efficiency are to be expected.As a rare, complex multisystemic disease, surgery should be performed in specialist centres experienced with MPS patients. A well-planned multidisciplinary approach is necessary with experienced anaesthetic input and a joint cardiac disease multidisciplinary team meeting is recommended. The potential risks of the procedure and anaesthesia should be weighed against the benefits and extensively discussed with the patient and relatives .Other considerations include pre-operative ENT examination with naso-endoscopy or MRI assessment of the spine, brain, and airways. Additionally, coronary angiography should be performed prior to any cardiac procedure due to the increased prevalence of diffuse coronary disease in MPS patients .Respiratory symptoms are apparent across all MPS types and are important drivers of mortality . BesidesIt is important to understand that a large proportion of patients with MPS are limited in their exercise capacity due to musculoskeletal or spinal issues with a substantial number being wheelchair-bound. Therefore, it is often so that they only become symptomatic with advanced valve, myocardial or coronary artery disease. It is, therefore, important to closely monitor these patients in the cardiology clinic for subclinical advanced heart disease. MPS not only affects the heart valves, it also can lead to ventricular dysfunction with fibrosis, coronary artery disease, and electrophysiological symptoms. These three aspects of cardiac affection in MPS patients are important when planning a structural procedure, as concomitant severe coronary artery stenosis or restrictive left ventricular function will strongly influence the perioperative risk. Aortic abnormalities can also occur with MPS with a risk of dissection. Routine investigations with echocardiography and ECG should be standard of care. In situations where it is felt that the heart disease has advanced significantly so, detailed investigations are indicated. These include transthoracic echocardiography, coronary CT and CT angiography, ECG, and, if possible, cardiac magnetic resonance scanning. Coronary artery disease in these patients does not usually mimic atherosclerotic patterns, and, therefore, it is more useful to perform functional studies such as stress-echocardiography or myocardial perfusion scanning. Multidisciplinary discussions regarding consideration of intervention or surgery should always take place.Abnormal anatomical features and tissue morphology due to GAG accumulation can pose challenges regarding airway control, intubation, intravenous access, and cervical spine stability. Although surgery is frequent in MPS (MPS I 81% at least one procedure) , patientIntubation and airway difficulties are due to narrowing of the upper airways with thickening of laryngopharyngeal structures, including macroglossia, tonsillar enlargement, and narrowed nasal passages . Lower aAdditionally, cervical spine stability should be considered. Particularly in MPS IV, patients can present with odontoid hypoplasia, which is a considerable risk factor for atlantoaxial instability. If not properly managed, this can result in spinal cord compression, eventually leading to paralysis or death . TherefoCareful post-operative planning is crucial; there is an increased rate of post-operative mortality with MPS patients . IntensiThe best time point for heart valve replacement can be a challenging decision in MPS patient. Complicating factors, cardiac and non-cardiac MPS symptoms must be considered, best to be assessed in an interdisciplinary conversation considering all available medical history as well as recent cardiac and respiratory examinations. Clinical manifestation and progression show strong variation between different types of MPS, additionally individual differences between patients of the same type of the disease can be observed. Therefore, a personalised treatment plan is required for these patients.Most reported valve replacements involved mechanical rather than bioprosthetic implants. This seems an obvious choice as mechanical valves are preferable in the relatively young MPS patient population; bioprosthetic prostheses have a limited durability due to leaflet deterioration, particularly true for younger patients . AdditioAlthough current literature suggests mechanical valves as implants, under certain circumstances biological prostheses might be considered. Increasing experience in new therapy options such as ERT and optimised treatment protocols have the potential to enable prosthesis degeneration similar to that of non-MPS patients. This is particularly true for patients presenting at later stages in life, thus milder forms of MPS. For patients with neurological impairment due to MPS, or other reasons of impaired suitability for oral anticoagulation, biological implants might be considered. Furthermore, the possibility of an interventional valve-in-valve implantation has the potential to prolong the interval to reoperation in cases where a sufficiently sized valve can be used, as also mentioned by Dostalova et al. ,71. MostRegarding the effect of ERT on progress of natural valve changes, controversial experiences and considerations have been reported. During an elective aortic valve replacement, despite significant MS on echocardiography, Torre et al. elected not to perform double valve replacement on a 40-year-old MPS VI patient. The authors reasoned that, since the patient was on ERT for three years, the MS would not progress further . AdditioThe systemic nature of MPS can often cause multi-valvular incompetence. Poor annular tissue quality, often described as “friable”, “hard”, and “not pliable”, has been reported to complicate valve implantation in MPS patients ,65,74,75Regarding aortic valve replacement, one of the first MPS patients to undergo a mechanical valve replacement received a Braunwald–Cutter prosthesis and was reported to be well 19 years later, having undergone further elective aortic and mitral valve replacements ,77. SimiNick’s technique for root enlargement has been used successfully in several MPS patients , this isKonno aorto-ventriculoplasty with root enlargement has also been reported in at least one case . While tThe Ross procedure can bring the advantage of not requiring anticoagulation and expected good long-term freedom from reintervention in non-MPS patients (81% at 15 years) . Two docWhen considering the disappointing results with the Ross procedure in these patients, as well as progression of valve disease under ERT, there is scanty support for aortic valve repair, and none for complex reconstruction such as the Ozaki procedure in MPS patients.In the wider patient population, similarity in mid-term outcomes between TAVI and surgical aortic valve replacement has previously been suggested ,84. A suRegarding mitral valve replacement, the majority of cases in literature have reported challenges pertaining to small mitral annuli. Implantation of an appropriate valve size for body size may be difficult and, thus, prosthesis–patient mismatch may occur. As we know, this is associated with poor haemodynamic function, higher risk of cardiac events and increased mortality . TherefoSuccessful repair of the mitral valve in MPS patients has only been reported twice. Once in a 6-year-old MPS III patient and with very limited follow-up of one year. The repair comprised chordal shortening and a limited annuloplasty with pledget supported mattress sutures in both commissures . Albeit Surgical valve replacement is often required for the progressive, severe valvular disease that can occur in MPS patients despite advances in systemic treatment. Challenges associated with valve implantation include poor tissue quality and small valve annuli, which may necessitate annular enlargement or a small-diameter mechanical valve both for aortic and mitral position. Additionally, perioperative risks are increased in this cohort of patients, in particular due to difficulties with airway control and ventricular function. Careful multidisciplinary pre-operative planning is essential, personalised solutions for this broad spectrum of clinical presentation are necessary and procedures should be carried out by a clinical team experienced in managing MPS patients. The effect of ERT both on native valve tissue as well as bioprosthetic tissue is yet to be further investigated.


Dietary studies showed that dietary problems such as obesity are associated with other chronic diseases, including hypertension, irregular blood sugar levels, and increased risk of heart attacks. The primary cause of these problems is poor lifestyle choices and unhealthy dietary habits, which are manageable using interactive mHealth apps. However, traditional dietary monitoring systems using manual food logging suffer from imprecision, underreporting, time consumption, and low adherence. Recent dietary monitoring systems tackle these challenges by automatic assessment of dietary intake through machine learning methods. This survey discusses the best-performing methodologies that have been developed so far for automatic food recognition and volume estimation. Firstly, the paper presented the rationale of visual-based methods for food recognition. Then, the core of the study is the presentation, discussion, and evaluation of these methods based on popular food image databases. In this context, this study discusses the mobile applications that are implementing these methods for automatic food logging. Our findings indicate that around 66.7% of surveyed studies use visual features from deep neural networks for food recognition. Similarly, all surveyed studies employed a variant of convolutional neural networks (CNN) for ingredient recognition due to recent research interest. Finally, this survey ends with a discussion of potential applications of food image analysis, existing research gaps, and open issues of this research area. Learning from unlabeled image datasets in an unsupervised manner, catastrophic forgetting during continual learning, and improving model transparency using explainable AI are potential areas of interest for future studies. Despite recent advancements in medicine, the number of people affected by chronic diseases is still large . This raThe prevalence of these alarming statistics poses a serious concern. However, determining the effective remedial measures depends on different factors, ranging from a person’s genetics to their lifestyle choices. To cope with chronic weight problems, people often keep notes to track their dietary intake. In turn, dieticians require these records to estimate a patient’s nutrient consumption. However, these methods pose a challenge for users and dieticians, especially when they have to record time and estimate nutrients of diet intake . For theHowever, automatic food recognition using a smartphone camera in the real world is considered a multi-dimensional problem, and the solution effectiveness depends upon several factors. Firstly, the model can achieve optimal classification performance by training with many food images for each class. Other than that, food recognition is a complex task that involves several domain-specific challenges. There is no spatial layout information that it can exploit like, in the case of the human body, the spatial relationship between body parts. The head is always present over the trunk of the human body ,15,16 anIn addition to this, image quality from the smartphone camera is dependent on different types of cameras, lighting conditions, and orientations. As a result, the poor performance of food recognition models is highly susceptible to image distortions.Despite these challenges, many food images possess distinctive properties to distinguish one food type from another. Firstly, the visual representations of food images are of fundamental importance as it significantly impacts classification performance. Therefore, many food-recognition methods employ handcrafted features such as shape, color, texture, and location. Recent techniques are using deep visual features for image representations. Some of these methods implement a combination of handcrafted and deep visual features for image feature representations. Secondly, for enhanced classification performance and reduced computational complexity, an appropriate selection of attributes is essential for removing redundant features from feature vectors. Finally, wisely selecting classification techniques is crucial to address food recognition challenges effectively.Similarly, manual logging of food volume is a tedious task and involves a high rate of human error by as much as 30% ,20,21,22(1)The article briefly explores food databases for evaluating vision-based approaches and performance measures to thoroughly investigate food recognition, ingredient detection, and volume estimation methods.(2)It presents an extensive review of food recognition techniques, including traditional methods with handcrafted features and modern deep-learning-based approaches.(3)It provides deep insight into multi-label methods for food ingredient classification.(4)This study surveyed most performing single-view and multi-view methods for food volume estimation.(5)This study presents existing mobile applications that implement these approaches and other potential applications of vision-based methods in health care.(6)The article analyzes open issues and suggests possible solutions to overcome the limitations of the existing methodologies.The following research paper aims to scrutinize state-of-the-art vision-based approaches for dietary assessment to give researchers a summary of this area. It should be noted that the article is related to vision-based methods for food image analysis and their applications in the field of healthcare currently being discussed in the literature. However, the methodology of this article seeks to examine the systems more broadly by describing their important aspects similar to narrative overview  instead The performance of automatic food recognition models is highly dependent on the correct mapping of food images into their respective categories. Therefore, confusion-matrix and evaluation metrics play an essential role in determining the correctness of food recognition models. Several metrics have been discussed in the literature, and their appropriate selection depends on the requirements of specific applications. It has also been observed that a classifier may perform well under one metric but poorly under another metric. For example, in the context of an imbalanced food dataset, the data samples from one or more classes outnumber data samples from the remaining food classes. Then a model trained on an imbalanced data set can have higher accuracy because of its good performance on the majority classes despite having bad classification performance on minority classes. Confusion matrix and other intrinsic metrics  generally used for detailed comparisons are discussed in detail below.Confusion matrices are a widely used approach to summarize the performance of a classification model in machine learning. In some cases, classification accuracy alone can be misleading, especially when there are more than two classes in a dataset or if there were an unequal number of observations present in food classes. Therefore, the confusion matrix provides a clear picture of actual and predicted classes obtained by the classification model. The confusion matrix is basically a two-dimensional matrix where each row represents an example of an actual food class and each column represents a state of the predicted food class. TP stands for true positive, TN represents the number of true negatives, FP is the number of false positives, and FN represents false negatives in the confusion matrix shown in The accuracy of a model determines whether the model is able to predict food classes correctly or how well a certain model can generally perform. Equation  represenHere The Precision score can be defined as how often a model can correctly predict values classified as positives. In simpler words, out of all predicted positive food classes, it indicates what percentage is truly positive. This score is beneficial when the cost of false positives is high. It is calculated by Equation .(2)PrecRecall score identifies the model’s ability to correctly classify food classes. It determines out of total positive food classes what percentage is predicted positives. It provides better insight when the cost of false negatives is high. It is computed by using Equation .(3)RecaF1 score represents the harmonic mean of recall and precision score. It considers both false positives and false negatives; therefore, it performs great on imbalanced datasets. It is calculated by following Equation .(4)F1ScFood datasets are open-ended due to the large variety of food dishes and different preparation styles. There are no limitations and constraints on the number of classes, and the model can progressively adapt domain variations in existing classes while learning new food classes. However, catastrophic forgetting during progressive learning causes the neural network to forget previous knowledge while learning new concepts. Catastrophic forgetting measures compute the algorithm’s ability to retain previous concepts and knowledge while learning new information. Kemker et al.  and ChauThis refers to the difference in classification performance between the reference model trained by batch learning technique and the model trained on feature vectors using incremental learning protocol. The negative intransigence shows that incrementally learning a new set of food classes improves performance. Equation  denotes kth session.This refers to the difference between the highest classification performance of a particular session in previous sessions and its classification performance in the current sessions. Equation  computesThis refers to the model’s ability to retain the knowledge of base food classes in current sessions, as shown in Equation .(7)ΩbasThis is the ability of a model to recall newly learned food classes, as shown in Equation .(8)ΩnewThis refers to the retention of the previous food classes learned by the network when learning new food classes, as computed by Equation .(9)ΩallSimilarly, food ingredient recognition is equally important for dietary assessment applications. As food categorization is limited to the classification of generic food items present in the food images, food ingredient recognition and classification provide deep insights into the caloric content present in the food image. Therefore, food ingredient recognition applications widely incorporate multi-label classification . Since fL number of labels as training datasets. Let us assume that Consider Precision is the ratio of correctly predicted labels to the total number of actual labels, averaged across all instances. Equation  represenRecall is computed by Equation . It is tFinally, F1 score is the harmonic mean of the precision and recall. Equation  represenv is the actual volume and N is the number of food items, Similarly, various studies related to food volume estimation use ground truth values to compare the accuracy of their proposed methods to determine the accurate food volume ,37,38,39Performance of feature extraction and classification techniques is highly dependent on the detail-oriented collection of images, which, in our case, happen to be food images. As consolidated large food image datasets, for example, UECFOOD-100, Food-101, UECFOOD-256, UNCIT-FD1200, and UNCIT-FD889 are eventually used as benchmarks to collate recognition performance of existing approaches with new classifiers. Such datasets can be distinctive in terms of characteristics, such as the total number of images in a particular dataset, cuisine type, and included food categories.For instance, UECFOOD-100 contains 100 different sorts of food categories, and each food category has a bounding box that indicates the location of the food item in the photograph. Food categories in this dataset mainly belong to popular foods in Japan . SimilarSeveral datasets mainly consist of various food images collected through various sources such as web crawlers and social media platforms such as Instagram, Flickr, and Facebook. Furthermore, most of these datasets contain images of foods that are specific to certain regions, such as Vireo-Food 172  and ChinTherefore, it is evident from the survey that there is an immense need for broad and generic food datasets for better food recognition and enhanced performance. This necessity is because region-specific food items or datasets with fewer food categories can undermine the accuracy and performance of classification and extraction methods.Feature extraction plays a vital role in automated food recognition applications due to its noticeable impact on the recognition efficiency of an employed system. Feature extractors methods extract different food image representations. The process of feature extraction involves the identification of visual characteristics like color, shape, and texture. The main objective of feature extraction is to reduce dimensionality space  and extrMoreover, selecting the right set of features ensures that relevant information is extracted from input images to perform the desired task. We categorized the feature extraction techniques into two main types: hand-crafted and deep visual features. The term ‘handcrafted’ refers to identifying relevant feature vectors of appropriate objects such as shape, color, and texture. In contrast to that, the deep model provides state-of-the-art performance due to automatic feature extraction through a series of connected layers. For this reason, recent studies have adopted combinations of both hand-crafted and deep visual features for food image representation.The existing literature exhibits a large number of methods to employ manually designed or handcrafted features. Handcrafted features are properties obtained through algorithms using help from information available in the image. The term ‘texture’ refers to homogeneous visual patterns that do not result from single colors such as sky and water . TexturaHoashi et al.  employedHowever, identification of food involves challenges due to varying recipes and presentation styles used to prepare food all around the globe, resulting in different feature sets . For insNonetheless, feature selection remains a complex task for food types that involve mixed and prepared foods. Such food items are difficult to identify and are not easily separable due to the proximity of ingredients in terms of color and texture features. In contrast, the evolution of deep learning methods has remarkably reduced the use of handcrafted features. This is due to their superior performance for both food categorization and ingredient detection tasks. However, handcrafted methods for feature extraction may still serve as the foundation for automated food recognition systems in the future.Recently, deep learning techniques have gained immense attention due to their superior performance for image recognition and classification. The deep learning approach is a sub-type of machine learning, and it trains more constructive neural networks. The vital operation of deep learning approaches includes automatic feature extraction through the sequence of connected layers leading up to a fully connected layer, which is eventually responsible for classification. Moreover, in contrast to conventional methods, deep learning techniques show outstanding performance while processing large datasets and have excellent classification potential ,94.Deep learning methods such as Convolutional Neural Networks (CNNs) , Deep CoAsymmetric multi-task CNN and spatial pyramid CNN  providesThe primary requirement of any food recognition system is accurate identification and recognition of food components in the meal. Therefore, robust and precise food classification methods are crucial for several health-related applications such as automated dietary assessment, calorie estimation, and food journals. Image classification refers to a machine learning technique that associates a set of unspecified objects with a subset (class) learned by the classifier during the training phase. In the scenario of food image classification, food images are used as input data to train the classifier. Hence, an ideal classifier must recognize any food category explicitly included during the learning phase. The accuracy of a classifier mainly depends on the quantity and quality of images, as there are several variations in food images such as rotation, distortion, lightning distribution, and so forth. In this section, we discuss classification techniques used by traditional approaches that use handcrafted features. Following that, we analyzed state-of-the-art deep learning models for food recognition.Major classifiers used by several traditional approaches in the domain of food image recognition include Support Vector Machines (SVM) , MultiplThe food recognition method proposed by  employs Chen et al. , employeDeep learning approaches have gained significant attention in the field of food recognition. This is due to their exceptional classification performance in comparison to traditional approaches ,64. convYanai and Kawano  employedClassification accuracy achieved was 77.4%, 76.3% and 54.7% for UECFOOD-100, UECFOOD-256 and Food-101, respectively. Over the past few years, nutritional awareness among people has increased due to their intolerance towards certain types of food, mild or severe obesity problems, or simply interest in maintaining a healthy diet. This rise in nutritional awareness has also caused a shift in the technological domain, as several mobile applications facilitate people in keeping track of their diet. However, such applications hardly offer features for automated food ingredient recognition.For this purpose, several proposed models use multi-label learning for food ingredient recognition. It can be defined  as the pFurthermore, Automated food volume assessment is a convoluted task involving various challenges. Highly diverse and varying compositions of food, increasing varieties of ingredients, and different methods of preparations are only some of the factors that need to be taken into consideration. Furthermore, the quality of pictures taken for food volume estimation also impacts the accuracy. Clear pictures taken in good lighting conditions would yield different results compared to low-resolution or low-light images. Thus, far, several methods have been proposed for accurate estimation of food volume ranging from simple techniques such as pixel counting to complex methods such as 3D image reconstruction. They have been broadly categorized as either ‘single image view’ or ‘multi-image/video view’ methods in the subsequent sections. Single-Image-View Methods for food volume estimation require only a single image for food volume estimation. These methods are relatively more user-friendly than ‘multi-image view methods’ because they do not require multiple images from different viewpoints. However, as a trade-off, most of the single-view methods are less accurate in contrast to multi-view methods. This method utilizes pixel count in each relevant image section to estimate food portion size. Studies  show thaThis method estimates visual similarities between a given image and an existing food image dictionary. It is used by many existing systems today , where tThis method projects a 3D model of food portions onto 2D space or uses 3D geometric models for volume estimation. Generally, this method gives finer approximation in contrast to the other methods for single-image-view methods.Other methods for food-portion estimation include estimating portion sizes using a ruler and adjustable wedge , mobile Multi-Image view or video methods require multiple images for food portion estimation. They are relatively more accurate than single-view-image methods. However, multi-image methods are less user-friendly as they require multiple images from different viewpoints in order to provide better results. This multi-image-view method uses a shape template method or 3D modeling for portion size estimation. As a single shape template is not suitable for all food types, the use of geometric models with correct food classification labels and segmentation masks in the image is important to index food labels to their respective classes of predefined geometric models. These can be used later for finding correct parameters of the selected geometric model ,41,56,62Moreover, in 3D modeling and pose estimation, models for food are constructed in advance by using between 15 and 20 food images captured from several angles or a video sequence. Finally, food volume is estimated by registering pose from 3D models to 2D images .The use of augmented reality is also being widely used by researchers to estimate food portion size. Many systems such as Eat AR make use of it for portion size estimation  by develSimilarly, the ‘Serv Ar’ augmented reality tool is used to provide guidance about food serving size . Many ofPortion estimation by constructing dense 3D models usually requires multiple images or a video segment . JoachimAutomatic food volume estimation method helps people to monitor their dietary intake suffering from chronic diseases without any expert intervention. It gives a quick result as compared to the traditional method which generally involves sending food images to the dietitian. The traditional method involves continuous involvement of dietitians, which makes it unworkable for dietitians to immediately respond to a large number of patients. Conversely, automatic food volume estimation is not standardized, as there are no existing guidelines by experts that refer to the error rate of these applications. Furthermore, different volume estimation methods vary in terms of accuracy and usability. Most of these methods are classified into two categories: single-image-view method and multiple-image-view method. Single-view-image methods are more user friendly, but their accuracy is compromised compared to multiple image view methods as it requires images from different. Therefore, standard guidelines are required for food volume estimation, which should include criteria for a balanced trade between features such as usability and accuracy, and developed applications must be verified according to the standard guidelines. We summarized the core applications of vision-based methods for food recognition in the context of public policy and health care.Today, several mobile applications have been developed to monitor diet and help users to choose healthier alternatives regarding food consumption. Initially, these mobile applications were dependent on manually inputting food items by selecting from limited food databases. Therefore, such applications were not very reliable as they were prone to inaccuracies in dietary assessment, mainly extending from limited exposure to numerous food categories. With the advancement in the area of food image recognition, a large number of mHealth applications for dietary assessment use images to recognize food categories. For this purpose, existing mobile applications use different combinations of traditional and deep visual feature extraction, and classification methods for food recognition described earlier in As the COVID-19 is a leading global challenge across the world, maintaining good nutritional status is mandatory for keeping good health to fight against the virus. Automatic vision-based methods for volume estimation and food image recognition in these nutrition tracking apps can assist patients in objectively measuring the nutrient intake of vital vitamins required for boosting the immune system.Life’s Simple 7 health score is recently introduced based on modifiable health factors that contribute to heart health. Physical activity, non-smoking status, healthy diet, and body mass index are four modifiable health behaviors in this score. The other three modifiable factors are biological. They include blood pressure, fasting glucose, and cholesterol details. Besides cardiovascular health, Life’s Simple 7 also relates to other health conditions such as venous thromboembolism, cognitive health, atherosclerosis, etc. As dietary intake plays a vital role in computing Life’s Simple 7, manually measuring these factors and then calculating a Life’s Simple 7 score is a very tedious process. This makes it very difficult for both middle-aged patients and elderly patients to keep track of their health. So vision-based methods can play an important role in automating the diet score. However, there are no current studies that have explored this research direction.Vision-based food recognition can automate the enforcement of an eating ban at public places by automatically detecting foods from CCTV and wearable cameras to curb the spread of the virus. Similarly, vision-based food recognition coupled with CCTV or wearable cameras and smart apps automate the enforcement of eating bans at workplaces, laboratories, etc.Coupling vision-based methods with wearable cameras can automatically detect foods from egocentric images with reasonable accuracy while reducing the burden of processing big data and addressing the user’s privacy concerns. Egocentric images acquired from these cameras are important to study diet and lifestyle, especially in low-income countries with a high malnutrition rate. For example, Jia et al.  focused We are in the era of social media, and food is a basic necessity of life, a great deal of content on social media platforms is related to food items. User’s of these platforms frequently share new recipes, new methods of cooking, food pictures after restaurant check-in. Researchers have exploited this data on social media platforms for analyzing dietary intake. For example, Mejova et al.  studied Evaluating fruit quality and freshness at the marketplace and at the user end is of increasing interest as opposed to accessing quality at the time of manufacturing. Efforts to date have focused on accessing the quality of foods using vision-based methods. For example, Ismail et al. have contributed an Apple-NDDA dataset  that conWe provide a statistical analysis of our study based on the articles and conference proceedings gathered to write this survey paper. We surveyed research studies up to 2020 from various reputed sources: IEEE, Elsevier, ACM, and Web of Sciences. This study highlighted open issues based on the survey papers and the authors’ first-hand experience with existing methodologies.Preparing a large comprehensive annotated data is still a challenge, as manually annotating a dataset is a difficult task with many challenges. Due to the large variety of food dishes, different styles of preparation, etc., it is difficult for an expert dietician to correctly label all the foods, especially in the preparation of a multi-culture food database. Similarly, it involves high costs and a large number of working hours to prepare such a dataset. Recent advancements in contrastive learning have opened a new research paradigm of unsupervised learning. Methods based on contrastive learning such as SimCLR  and SwAVFood datasets are open-ended, and there is no cap on the number of dishes. So the network must adapt to continuously evolving datasets. All of these properties of food datasets have made them a strong use case for continual learning methods. One of the principal challenges in continuous learning methods is catastrophic forgetting. Catastrophic forgetting refers to completely or abruptly forgetting previously learned information while learning new classes. Many neural networks are susceptible to forgetting during continual learning. It is a prime hindrance in achieving the objective of continuously evolving networks similarly to those of humans. Hence, researchers should also study catastrophic forgetting in the context of food databases.Although there have been numerous attempts, including activation methods, SHAP values , and disOur research provides deep insight into computer vision-based approaches for dietary assessment. It focuses on both traditional and deep learning methodologies for feature extraction and classification methods used for food image recognition and single- and multi-view methods for volume estimation. Similarly, this survey also explores and compares current food image datasets in detail, as vision-based techniques are highly dependent on a comprehensive collection of food images. In contrast to previous research work, such as work by Mohammad A. Sobhi et al. , Min, WeOur findings indicate that the ultimate performance of traditional and deep visual techniques depends on the type of dataset used. This has been observed from the datasets included from the studies explored in this survey (as shown in Finally, food category recognition, ingredient classification, and volume estimation techniques helped provide an automatic dietary assessment with reduced human intervention in mHealth apps. For this purpose, we have also surveyed several mobile applications that employ deep learning methods for dietary assessment.Despite enhanced performance and classification accuracy, food image recognition and volume estimation through vision-based approaches may continue to present interesting future research challenges. This is because the performance of the methodologies used for food image identification is highly dependent on the source of images in a particular food dataset. Although a growing number of food categories are being incorporated into food image datasets such as UECFOOD-256 , Food 85In addition to this, progressive learning during the classification phase is vital for food image datasets due to the continuous arrival of new concepts and domain variation within existing concepts. Similarly, developing frameworks interpretable by highlighting the contribution of the area of interest will improve the overall human trust level on a solution in a real-world environment.Following food recognition, food volume estimation is a particularly complex and challenging assignment since food items have large variations in shape, texture, and appearances. Our article categorized food portion estimation methods into single-view and multi-view methods. Multi-view methods are more accurate; however, most of these methods also require calibration objects each time and images from different viewpoints, which makes the usability of these solutions tedious for elderly users.Finally, there is a need to design and develop solutions that can respond to situations ethically. In our context, this refers to the removal of any biases concerning region-specific food preferences. It will help to ensure transparency in existing models.In this work, we explored a broad spectrum of vision-based methods that are specifically tailored for food image recognition and volume estimation. In practice, the food recognition process incorporates four tasks: acquiring food images from the corresponding food datasets, feature extraction using handcrafted or deep visual, selection of relevant extracted features, and finally, appropriate selection of classification technique using either traditional machine learning approach or deep learning models followed by food ingredient classification to provide better insight of nutrient information. The findings of surveyed studies have shown that 38.1% of datasets are generic, which includes multi-cultural food dishes. Similarly, 46.2% of surveyed applications implemented CNN for food recognition, while 45.2% of mobile applications have implemented traditional methods for feature extraction. For ingredient detection, several studies used CNN due to its superior performance and recent interest. In addition, 34.5% of techniques for volume estimation require multiple images, while the remaining methods used a single image to estimate food volume.Despite impeccable performance exhibited by state-of-the-art approaches, there exist several limitations and challenges. There is an immense need for comprehensive datasets for benchmarking and performance evaluation of these models, as incorporating large food image datasets improves the overall performance. Consequently, when dealing with open-ended and dynamic food datasets, the classifier must be capable of open-ended continuous learning. However, existing methods have several bottlenecks, which undermine the food-recognition ability when it comes to open-ended learning, as proposed methods are prone to catastrophic forgetting. They tend to forget previous knowledge extracted from images while learning new information. Such methods work well only for fixed food image datasets. Moreover, our findings indicate that proposed techniques for food ingredient classification still struggle with performance issues when applied to prepared and mixed food items. Survey findings further indicate that CNN models employed for visual feature extraction require labeled datasets for fine-tuning and training. Preparing a labeled food dataset is a difficult task due to the large variety of food dishes. To tackle this problem, unsupervised methods based on contrastive learning seem to have good research potential.Similarly, automatic food portion estimation methods are categorized into two major categories: single-view-image methods and multi-view-image methods. As discussed earlier, most of multi-view image methods are more accurate than single view methods, but multi-view-image methods require complex processing and images from different angles, resulting in a reduced user retention rate. Furthermore, most of the single and multi-view methods require calibration objects each time, which has made the usability of these solutions tedious for elderly patients.Therefore, there is substantial room for innovative health care and dietary assessment applications that can integrate wearable devices with a smartphone to revolutionize this research area. Moreover, dietary assessment systems should address these challenges to provide better insights into effective health maintenance and chronic disease prevention.


Oral administration is an appealing route of delivering cancer treatments. However, the gastrointestinal tract is characterized by specific and efficient physical, chemical, and biological barriers that decrease the bioavailability of medications, including chemotherapeutics. In recent decades, the fields of material science and nanomedicine have generated several delivery platforms with high potential for overcoming multiple barriers associated to oral administration. This review describes the properties of several nanodelivery systems that improve the bioavailability of orally administered therapeutics, highlighting their advantages and disadvantages in generating successful anticancer oral nanomedicines. The primary factor determining drug pharmacokinetics and proper concentration at the target site is the administration route. Despite known drawbacks like low drug bioavailability, high degradation, and intestinal and hepatic metabolism, oral treatments have always been considered the most convenient way to deliver a pharmaceutic. This clinical dogma is generally applied to any pathological condition, and most of the approved therapeutics on the market are designed for oral administration  Fig. 1)1). Oral Some benefits of oral chemotherapy over standard drug administration routes remain to be proven , and patThis review focuses on nanotechnologies tested for oral chemotherapy, highlighting their characteristics for overcoming specific and multiple GIT biological barriers. Some of these barriers also need to be addressed when treating GIT tumors, common and lethal diseases affecting nearly every section of this organ system. Before describing recent examples of oral nanomedicine, a general description of GIT biological barriers and the techniques used to measure intestinal absorption is paramount.Different tissue, cellular, physical, and biological components regulate GIT barrier function. The buccal cavity may be an optimal site for drug administration, considering its mildly acidic environment and high submucosal and sublingual space vascularization. However, the transit time of pharmaceutics in the buccal cavity is usually very brief. Therefore GIT remains the primary absorption site for orally administered pharmaceutics .The GIT is a muscular tube 6–10 m long. It is organized into various anatomical regions grouped into 2 two parts: the upper  and the lower section . Nutrient and pharmaceutic absorption varies in the different sections of the GIT. The stomach is the site where the food is broken down and is characterized by small surface area, limited nutrient (and drug) absorption, and very low pH (between 1.5 and 2.5) representing the first chemical barrier encountered by oral pharmaceutics sensitive to acidic pH. However, stomach pH can increase significantly (up to 4–5) after a meal. The small intestine is characterized by slightly acidic pH (5–7.5) that increases in the large intestine (up to 8) . GIT epiEnzymatic degradation is another significant biochemical barrier, particularly for biologics. Pepsin, a broad-range protease, is the main enzyme of the stomach. However, other digestive enzymes, like lipases, are also secreted, and in general, enzymatic composition varies in different GIT sections. In the small intestine, pancreatic and hepatic enzymes break down carbohydrates and nucleic acids in addition to proteins and fatty acids. Mucus is also necessary to provide the ideal environment for enteric microflora proliferation and survival that can change with age, diet, GIT location, and pathological conditions (dysbiosis) . From a The main factors that govern GIT absorption are the surface area of the tissue, tissue vascularization, water solubility, physical state , and concentration of the pharmaceutical at different absorbing sites, . In termThe last barrier is the membrane of the cells lining the GIT. Of these, enterocytes are recognized as the main absorption elements. Nutrients and therapeutics can overcome the epithelial barrier in five distinct ways that can be grossly grouped as active and passive transport. Paracellular and transcellular diffusion are considered passive ways of transport, while receptor-mediated, carrier-mediated, and microfold cell (M-cell)-mediated passage are considered active transport. M-cells, along with enterocytes and some goblet cells, compose the follicle-associate epithelium covering Peyer’s patches, lymphoid structures that are the primary immune system components of the GIT. M-cells have strong engulfment potential and sort pathogens, bacteria, and viruses destined for the components of the underlying immune system , 33. NotP value of a molecule, which is a direct measure of its liposolubility. Log P is directly related to the molecule's ability to diffuse through the cell membrane and indirectly related to its ability to diffuse in GIT fluids [Paracellular transport mechanisms are regulated by epithelial tight junctions, adherens junctions, and desmosomes. The GIT epithelium is permeable only to very small molecules and ions (8–13 Å), with an estimated paracellular cut-off below 2 nm. When the junctions open, this passage can increase to 18 nm, while the underlying layers are impermeable to elements larger than 13–15 nm . TransceT fluids . Net oraA general schematic of the major biological barriers hampering oral drug delivery is shown in Fig. Different levels of research models are used investigate the absorption of any therapeutic in the GIT environment. Computational models have been generated to predict intestinal drug absorption , but unf2) [Protocols based on simulated intestinal fluids are widely used to investigate the potential of nanomedicine for oral drug delivery. Loaded particles are usually incubated in these buffers to evaluate their stability and drug release properties in the GIT. Simulated GIT fluids are characterized by specific pH, bile salt, and enzyme concentrations to represent the different compartments of the gastrointestinal system. Some procedures describe protocols for generating gastric fluids that simulate fasted and fed conditions, since pH and enzymatic content can vary significantly in these states . The hum2) . Caco-2 2) . Molecul2) , 46, an 2)  2, CO2, pH, and transepithelial electric resistance (TEER) measurements, and are ideal for investigating epithelial perfusion under more complex conditions [Organ-on-a-chip systems represent further advances in the field, and in this case, they are referred to as gut-on-a-chip (GoC). In GoC, the goal is to increase system complexity, including elements like microbiota and endothelial and immune cells , 49. Othnditions .Fig. 5GuEx-vivo models are based on isolating different sections of the intestine, and barrier integrity and absorption can be investigated in everted  and non-In situ protocols are performed in vivo by isolating intestinal sections via ligation and locally injecting the molecule of interest. Absorption is then measured in the blood of the subject animal. The physiology of the animal is preserved and absorption can be investigated in specific GIT sections. We recommend the following reviews for more in-depth information of ex situ and in situ procedures , 52, 54.The use of nanoparticles to enhance oral drug delivery is supported by recent evidence that highlights their versatility and ability to load different therapeutics. Encapsulation can provide a means to increase drug solubility, while particle surface properties can facilitate the penetration of the physical barriers of mucus and epithelial cell membranes. Drug encapsulation also protects the therapeutic payload from the harsh gastric chemical and enzymatic conditions and allows controlled release, which may be helpful for maintaining proper therapeutic concentrations. Finally, nanocarriers allow co-encapsulation of more than one molecule to simultaneously deliver synergistic pharmaceutics that work more precisely together than when administered singularly. Carriers can be generated from biological and organic materials, although inorganic materials and hybrid systems are also routinely tested for this purpose. Each material provides unique features to favor drug encapsulation, protection, and GIT translocation in the bloodstream and the lymphatic system. These features will be described in the following sections, emphasizing the nanoparticle properties that allow negotiation of the GIT biological barriers.+-coupled organic cation/carnitine transporter 2 (OCTN2), expressed in the lumen of the small intestine, to enhance the delivery of paclitaxel [+ in a 1:1 ratio, particle uptake increased in the presence of Na+. This evidence was confirmed in vivo by administering free and encapsulated paclitaxel via in situ single-pass perfusion. When the therapeutic was administered via PLGA nanoparticles modified with carnitine, higher drug bioavailability was observed; this was also because particle internalization reduced the effect of P-gp, which strongly inhibits paclitaxel. Optimized Na+ concentration further improved the process, while free carnitine significantly decreased particle uptake, indicating that these particles must be administered in parallel, with diets containing a certain amount of sodium and no carnitine for reaching optimal therapeutic performance. Finally, the group discovered that much of the absorption occurred in the lymphatic system, suggesting that a certain number of particles can overcome the epithelial barrier via a caveolin-mediated pathway, probably due to OCTN2 receptor recycling. PLA nanoparticles are FDA approved and show high biocompatibility, safety, and sustained drug release [This section refers to organic polymers like polyglycolic acid, polymethylmethacrylate, polylactic acid (PLA), poly(lactic-co-glycolic acid) (PLGA), and poly(ε-caprolactone). These materials have the great advantage of being almost entirely biocompatible and resistant to the GIT environment. Methacrylic co-polymer coating (Eudragit) is commonly used to stabilize oral pharmaceutical formulations like tablets and capsules, and more recently, they have been shown to improve stability of liposomal formulations . For thiclitaxel . Charact release . However release  can miti release , potenti release .Pharmacokinetic properties of hydrophobic chemotherapeutics like paclitaxel can be improved by modifying PLA particles with folic acid, since the GIT epithelium has significant expression of folate receptors . Folate Polycaprolactone (PCL) is another polymer for generating biocompatible nanoparticles for delivering different chemotherapeutics, including docetaxel , cisplatCurrently, several inorganic materials can be used to generate nanoparticles with different uses and properties. Some of these properties perfectly fit with the scope of engineering nanoparticles for oral administration. Generally, inorganic nanoparticles are considered more stable at body temperatures and acidic conditions, even though some materials are entirely soluble at low pH. Between them, silica nanoparticles were significantly investigated to improve oral delivery of therapeutics. Silica is generally considered biocompatible  and easyBacillus licheniformis and tested in vitro for their anti-cancer effects and toxicity. In vivo, compared to commercial selenium supplements, these nanoparticles demonstrated reduced toxicity, probably due to the biological origin of the nanoparticles that increased their biocompatibility. However, when the authors tested the particles in vivo, compared to commercial selenium sources, they saw reduced drug absorption that could partially explain reduced systemic toxicity [Another element that can be used for oral nanomedicine is selenium. Its anti-cancer properties are well known, and physiological levels of selenium have high cancer prevention potential . Howevertoxicity .Polysaccharides are amphiphilic molecules and provide good wetting properties to overcome the mucus barrier, in addition to their natural ability to encapsulate anti-tumor therapeutics. They are isolated from different biological sources, including animals (chitosan), algae , plants (pectin), and bacteria (dextran). They are biocompatible, generally easy to manipulate on the nanoscale, and extensively used for pharmacological formulations. As with other nanoformulations, polysaccharide nanoparticles demonstrate the ability to inhibit efflux pump activity , and in Another polysaccharide extensively used to generate oral nanomedicine is cyclodextrin, which very efficiently encapsulates hydrophobic drugs , and can block efflux pump activity . CyclodeProtein carriers formulated from poly-amino acid chains, gelatin, collagen, casein, and albumin are a few examples of this category. These molecules have amphipathic properties and are ideal for accommodating payloads with different chemical and physical features. M-cells could represent a natural gate for protein nanoparticle transport across the GIT epithelium since they translocate antigens to the underlying lymphoid tissues . TheoretThe synthetic protocols used to generate protein nanoparticles can affect their stability against enzymatic degradation. Albumin carriers generated via desolvation are more prone to pepsin degradation than particles synthesized via emulsification, probably due to differential access of pepsin to cleavable peptide bonds . In addiMoreover, the surface of protein carriers allows multiple sites of chemical modification to increase accumulation of these particles at the intestinal epithelium level, where they can release the payload or, in the case of GIT tumors, improve carrier specificity to target tumor cells. Interestingly, nanoparticles composed of apotransferrin and lactoferrin efficiently increased doxorubicin accumulation in hepatic cancer after oral delivery even though the authors did not investigate the particle/payload absorption mechanism . HoweverAs in many cases discussed in this review, generation of nanomedicine for oral drug delivery is often driven by the need to enhance oral bioavailability of a therapeutic agent. For example, resveratrol, a hydrophobic polyphenol found in wine, shows significant therapeutic effects in cardiovascular disease treatment and cancer prevention. However, its bioavailability when orally administered is very low (less than 5%) due to its high excretion rate and hepatic and intestinal metabolism . Also, iLipid nanoparticles  enhance hydrophobic drug encapsulation solubility, but when used for oral administration, they are often engineered in hybrid formulations to increase their stability in the GIT environment. However, some studies indicate that when interacting with bile salts, liposomes can generate vesicles and micelles that can be absorbed in the upper section of the GIT via transcytosis , 100. HyThe group of Dr. Chen developed polymer(pegylated PLGA)-stabilized lipid nanoparticles to increase the oral bioavailability of berberine, a vegetal molecule with numerous therapeutic properties that include anti-neoplastic activity . Oral adNucleic acids like short interfering RNAs (siRNA) and long interfering RNAs are a class of biologics that would greatly benefit from oral delivery, but are sensitive to the harsh gastric environment and cannot cross the GIT epithelium . Ball etIn this section, we discuss carriers that can be grown or isolated in nature without extensive bottom-up synthetic procedures and that can be exploited for drug delivery purposes. Of these, microorganisms and exosomes have particular features that are functional for developing oral drug delivery while maintaining precise characteristics on the nanoscale. Microorganisms represent the last frontier for the development of oral nanomedicine since they can specifically target M-cells , 112 andGiardia lambia in the GIT tract of mammals. Modifying the surface of retrovirus-like particles with these proteins determined their GIT stability and allowed immunization against influenza virus hemagglutinin (HA). More importantly, this vaccine induced an immune response against a transgenic mesothelioma tumor expressing HA. VSP coating was also shown to increase the immunogenicity of the system, providing a natural adjuvant for immunization. The authors demonstrated that this approach could provide a solid protocol for generating an oral vaccine for cancer when directed against proper antigens [Microorganisms can also serve as the perfect basis for developing orally administrable cancer vaccines . Cysteinantigens .Salmonella bacteria were coated with cationic polymeric nanoparticles condensed with DNA to generate an oral cancer vaccine [Salmonella bacteria were coated spontaneously via electrostatic interactions between the positively charged nanoparticles and the negatively charged surface of the bacteria. The authors demonstrated that this coating efficiently protected the attenuated bacteria from the gastric environment, favoring their distribution in the blood and the lymphatic tissue. The bacteria also efficiently mediated anti-cancer immunity via T cell activation (CD4 and CD8) and cytokine secretion. Immune system activation occurred due to VEGFR2 antigen expression on phagocytic cells after particle escape from the endosomal compartment (Fig. Similarly, live attenuated  vaccine . The sysent Fig. .Fig. 9SyMilk exosomes –121 possGIT tumors are common, often lethal diseases, affecting nearly every section of this organ system. When designing oral nanomedicines for these anatomical sites, it is essential to consider particle stability when targeting the lower GIT and particle adhesion properties when targeting the upper GIT. Oral mucositis is a common condition in cancer patients and often limits the continuity of anticancer therapies, forcing physicians to resolve this issue before continuing other treatments. PLGA nanoparticles were recently developed for treating mouth lesions caused by chemotherapy . They weThe high adhesion properties of polydopamine nanoparticles  inspiredFinally, it is worth mentioning the work of Xu et al. , who genAbsorption is the limiting factor for developing efficient oral chemotherapy, particularly for new high molecular weight molecules like biologics , 133. Pa


Mitochondria are specialized organelles involved in energy production that have retained their own genome throughout evolutionary history. The mitochondrial genome (mtDNA) is maternally inherited and requires coordinated regulation with nuclear genes to produce functional enzyme complexes that drive energy production. Each mitochondrion contains 5–10 copies of mtDNA and consequently, each cell has several hundreds to thousands of mtDNAs. Due to the presence of multiple copies of mtDNA in a mitochondrion, mtDNAs with different variants may co-exist, a condition called heteroplasmy. Heteroplasmic variants can be clonally expanded, even in post-mitotic cells, as replication of mtDNA is not tied to the cell-division cycle. Heteroplasmic variants can also segregate during germ cell formation, underlying the inheritance of some mitochondrial mutations. Moreover, the uneven segregation of heteroplasmic variants is thought to underlie the heterogeneity of mitochondrial variation across adult tissues and resultant differences in the clinical presentation of mitochondrial disease. Until recently, however, the mechanisms mediating the relation between mitochondrial genetic variation and disease remained a mystery, largely due to difficulties in modeling human mitochondrial genetic variation and diseases. The advent of induced pluripotent stem cells (iPSCs) and targeted gene editing of the nuclear, and more recently mitochondrial, genomes now provides the ability to dissect how genetic variation in mitochondrial genes alter cellular function across a variety of human tissue types. This review will examine the origins of mitochondrial heteroplasmic variation and propagation, and the tools used to model mitochondrial genetic diseases. Additionally, we discuss how iPSC technologies represent an opportunity to advance our understanding of human mitochondrial genetics in disease. The final OXPHOS complex, ATP synthase, harnesses the electrochemical gradient to produce cellular ATP . Th. Th78]. DNAJC19 gene (rs137854888). The iPSC-derived cardiomyocytes carrying the DNAJC19 gene mutation had differential levels of cardiolipin species and mitochondrial fragmentation, pathophysiological signs previously associated with dilated cardiomyopathy with ataxia (DCMA), a phenotype often diagnosed with Barth syndrome. Treatment with SS-31 in part restored mitochondrial networks [CRISPR-Cas9 editing, it does reveal the utility of human iPSC-derived cardiomyocytes harboring mitochondrial genetic variants in studying the mechanisms of mitochondrial disease. As aforementioned, the additional application of CRISPR-Cas9 will allow scientists to effectively model variants that are difficult to obtain from patient populations; for example by editing normal iPSCs to introduce variants of uncertain significance that have been hypothesized to result in mitochondrial dysfunction. Importantly, for mitochondrial mutant models that do exist from patients, many have yet to be phenotypically validated [One study has demonstrated the utility of using iPSC-derived cardiomyocytes for screening novel therapeutic strategies in mitochondrial cardiomyopathy. iPSC-derived cardiomyocytes were generated from pediatric patients carrying a loss of function mutation in the networks , althougene rs1374888. TheWhile mitochondrial cardiomyopathy only represents one clinical presentation of mitochondrial mutations, the opportunities for modeling mitochondrial disease are ex-pansive. Just as many iPSC models of nDNA mutants have been created to model human disease ,86,87,88Despite the advantages conferred over animal models and primary human tissues, iPSCs have several limitations in their ability to model mitochondrial disease. First, while iPSCs possess the ability to differentiate into any cell type, some mitochondrial mutations disrupt the differentiation process, particularly directed differentiation toward highly energetic cell types . If a giIn addition to the limitations in genetic modeling and differentiation, iPSCs that are successfully differentiated do not always possess the characteristics of the fully-mature adult cell type, retaining a more fetal-like phenotype. For example, while iPSC-derived cardiomyocytes contract and express cardiac muscle-specific genes, they lack adult metabolic phenotypes and calcium handling properties ,91,92. IMitochondrial disease pathobiology remains incompletely understood due to the absence of disease models. We posit that the recent advancements in human iPSC technology, in conjunction with CRISPR-Cas9 targeted gene-editing techniques, will significantly extend our ability to systematically investigate the effect of individual or combinations of nDNA or mtDNA-encoded mitochondrial gene mutations, on mitochondrial function in various adult cell types. The use of multi-omics approaches, particularly at the single cell level in iPSCs, positions the iPSC to be an effective model system for mitochondrial metabolic disorders. Moreover, the ease of iPSC-based screening assays for environment-gene interactions will enhance our understanding of the effect of these interactions on cell phenotypes. Advancement in our understanding of mitochondrial pathobiology will aid in the identification of therapeutic targets in the management of what are currently difficult diseases to treat. Our enhanced understanding will enable drug screening assays that include patient-specific human genetic backgrounds in adult cell types and are likely to identify novel treatment strategies .


Introduction: The world’s opioid epidemic has gotten increasingly severe over the last several decades and projects to continue worsening. Orthopedic surgery is the largest contributor to this epidemic, accounting for 8.8% of postoperative opioid dependence cases. Total knee arthroplasty (TKA) and anterior cruciate ligament (ACL) reconstruction are commonly performed orthopedic operations heavily reliant on opioids as the primary analgesic in the peri- and immediate postoperative period. These downfalls highlight the pressing need for an alternate, non-pharmacologic analgesic to reduce postoperative opioid use in orthopedic patients. The presented systematic review aimed to analyze and compare the most promising non-pharmacologic analgesic interventions in the available literature to guide future research in such a novel field. Methods: A systematic search of PubMed, MEDLINE, Embase, Cochrane, and Web of Science was performed for studies published before July 2020 based on the PRISMA  guidelines, and the obtained manuscripts were evaluated for inclusion or exclusion against strict, pre-determined criteria. Risk-of-bias and GRADE  assessments were then performed on all included studies. Results: Six studies were deemed fit for inclusion, investigating three non-pharmacologic analgesics: percutaneous peripheral nerve stimulation, cryoneurolysis, and auricular acupressure. All three successfully reduced postoperative opioid use while simultaneously maintaining the safety and efficacy of the procedure. Discussion: The results indicate that all three presented non-pharmacologic analgesic interventions are viable and warrant future research. That said, because of its slight advantages in postoperative pain control and operational outcomes, cryoneurolysis seems to be the most promising. Further research and eventual clinical implementation of these analgesics is not only warranted but should be a priority because of their vast potential to reduce orthopedics surgeries’ contribution to the opioid epidemic. Total knee arthroplasty (TKA) and anterior cruciate ligament (ACL) reconstruction surgeries are two of the most performed orthopedic operations in the world –4. TKA cWhile both procedures are considered highly efficacious, with TKA having shown a 10- to 15-year implant survivorship rate of over 90% , and up According to Li et al. 2019 review, a multimodal approach is currently considered best practice for TKA pain management , 8. ThisThe main downfall of both approaches is the heavy reliance on opioids, a strong and addictive class of painkillers associated with massive negative side effects . OpioidsAdditionally, the United States is in the middle of the world’s largest opioid epidemic –18, singThe current multimodal analgesic approach mentioned above for both TKA and ACL reconstruction has attempted to combat this epidemic by lessening opioid use –11; howeThe combination of the opioid epidemic and lack of viable alternative, long-term pharmacologic analgesics highlights the demanding need for a non-pharmacologic analgesic intervention in the perioperative period. An alternative non-pharmacologic analgesic working to the same efficacy as opioids and NSAIDs could, in theory, completely replace said drugs to manage pain in TKA and ACL reconstruction operations, ending orthopedic surgeries’ large contribution to the United States opioid crisis.All of that said, non-pharmacologic perioperative analgesia is a very novel field of research, and the current literature is very limited. This systematic review intended to highlight and synthesize the available literature in the field, aiming to serve as a template for future research, effectively speeding up the process of establishing an efficacious non-pharmacologic analgesic for major knee surgery.In doing so, the effectiveness of percutaneous peripheral nerve stimulation, percutaneous cyroneurolysis (percutaneous freezing of sensory nerves), and auricular acupressure were comparatively evaluated.A systematic search of the published literature was performed based on PRISMA  guidelines for studies published before July 9th, 2020.).ti,ab) AND  AND (exp Arthroplasty/)) OR TKA.ti,ab OR (knee adj2 (replacement* OR arthroplast*)).ti,ab) OR  AND ))) AND ).ti,ab OR exp Perioperative Care/ OR exp Perioperative Period/)A Medical Subject Heading (MeSH) plus keyword search was performed across PubMed, MEDLINE, Embase, Cochrane, and Web of Science. The MEDLINE search was conducted as follows:The articles obtained were then evaluated based on strict inclusion and exclusion criteria. Studies were included that focused on (1) analyzing the efficacy of a non-pharmacologic peri- or immediate postoperative intervention for TKA or ACL reconstruction operations, (2) analyzing the effect of said interventions on short and long-term postoperative opioid use, (3) analyzing the clinical and functional outcomes of procedures in patients treated with said interventions, and (4) used human patients.Studies were excluded based on the following criteria: (1) focusing on operations other than TKA or ACL reconstruction; (2) focusing on patients who were previously diagnosed with opioid addiction; (3) analyzing the efficacy of a pharmacologic (drug-based) intervention; (4) analyzing the efficacy of a non-pharmacologic intervention used in the rehabilitation phase (after the immediate postoperative period).All studies were screened independently based on the previously stated criteria. Articles were screened initially by title and then abstract, after which the full text of all remaining manuscripts was reviewed. All full-text manuscripts determined as meeting criteria were included for analysis.The primary outcome of interest in the presented study was patients’ postoperative opioid use. Secondary outcomes of interest includes non-opioid postoperative medication use, pain scores, and clinical and functional surgical outcomes. These measures were intended to determine the ramifications of non-pharmacologic analgesia usage on the effectiveness of each operation.Each of the six included studies was also assessed for risk-of-bias: randomized controlled trials (RCTs) were assessed using the Revised Cochrane Risk-of-Bias Tool for Randomized Trials , case seSubsequently, the overall body of evidence was assessed using the GRADE  criteria for each primary and secondary outcome. As such, the authors evaluated the evidence for each outcome based on study type, risk-of-bias, and the precision, consistency, and directness of the data. All GRADE assessment categories and outcomes evaluated can be seen in Database searches resulted in a total of 1902 publications to be screened. Initially, duplicates were removed, resulting in 1354 remaining papers. These papers were first screened by title – where 1116 papers were excluded, then abstract – where 211 more papers were excluded. Finally, full-text manuscripts of the remaining 27 publications were screened, and 6 were deemed to fit inclusion criteria. The six included studies consisted of two RCTs , 28, thrGRADE quality of evidence was assessed for five separate outcomes: postoperative opioid use, other postoperative analgesic use, pain scores, clinical outcomes, and functional outcomes. The quality of evidence was rated as “low” for all, primarily due to the small sample sizes of most included studies, and all outcomes were graded as either “critical” or “important” .Five included studies investigated the effects of non-pharmacologic analgesics on TKA patients , 29–32, Three of these studies investigated the efficacy of percutaneous peripheral nerve stimulation, two percutaneous cryoneurolysis, and one auricular acupressure . Lastly,As seen in All three non-pharmacologic interventions proved successful at reducing postoperative opioid consumption. That said, the most overall success was seen in the Ilfeld et al. percutaneous peripheral nerve stimulation study, in which they showed a median time to opioid cessation of only six days .Only Ilfeld et al. in 2018 reported on other pharmacologic analgesic medication usage, showing that 7/10 patients elected to turn on a canal nerve block to supplement non-pharmacologic treatment. However, the same paper also showed more encouraging data in that 8/10 patients elected to use an optional perineural injection analgesic on postoperative days (POD) 1 and 2, but only 3/10 patients still required the same treatment on POD 3 , suggestAll six included studies showed their respective interventions to be successful analgesics as measured by postoperative pain scores –32. OnlyClinical outcomes should be considered very important secondary outcomes for novel non-pharmacologic perioperative analgesics because it ensures that any successes with respect to reduced opioid consumption and pain management do not come at the expense of the primary operational goal. Four included studies reported data on the clinical outcome of each operation , 30, 32.Functional outcomes of each operation were also analyzed as a secondary outcome. Five out of six studies reported such data –31. As dCryoneurolysis, percutaneous peripheral nerve stimulation, and auricular acupressure all have the capability to successfully reduce postoperative opioid use in major knee surgery –32. WhilTime to cessation of opioid use is an extremely important measure of non-pharmacologic analgesic success because opioid use of more than 31 days postoperatively is associated with a greater likelihood of chronic opioid use one year after surgery . All nonSimilarly, cryoneurolysis and percutaneous peripheral nerve stimulation reduced postoperative pain scores earlier in the perioperative period than did auricular acupressure –32. AuriIt is inherently important to ensure any novel analgesic does not negatively affect surgical outcomes. As such, it is of great significance that none of the presented non-pharmacologic interventions worsened clinical or functional outcomes following major knee surgery –32.One major difference is noteworthy in that cryoneurolysis was the only modality to show improved clinical outcomes over a control group ; with siAs alluded to above, cryoneurolysis, percutaneous peripheral nerve stimulation, and auricular acupressure appear to all be viable analgesic interventions for TKA and ACL reconstruction surgeries. That said, the presented data suggest that cryoneurolysis, closely followed by percutaneous peripheral nerve stimulation, maybe the most beneficial to implement in clinical settings.Cryoneurolysis is the most successful intervention at inhibiting peri- and postoperative pain , 32. BotWhile considering all the presented data, it is also important to recognize the limitations of each study. Most limitations in the presented systematic review stem from the novelty of perioperative non-pharmacologic analgesic research. The largest overall limitation is the small number of suitable studies and small sample sizes investigated in said studies. As shown in As highlighted in the Introduction section, the primary benefit of a successful perioperative non-pharmacologic analgesic would be to replace opioids as the primary postoperative analgesic in major knee surgery. Doing so would eliminate the vast negative effects of opioid use, including concerningly high misuse and abuse rates in prescribed users and a high frequency of adverse side effects . MoreoveFuture research into perioperative non-pharmacologic analgesics is certainly warranted. The first and most telling research that should be performed is to implement full-scale, multi-site RCTs for cryoneurolysis and percutaneous peripheral nerve stimulation. While the data from pilot studies are very promising, RCTs would drastically improve the reliability of results seen and overcome the available literature’s current issue with small sample sizes. Moreover, it would be very telling to measure longer-term follow-ups, allowing researchers to determine if there are any negative long-term effects on nerve function from either cryoneurolysis or percutaneous peripheral nerve stimulation. Although studies utilizing cryoneurolysis to treat chronic pain have shown it to be safe and reversible over time , so compOther interesting extensions of the presented studies would be determining if an additive or synergistic effect can be seen by simultaneously implementing auricular acupressure and either cryoneurolysis or percutaneous peripheral nerve stimulation. Lastly, a notable distinction exists in the presented papers evaluating cryoneurolysis and percutaneous peripheral nerve stimulation that some utilize ultrasound guidance for implementation, and some do not. While it seems reasonable that ultrasound guidance is safer and allows for more detailed lead placement, similar results were seen in the presented review for studies including or excluding ultrasound guidance. Hence, a trial directly comparing outcomes for these groups would be important in setting clinical best practices.The present systematic review aimed to analyze and compare the available literature on perioperative non-pharmacologic analgesic interventions in the hopes of advancing a novel field of orthopedic research, with the end goal of lessening postoperative opioid use after TKA and ACL reconstruction operations. As such, the authors conclude that cryoneurolysis, percutaneous peripheral nerve stimulation, and auricular acupressure all appear to be viable and successful non-pharmacologic analgesics in the perioperative period. Of the three, cryoneurolysis seems the most promising moving into future research.R. Juncker: The author declares that they have no relevant financial or non-financial interests to report.F. Mirza: The author declares that they have no relevant financial or non-financial interests to report.J. Gagnier: The author declares that they have no relevant financial or non-financial interests to report.This research did not receive any specific funding.Ethical approval was not required.This article does not contain any studies performed by the authors involving human subjects.Conceptualization, Methodology, Investigation, Writing original draft, Reviewing and Editing; F. Mirza: Conceptualization, Methodology, Investigation, Reviewing and Editing; J. Gagnier: Conceptualization, Methodology, Investigation, Reviewing and EditingR. Juncker: