Following the advancementsand diversification in synthetic strategiesfor porous covalent materials in the literature, the materials sciencecommunity started to investigate the performance of covalent organicpolymers (COPs) and covalent organic frameworks (COFs) in applicationsthat require large surface areas for interaction with other molecules,chemical stability, and insolubility. Sensorics is an area where COPsand COFs have demonstrated immense potential and achieved high levelsof sensitivity and selectivity on account of their tunable structures.In this review, we focus on those covalent polymeric systems thatuse fluorescence spectroscopy as a method of detection. After brieflyreviewing the physical basis of fluorescence-based sensors, we delveinto various kinds of analytes that have been explored with COPs andCOFs, namely, heavy metal ions, explosives, biological molecules,amines, pH, volatile organic compounds and solvents, iodine, enantiomers,gases, and anions. Throughout this work, we discuss the mechanismsinvolved in each sensing application and aim to quantify the potencyof the discussed sensors by providing limits of detection and quenchingconstants when available. This review concludes with a summary ofthe surveyed literature and raises a few concerns that should be addressedin the future development of COP and COF fluorescence-based sensors. Unlike mostelectrostatic bonds, including coordination, hydrogen, and hydrophobicbonds, covalent bonds exhibit high bond strengths and can thus beapplied in the synthesis of chemically more stable and robust materials.It is therefore not surprising that nylon, polyethylene, polystyrene,polyamide, and other products of covalent polymerizations found countlessuses in everyday life.6The ideaof electron pair sharingbetween neighboring atoms, which is central to the definition of acovalent bond, was first introduced by Gilbert N. Lewis in 1916 whenhe presented the Lewis dot structures of covalent compounds.7 Typically, their backbones consist of lightweightelements such as C, H, N, O, F, and S. For specific applications thatrequire metal ions, these can be introduced through coordination bonding.In 2005, these covalent polymeric materials were supplemented by covalentorganic frameworks (COFs).8 The latterare characterized by the presence of dynamic covalent bonds, structurallong-range order, and crystallinity.9 COFsdiffract X-rays, which allows for the precise structure determinationby the modeling of the experimental diffraction patterns. Such periodicityenables experimental and in silico molecular-level investigation ofvarious phenomena, eliminates batch-to-batch variations in cross-linkingdensity, and facilitates precise fine-tuning of the structure by postsyntheticmodification.More recently,insoluble and porous covalent polymers have beenpraised for their extensive surface areas, which can interact favorablywith other molecules through noncovalent interactions, a feature particularlyuseful in the fields of gas separation and storage, pollutant removal,drug delivery, catalysis, energy conversion, and sensing. These materialshave been known under various names, but in the current review weprimarily resort to the term covalent organic polymers (COPs).10 Theseoptical sensors can be based on different transduction mechanisms,including absorption, resonance, and fluorescence.11 Because fluorescence detection is significantly more sensitivethan absorbance and can thus detect lower analyte concentrations,12 there is a push in the literature to designthese kinds of materials for the detection of various analytes.Crystalline COFs and COPs can be designed in sucha way that theextended π-conjugation in their backbone results in useful light-emittingproperties. In comparison with traditional small-molecule chemosensors,these materials are insoluble in water and common organic solvents,which facilitate their separation, regeneration, repeated use, andincorporation into devices. Periodic structures allow introductionof specific target sites to increase the specificity. Furthermore,they possess large surface areas that can interact with targets, andtheir electronic and photophysical properties are tunable. While small-moleculechemosensors may also be noncovalently embedded into various matricesto enhance their stability, these systems may face the issue of leachingthat COPs and COFs avoid on account of their covalent bonding. Allof these properties make COPs and COFs promising sensors for a rangeof analytes, particularly those that interact with highly specializedenvironments such as enantiomers.In this review, we first discuss the physical basis of fluorescenceusing the Jablonski diagram to illustrate the processes of excitationand emission. We also detail the various fluorescence mechanisms thatare found in the existing fluorescence-based COP and COF sensors,including internal charge transfer (ICT), resonance energy transfer(RET), photoinduced electron transfer (PET), and aggregation-inducedemission (AIE). In the next major section of the review, we describethe progress in the synthesis and performance of the relevant fluorescentsensors, primarily discussing the reports covering the past ten years.The synthetic approaches in these reports range from several kindsof C–C and C–N coupling reactions, boronic acid dehydration,azine, hydrazone, imine, imide and amide chemistries to triazine formation.We focus on various analytes, for instance explosives, metal cations,biological molecules, gases, amines, iodine, solvents, volatile organiccompounds (VOCs), enantiomeric compounds, and anions. The currentreview concludes by summarizing the findings obtained herein and providingsome future perspectives on the development of fluorescent COPs andCOFs for sensing applications.13 As a molecule absorbs energy, it is promoted from the groundstate (S0) to the excited state (S1). It isthen subjected to various collisions with surrounding molecules, whichforce it to lose some energy and step down the ladder to the lowestvibrational state of the electronically excited state (S1).14 From there, the molecule returnsto the electronic ground state S0 while emitting energyin the form of light as a fluorescent signal. Fluorescence usuallyoccurs at longer wavelengths (higher frequencies) than the incidentradiation because some energy is lost to the surroundings in the formof nonradiative decay. This observation is known as the Stokes shift.If a molecule contains a moderately heavy atom (which is sometimesthe case in COPs and COFs), such an atom may induce strong spin–orbitcoupling and force the molecule from the excited S1 stateinto the triplet T1 state in a process known as intersystemcrossing (ISC). This state is significantly more stable and the moleculemay remain trapped in it for several seconds or even minutes. However,it is still able to emit light weakly and gradually return to theground state. This phenomenon of light emission is known as phosphorescence,14 but due to its long lifetime it is not generallyused in sensors.The phenomena of fluorescence and other types of radiative decayare commonly explained with the aid of the Jablonski diagram 1.13 As a15 In PET, the electron donor and acceptor form a charge transfercomplex, which relaxes from the excited to the ground state with orwithout emission of a photon. In the former case, a fluorescence signalis observed and the extra electron on the acceptor is returned tothe donor in the last step of the process  is oftenencountered in the literature,18 and itrefers to the same kind of a physical process which occurs specificallyat the Förster radius, a distance between the fluorophoreswhere the energy transfer efficiency is 50%. In ICT, a single fluorophoremust contain both an electron donating and an electron accepting group,such as a phenyl and a triazine ring, respectively. Photoinduced excitationcan increase charge separation in the fluorophore, and subsequentevents depend on the polarity of the solvent. A polar solvent stabilizesthe species with the charges separated. In contrast, in a nonpolarsolvent, the species without charge separation may have the lowestenergy  the intensity decreases which is referred to as turn-off fluorescenceor quenching, (ii) the intensity increases, which is known as turn-onfluorescence or enhancement, or (iii) the maximum intensity shiftsto a different wavelength.22 whichcan occur as a result of diffusive encounter or due to the formation of a complex . These two processes can be distinguished on thebasis of their lifetimes (τ). In static quenching, the fluorescencelifetime remains unchanged if the concentration of the quencher  is increased because any remaining fluorophore moieties,which do not complex with the quencher, retain their original fluorescencelifetime. Thus, τ0/τ = 1. In dynamic quenching,by contrast, increasing concentration of the quencher reduces thefluorescence lifetime. This can be explained by the fact that thegreater presence of the analyte increases the chance of a collisionalencounter with the fluorophore. Therefore, τ0/τ= F0/F. Both types ofquenching can be described by Stern–Volmer equations, whichallow for the determination of the quenching constants. For furtherdetails on these constants, the reader is advised to refer to relatedreviews.25 These types of quenching as well as other mechanismsof fluorescence are further illustrated by specific examples in thenext major section of the review.The fluorescence quenching is a widelystudied theory in the literature,The materials discussed hereinhave been divided into groups bythe type of the analyte they can detect. Within each group, materialsare compared to each other by several metrics, including the limitsof detection  and Stern–Volmerquenching constants, where applicable. The materials are also evaluatedand compared among each other in terms of their selectivity and recyclability.26 Therefore, it is instrumental to design materials,which can detect the presence of these potentially dangerous metalsin drinking water, food, and the environment. In this subsection,we comprehensively review fluorescence COPs and COFs for the detectionof Hg2+, Fe3+, Cu2+, Cr3+, and a few mixed metal cation sensors. A typical mechanism involvedin these types of sensors is an electron transfer from the excitedmaterial to the partially filled d-orbitals of the metal cations throughthe PET mechanism. Regardless of the metal, the strategy of havingpredesigned metal chelation sites in the structure almost always resultsin higher specificity and lower LODs.Numerous heavy metals are naturally presentin the Earth’scrust, and many of them  are required for the proper functioning of the human body.However, excess ingestion of these metals can have negative effectson human health. In addition, certain other metals, such as Hg, Cd,Pb, As, and Ag, are toxic to humans in even minute concentrations.–1, or ≈10 nM. Hg2+ ions are known to have an affinity for S-containing groups.27 While Hg2+ sensors without thesemoieties have also been reported, it is primarily those with freethiol, thioether, and carboxyhydrazide groups that reach lower detectionlimits and greater selectivity  into a covalent polymer.28 The BODIPY dye is nonfluorescent in the originalstate on account of a rapid C=N isomerization that is perturbedwhen Hg2+ forms a coordination bond with two neighboringdye moieties. The initially non-emissive material starts to emit lightin the presence of the metal cations; however, the detection limitfor Hg2+ is rather high at 0.37 μM.Mercuryis a highly toxic metal, which is knownto cause mercury poisoning and can even lead to the deadly Minamatadisease. Thus, the maximum allowed concentration in drinking wateris 2 ppb, 2 μg Lectivity 1. For ex29 The COFexhibited a strong fluorescence signal upon excitation at 390 nm,which was quenched by the addition of Hg2+ ions in acetonitrile.The COF possessed good selectivity as it preferentially removed Hg2+ even in the presence of 2 equiv of various competitive metalions. The LOD was 25 ppb. A similar LOD (22.8 ppb) was also observedfor a triarylamine-based COP synthesized through Suzuki coupling andpostsynthetically modified with thiosemicarbazone to introduce Hg2+ chelation sites.30The very first manuscripton fluorescent COFs for metal ion detectionwas published by Wang et al. in 2016, and it triggered the developmentof diverse COF-based detection systems. In this work, the authorsconstructed COF-LZU8 with thioether functionalities on the startinghydrazide, which produced a polymeric structure with thioethers pointingboth toward and away from the pore interior 3a.29 The2+ binding, a feature integral toreuse of the sensor, was not considered in COF-LZU8 , selectivity forHg2+ in the presence of other cations and anions at fivetimes higher concentrations in DMF, and facile regeneration abilitywith Na2S. This work thus represents a monumental stepin the direction of sensitive, reversible Hg2+ COF sensors.The issue of reversibility was also addressedin the TFPPy-CHYDCOF where the thiol chelation sites were replaced by carbohydrazidelinkages.2+ whilesensing in water would be the most relevant in environmental and healthapplications. This is likely due to the interference of highly polarwater molecules in the fluorescence properties of the synthesizedmaterials. Second, all of the discussed examples focus on inorganicHg2+ detection. Although this species is toxic, it is theorganic mercury such as methyl mercury, or [CH3Hg]+, that is even more hazardous. These species are formed whenHg2+ comes into contact with bacteria in water or soil,and its toxicity is particularly problematic due to its bioaccumulation.Therefore, future sensor design should not neglect [CH3Hg]+, although its handling and storage in a laboratorysetting may be challenging.A few aspects of COPs and COFs mercury sensors remain unaddressed.First, organic solvents are used to dissolve Hg3+ in drinking wateris 5.4 μM, or ≈302 ppb. Similar to Hg2+ sensors,Fe3+ sensors also commonly incorporate metal cation chelationsites that lower the LODs.33 For example,Yamamoto cross-coupling produced a series of COPs (COP6–9)with LODs in the mM range. These materials were interesting for theabsorption competition quenching (ACQ) mechanism for Fe3+ sensing.34 In DMF, both the COP and theFe3+ ions absorb light in the 250–400 nm window,so upon excitation the two species compete for the light energy. Forthat reason, the presence of Fe3+ reduces the excitationof the COP and quenches the fluorescence signal. Interestingly, otherdivalent metal cations exhibit smaller absorption spectral overlapwith the COP, so they are less able to quench the fluorescent signal,ultimately leading to selectivity for Fe3+.Iron is an essential elementin various metabolicprocesses, including oxygen uptake into red blood cells and its transfer,and DNA synthesis. However, if present in higher amounts in biologicalorganisms, it can lead to disease, so iron detection is of importance.The maximum allowed concentration of Fe3+ sensors. For instance, -COOH and-SO2Cl functionalities introduced into conjugated COPssynthesized through Yamamoto cross-coupling  have been reported for Fe3+ sensing.36 These modifications resulted in dynamic Stern–Volmer constantsof 8.4 × 104 and 4.3 × 104 M–1, respectively, which is an order of magnitude higher than the parent,nonfunctionalized COP. In another study, Sonogashira–Hagihara37 cross-coupled TPA-COP contained the tridentateSchiff base sites able to selectively coordinate Fe3+ ions.Similar to the Hg2+ turn-on sensor discussed above,28 Fe3+ induces rigidity and suppressesPET from the imine N to the excited moiety, turning on the fluorescence.The authors refer to this phenomenon as chelation-induced turn-onfluorescence.A rangeof chelation sites can be incorporated into polymeric materials tomake more efficient Fe3+ ions.38 XPS studies on the Fe 2p and N 1s orbitals further confirmedthe chelation process. The LOD in this COF is low at 0.17 μM,and the Stern–Volmer quenching constant is KSV = 2.3 × 104 M–1,which is comparable to other COPs, COFs, and MOFs. Importantly, thesevalues were obtained in water rather than in an organic solvent. Therefore,the results of this report may be more applicable to real-life sensingapplications in environmental, food, and health sciences.A particularly innovative report constitutes theBth-Dma COF, thefirst example of a luminescent COF with predesigned O–N–O′chelation site for the detection of metal ions in water. The O–N–O′chelation sites in this hydrazone-linked COF participate in fluorescencequenching upon addition of Fe39 An azine-linkedCOF-JLU3 with a fluorescence half-life of 1.5 ns was utilized forselective detection of Cu2+ in THF.40 The mechanism involved PET from the COF to the d-orbitalsof the Cu2+ ions that coordinated to the framework throughLewis acid–base interactions with the OH side functional groupsand azine linkages. The LOD of this system was 0.31 μM, andthe Stern–Volmer quenching constant was calculated to be 3.8× 104 M–1. In another study, fourtimes lower LOD (0.076 μM) was achieved with imine-linked COPs-DTsensors with the same kind of sensing mechanism.41 Given that the surface areas of the two materials are comparable(456 and 540 m2 g–1), better performanceof COPs-DT might be attributed to the solvent (isopropanol), or thestrength of chelation. Notably, this material exhibited a good levelof selectivity among 16 metal cations tested and could be regeneratedby adding a strong competitive metal chelating agent (EDTA) withoutcompromising the sensitivity. COPs and COFs for sensing Cu2+ in water are yet to be explored in greater detail and so are thosefor sensing copper species with oxidation states other than 2+.Copper is an essential element for the humanbody. Enzymes utilize it in energy generation, neurotransmitter andpigment synthesis, and epigenetic modification. Its hyper-accumulationin biological fluids and tissues can, however, lead to diseases suchas Wilson and Meknes.32 This work is truly remarkablefor several reasons: (1) it utilizes Knoevenagel condensation, a lesser-knownchemistry in the COF synthesis, (2) postsynthetic amidoximation introducesa large number of -OH and -NH2 functional groups into thenetwork, which serve as exclusive binding sites for UO22+ among 21 metal cations tested, and (3) upon excitationat 270 nm in water, the LOD is 6.7 nM, which is well below the WHOcontamination limit for UO22+ in drinking water(63 nM). XPS results show that UO22+ binds tothe N atoms of the NH2 groups and the O atoms . As such, this work presents a COF sensor of thehighest merit: it is operational in water, exhibits high selectivityand LOD below the allowed concentration in water, and demonstratesan innovative synthetic approach. The challenge now lies in scalingup the synthesis of the material and optimizing its production cost.With increasing dependence on nuclear powerplants for the generation of electricity, the issue of radioactivewaste is more significant than ever before. Materials are being developedto detect uranium and its oxides, such as the TFPT-BTAN-AO COF generatedthrough the Knoevenagel condensation and postsynthetically modifiedby amidoximation 3b.32 Thi45 atomic mass,46 and/or metals with filled d-orbitals.47 The utility of these systems depends on their purpose; they mightbe very helpful when the presence of any kind of heavy metal is ofinterest but less so when our interest is in a particular metal ion.In most cases, the materials contain main-chain or side functionalgroups that form different interactions with metal cations dependingon the type of metal. For instance, an azo-linked conjugated COP exhibitedfluorescence quenching when exposed to heavy metals but showed noresponse to light metals such as Na+ and Ca2+. This difference was rationalized by the hard acid nature of Na+, K+, and Ca2+, which leads to a lowaffinity for aromatic systems and azo groups.46Some sensors for heavy metal cations were not specific to a particularmetal such as the ones presented above but rather exhibited selectivitybased on common properties of metal ions, such as valency and/or oxidationnumber,45 This material canbe used as a rather general heavy metal sensor, as it exhibits turn-onfluorescence in the presence of trivalent metal ions  in THF.The 2D COF had strong interlayer π–π stacking interactions,which were loosened in the presence of these trivalent metal ions,enhancing the fluorescence signal. By observing that an analogousporphyrin-based COF with a similar skeleton does not exhibit enhancedfluorescence in the presence of these metals, the authors concludethat the fluorescence phenomenon is a result of aggregation-inducedquenching, which is common in bulk 2D-COF materials. The LODs werefound to be in the low-μM concentration, which is within therange of maximum allowed limits. It is important to note that sometrivalent heavy metals  among those tested induce only a little fluorescenceenhancement.One of the most interesting examples of COFs showing distinctfluorescence responses to different heavy metal ions is the corrole-basedCorMeO–COF.In general, studies aiming at detecting groupsof metal cationsshould be supplemented by an investigation on the response to mixturesof heavy metals. It would be expected that the sensitivity for eachindividual metal would decrease in the presence of other metal ions,but the extent of the reduction would need to be carefully evaluated.48 Diverse chemical reactions have been utilizedfor the synthesis of nitroaromatics sensors, including nitrile trimerizationinto triazines,49 Sonogashira–Hagiharacoupling,51 Yamamoto coupling,53 Suzuki coupling,54 Buchwald–Hartwigcoupling,55 and imine56 and azo bond formations.57For safety reasons, effective sensorsfor explosives are currentlyhigh in demand. It is therefore not surprising that a plethora ofCOPs and COFs sensors were designed for compounds such as picric acidor 2,4,6-trinitrophenol (TNP), 2,4,6-trinitrotoluene (TNT), 2,6-dinitrophenol(DNP), 2,6-dinitrotoluene (DNT), 2-nitrophenol (NP), and 2-nitrotolueneNT; 2.48 Dive58 others are tailoredto specific explosive compounds.53 Nitrophenolscontain a polar hydroxyl group able to form hydrogen bonds that islacking in nitrotoluenes, often leading to selectivity. For instance,the PCPDI triazine framework formed through trimerization of aromaticnitriles of N,N′-di(4-cyanophenyl)-3,4,9,10-tetracarboxylicdiimide was selective for o-NP to a very low levelof 17.2 pM.49 Other explosives, includingDNT, p-NP, m-NP, and NT exhibitednegligent quenching effect. This selectivity was explained by theformation of hydrogen bonds between o-NP, and O-and N-rich PCPDI and the absorption spectra overlap between the two.The hydrogen bonding is also responsible for the ACQ mechanism dominatingthe fluorescence response. Similarly, in a mixture of TNP, NT, DNT, m-DNB, p-DNB, and NP, Yamamoto-coupledconjugated COP-612 showed a strong preference for TNP.52A range of COPs have beenused for detecting nitro explosives,and this section only discusses the highlights of the literature thatexists in the area. While some materials serve as sensors for nitroexplosives in general,2 functionalgroups  the relative positions of HOMO and LUMOand (ii) the electron withdrawing effects of -NOlgroups 4a.53 The62 The fluorescencesignal of Py-azine COF at 522 nm (λex = 470 nm) wasquenched by the addition of up to 70 ppm TNP due to the static quenchingphenomenon. For the same reasons of hydrogen bond formation by nitrophenolsbut not nitrotoluenes, Py-azine COF along with imide-linked TfpBDHCOF,63 and PI-COF64 showed selectivity for TNP. One of the most potent COFs used forthe detection of general nitro explosives is DL-COF , reactive oxygen species ,72 and antibiotics.73 In TpPa-1@LE, the imine linkages were deprotonated, whichgenerated anionic N– centers that couldinteract with methylglyoxal.69 The latterinduced a shift in emission from 476 to 525 nm. The mechanism of fluorescenceinvolved exciplexes (heterodimeric short-lived species generated inthe excited state) that formed when the excited state TpPa-1@LE collidedwith methylglyoxal molecules and charge transfer occurred to forma luminescent intermediate. •OH radicals, in contrast,transfer an electron to the COF-TpMA framework, forming an aggregatethrough π–π stacking and inducing fluorescencequenching.72 The FRET mechanism is involvedin sensing tetracycline with Suzuki-coupled CMP-LS7 and CMP-LS8.73 These materials and tetracycline form π–πinteractions through aromatic rings and hydrogen bonds.As has been noted with other analytes,the structures of COPs andCOFs can be adapted to form favorable interactions with disease markers and the dye-functionalizedTpPa-1 COF as a turn-on fluorescence indicator.COFsensors for biological molecules often take advantage of incorporatingmetal ions that actively participate in the sensing process in variousways. First, the metal centers can act as electron acceptors. A sensorfor levofloxacin used a COF as a solid support system for Eubehavior 4. Secondnt assay 5a.71 Her76 In most cases,the sensors are attached covalently or noncovalently to the DNA strandscomplementary to the target DNA. Because of these complementary strands,the selectivity of these systems is very high, but it cannot be attributedto the COF. Similar to the Eu3+ ions in the antibioticsensing,74 the role of the COF is primarilyto serve as support or anchor point. For example, carboxylic acid-functionalizedpolyfluorenes were conjugated with a specific oligonucleotide andthe thus-obtained system was used as a FRET sensor for specific complementarychains of DNA.17 In the presence of thetarget DNA and a FRET signal enhancer, the PicoGreen dye, quenchingof the signal was observed at 426 nm and a new emission peak appearedat 530 nm. None of these changes were observed in the presence ofnoncomplementary DNA chains. In addition to being a solid support,COFs in DNA sensing can also be the quenchers of the DNA probe’sfluorescence  knownsmall-molecule pH-responsive molecules are integrated into polymericscaffolds, or (ii) specific protonatable chemical functionalitieswithin the framework are utilized.pH sensing is important in biomedical, clinical, environmental,and industrial process control.78 and pyranine, a known photostable ratiometric pH sensingsmall molecule.79 Coumarin COPs exhibiteda decrease in the fluorescence intensity with an increasing pH inthe range from 10 to 13.6. This can be rationalized with the structuresof the coumarin dyes, which contain an imidazole ring. In neutraland near neutral environments, this ring is protonated and the materialexhibits strong fluorescence. As the pH starts to increase in thehighly basic level, the proton is gradually lost and the fluorescencesignal diminishes. Once deprotonated, the imidazole anion is ableto quench the coumarin fluorescence by transferring an electron tothe coumarin through PET. In contrast, pyranine in PyrAPCN has twoexcitation wavelengths (406 and 460 nm) that respond differently tothe changes in pH. With increasing pH levels, the emission of the406 nm excitation increases, whereas that of the 460 nm excitationdecreases. Using the ratio of the emission intensities at the twowavelengths enables more precise determination of pH in the rangeof 5–9 pH units, which is particularly relevant to biologicalenvironments  general VOC sensors, (ii)sensors for specific VOCs, and (iii) water sensors.83 Sbf-TMP@4:2 was probed for the detection of20 different volatile organic solvents, and the emission peak at ∼590nm was quenched in the presence of nitro compounds or enhanced upon the addition of other VOCs . This difference could be explained by therelative positions of the conduction band of Sbf-TMP@4:2 and the LUMOof the analytes. The material’s conduction band is higher thanthe LUMO of the electron-deficient nitro compounds, so electrons flowfrom the COP to the analyte, which causes quenching. In contrast,the LUMOs of the other analytes are higher than the conduction bandof the COP, so the electrons flow in the opposite direction and thefluorescence signal is enhanced  caused red-shifting of theexciplex emission by forming a charge transfer complex, in which electronswere donated by the COF to the VOC.A generalsensor able to distinguish nitro group-containing VOCsfrom other types of VOCs was composed of triazine and spirobifluorenesubunits and was synthesized by simultaneous Friedel–Craftsand Scholl coupling with different ratios of the reacting monomers.enhanced 5. Anothe84 and acetone.85 An acetone sensor TB-TZ-COP phenylacetylene] (PTMSDPA) swells in anorganic solvent such as ethanol as a result of van der Waals interactions.86 When even a small amount of water is added tothe system, ethanol forms a hydrogen bond with water and dissociatesfrom PTMSDPA. This causes deswelling of the material, ultimately leadingto fluorescence quenching. The stronger the ability of the organicsolvent to form hydrogen bonding with water, the more pronounced isthe deswelling-induced quenching effect. In contrast, TzDa COF containsthe triazine and 2,5-dihydroxyterephthalaldehyde subunits, which bothform hydrogen bonding with trace water.87 Once this interaction forms, ICT from the phenyl to the triazinecore is prevented, resulting in the fluorescence quenching at 500nm. Furthermore, the hydroxyl group on the terephthalaldehyde no longerforms a hydrogen bond with the imine bond of the COF but rather witha water molecule, thereby preventing the excited-state intramolecularproton transfer (ESIPT) and causing signal enhancement at 590 nm.Similar behavior was obtained for various organic solvents , with LODs between 0.006and 0.085%.Finally, in addition to sensing organic solvents, some applicationsrequire an efficient sensor for water, for instance the productionof dry solvents needed in organic synthesis. Such sensors have beendeveloped on the basis of a range of principles. For example, poly were in the range of 1.2–3.49, indicating enantioselectivityfor all five tested organic vapors.The second strategy was implementedin two recent reports of COFs.One of them contained 1,1′-bi-2-naphthol (BINOL), which isa frequently used source of chirality in organic synthesis and materialsscience as well as a fluorophore 8b.104 Th105 The cavity of the macrocyclesin the core could accommodate the amino groups of the three testedchiral amino alcohols. Phenylglycinol and phenylalaninol enhancedthe fluorescence emission by forming a crown ether–amino alcoholadduct, which weakened the π–π interactions betweenthe COF layers. In contrast, tryptophanol formed not only the adductwith crown ether groups but also π–π interactionsand hydrogen bonds with the COFs through its indole rings and indoleNH groups, respectively. This led to the quenching of the fluorescencesignal.In the second report bythe same group, two crown ether-based COFs,CCOF17 and CCOF18, synthesized through Knoevenagel condensation wereturned chiral following the reduction of the double bonds in the -C=C–CNlinkages.106 For these reasons, COFs are possibly some of the most promisingtypes of enantiomeric sensors currently available. However, theirdirect utilization for compounds of interest to pharmaceutical andother industries is currently lacking.While enantiomeric sensing is likely one of the mostchallengingkinds of chemical sensing, the tunable nature of COFs has proven particularlybeneficial. The preparation of these sensors is a daunting task thateither requires multiple postsynthetic modifications or a challengingpreparation of the chiral monomers. Nonetheless, the alternativesare few and are based on biological macromolecules that pose additionalchallenges in handling, storing, and utilization.107 While low molecular weight amines, such as ethylamine, are harmfulfor the aquatic environment but only mildly toxic to humans, higherorder amines have been linked to respiratory, neural, and cardiovasculardamage in humans or to cancer. Colorimetric COP sensors for ammoniaand amines have been studied in the past,110 with some sensor materials changing color in response to the chemicalreduction induced by ammonia,109 or asa result of charge transfer interaction between the electron-deficientCOP and the electron-rich amines.110 However,more recently fluorescence-based sensors have been prioritized onaccount of their sensitivity. Fluorescent COPs and COFs can detectamines in three different ways: (i) by reacting with free NH2 groups of the primary amines,111 (ii)by forming hydrogen bonding with hydrogen and/or nitrogen atoms ofthe amine groups,112 or (iii) by acceptingan electron pair directly from the electron-rich amine groups (doping).114Amines are used in numerous industries, includingchemical, dye,pharmaceutical, military, and food industry.111 These reticularly chosen aldehyde groups chemicallyreacted with primary amines through Schiff base formation while thetrifluoroacetyl groups formed zwitterions or hemiaminals with organicamines. As a result, P7 responded differently to different types ofamines: primary alkyl amines blue-shifted the emission from 525 to435 nm, secondary alkyl amines blue-shifted the emission to 475 nm,and aromatic amines quenched the fluorescence at 525 nm. The samebehavior was also observed in mixtures of amine vapors. The lowestLOD was determined for o-toluidine in the ppt range.117 Insuch materials, the intralayer covalent and interlayer noncovalentinteractions restrict rotation and prevent energy dissipation. Theboronate linkages of the COF acted as Lewis acids and NH3 served as a Lewis base in such a way that the addition of NH3 quenched the fluorescence signal upon excitation in toluene.Finally,NHtriazine 9c.113,11118 Depending on whichavenue the sensor is being developed for, it must meet a differentset of requirements. For any kind of biological sensing, the materialswould need to undergo a thorough investigation on biocompatibility,particle size distribution, and membrane permeability, etc. For environmentalmeasurements, fixing the materials into membranes or other kinds ofsupports would need to be attempted. In the current state-of-the-art,basic research has been mostly focused on investigating the mechanismsof amine sensing and has not yet matured into fully fledged sensingplatforms for specific uses. The promising early studies with goodselectivity and reversibility in most sensors, and increasingly fastresponse times, however, indicate a huge potential of these aminesensors.The detection of amines is mainly needed for environmental applications and in the biomedical field (sensinginside the cells).119 HCl induced quenching of the fluorescence signalobserved at 550 nm with the LOD of 2.38 ppb , for instance, is known to interact favorablywith nitrogen centers of organic molecules by reversibly protonatingthem. This means that sensors reported for this gas operate on a similarprinciple as the pH sensors discussed above. An imine-linked COF TATF-COMthat contained triazine subunits in both of its building blocks hasbeen utilized as a chromogenic and fluorescence-based sensor for HCl.2.38 ppb 9. FTIR m2) is also mildly acidic,so its sensingcan operate on a similar principle. A fluorescence-based Polym-H7sensor has been developed to detect CO2 down to 1.3% (v/v)levels.121 This commercially availablepolymer is composed of fluorescein o-acrylate (apH indicator), methyl methacrylate (MMA) and hydroxymethyl methacrylate(HEMA) and can be incorporated into films by spin-coating. If present,CO2 reacts with tetraoctylammonium hydroxide (TONOH) toform anionic bicarbonate and cationic TON+. The fluorescein o-acrylate pH indicator in the polymer exhibits two fluorescencespectra, one for its protonated native state and the other for itsnegatively charged state complexed with TON+. On the basisof the ratio of the two, the concentration of CO2 can bedetermined.Carbon dioxide  corewas found to be an efficient sensor for CrO 104 M–1 10. TheUCl, which responded to strongly basic anions, primarily F–, but also OH–, SO42–, and CO32–.124 The guanidine linker and, specifically, itsprotonation state play a major role in the process of detection. Fluorideanion is small, polarizable, and basic enough to abstract a protonfrom guanidine, which becomes neutral and is now able to transferan electron to the fluorophore aldehyde in the backbone of DATGCl. DFT calculations on the system showed that the abstractionof a guanidine proton increases the HOMO–LUMO energy so thatan electron can be easily transferred to the fluorophore aldehydevia the PET mechanism. Impressively, the LOD for fluoride anions ofthis system is 5 ppb, which is the lowest ever reported for F– in any class of materials.Another strategyof designing anion sensors is to incorporate specificlinkers, such as guanidine that can donate a proton to an anion servingas a Bronsted–Lowry base, into the backbone of the COFs. Palet al. developed a cationic guanidine-based fluorescent sensor, DATG100 Moreover, certain COPs and COFs have extraordinarilyshort response times of as little as 2 s,32 in addition to being insoluble in water and common organic solvents,which makes separation, purification, and recycling far more efficientthan for soluble materials.10In summary, this review discussed the physical basis of fluorescencein covalent polymeric materials and explained how fluorescence spectroscopycan be used to design covalent polymeric sensor materials. It detailedthe sensing properties of COPs and COFs for various analytes, includingheavy metal ions, explosives, biological molecules, pH, solvents andVOCs, iodine, enantiomers, ammonia and amines, gases, and anions.After a thorough analysis, we conclude that the most common mechanismof fluorescence sensing involves PET, in which a photoexcited electronis transferred from the HOMO or LUMO of the donor to the LUMO of theacceptor, either of which can be the fluorophore. In most reports,the fluorescence intensity is quenched by the addition of the analyte,although several cases of turn-on fluorescence have also been reportedand discussed herein. Low LODs for specific analytes in some discussedmaterials demonstrate the potential of these types of materials forsensing applications; for instance, the most sensitive sensor foriodine among all classes of materials is the PCPP COP.The majority of reports utilize sensorsin organic solventsrather than in water. This might be due to better analyte solubilityin organic solvents, better dispersibility in nonaqueous media, orbetter efficiency of the electron transfer. It is, however, beyonddoubt that water is the most common liquid medium in which detectionof pollutants, toxic compounds, and other analytes is of interestin practical applications. Therefore, more emphasis should be placedon designing sensors with efficient operation in aqueous media.A sensor is only efficient if it can beused multipletimes. This ultimately requires developing a procedure for detachingthe target analyte, which does not harm the structure and functionof the materials, so that their selectivity and sensitivity to thetarget are preserved and the sensor can be reused. Currently, manyreported materials have not been tested for regenerability, or partlyor fully lost their detection potency after regeneration. Yet it isessential to explore this aspect of any material considered to bea sensor in real-life applications.45 Alternatively, rapid isomerization may preventfluorescence of the materials, but the addition of the analyte preventssuch isomerization, ultimately turning-on the fluorescence response.28Itis far easier to detect the appearance of a brightsignal against a dark background than to detect the disappearanceof a bright signal. Therefore, emphasis should be placed on developingthe turn-on fluorescence sensors rather than relying primarily onthe turn-off materials. This can be achieved in 2D materials whoseindividual layers are stacked, so no fluorescence is observed, butthe addition of the analyte relieves the aggregation-caused quenching.63The majority ofthe referenced examples detect analytesin suspensions. Few efforts have been made to investigate how theycan be used as sensors in the solid state although this approach canafford very promising results. For instance, when an imide-linkedCOF was tested for nitroaromatics detection in suspension, its fluorescencewas quenched by the analytes. However, when the same material wasused in a solid-state sensor, the addition of TNP enhanced the fluorescencesignal.Finally, COPs and COFs are typically composed of anisotropicparticles of various dimensions, which can interfere with reproducibilityof the observations. Therefore, protocols should be developed to minimizesuch variations among particles by mechanically grinding them, incorporatingthem into membranes, or coating them on solid supports.Inspite of the major advantages of the two classes of materialsas sensors, there are also several areas where improvements are needed.This analysis of the current state-of-the-art in sensingapplicationsdemonstrates that the recent developments and the impressive performanceof COPs and COFs sensors justify their further investigation and optimization.It also shows that, in the majority of cases, research has focusedon understanding the interplay between the materials’ and theanalytes’ structures and their performance in sensorics. Manymechanistic studies and theoretical modeling have also aimed at gaininga thorough understanding of the mechanisms of these fluorescence sensors.What has commonly been overlooked, and where the greatest opportunitiesawait in the future, is tailoring these sensors to very specific applicationsand investigating all of the external factors that may influence thesensor effectiveness. This involves performing various competitionand interference studies, optimizing the physical parameters suchas temperature, pressure, and humidity, etc., and building full sensorsetups.


However, among cellular infiltration, the mixed subtype was correlated with better overall survival time when compared to lymphoplasmacytic and neutrophilic infiltration (p < 0.05). In conclusion, ECT had no effect on VEGF expression, cellular infiltration, or intratumoral collagen levels in dogs with cutaneous SCC at the time of evaluation, suggesting that early and late post-ECT-treatment phases should be considered. Canine cutaneous squamous cell carcinoma (SCC) is the most common type of skin cancer in tropical countries and is generally associated with exposure to solar ultraviolet light. It has a low metastatic rate, and local treatments, such as electrochemotherapy (ECT), promote long-term control or even complete remission. This study aimed to evaluate pre- and post-ECT treatment expression levels of vascular endothelial growth factor (VEGF) and CD31, cellular infiltration, and intratumoral collagen levels in dogs with cutaneous SCC. A prospective nonrandomized clinical study was performed using dogs with spontaneous SCC treated with ECT. Eighteen lesions from 11 dogs were included in the study. The expression levels of VEGF and CD31; cellular infiltration; and intratumoral collagen levels, as determined by Masson’s trichrome staining, were not significantly different from pre-treatment measurements on day 21 ( Squamous cell carcinoma (SCC) is a malignant epidermal keratinocyte tumor of the skin . Its preSimilar to cutaneous SCC in humans, in dogs, it is usually locally invasive with low metastasis occurring late in the course of the disease, mainly to regional lymph nodes ,14,15. DAnatomically, the epidermis is an avascular layer composed of keratinocytes, while the dermis is a fibroblast-rich network of collagen, capillaries, and lymphatic vessels that serve as an entrance for immune cells . The skiThe extracellular matrix (ECM) is a complex microenvironment capable of inhibiting or stimulating cancer cells. Previous studies have shown that associations between chemicals and biological components, such as the blood vessels, ECM, vascular endothelial growth factor (VEGF), stromal cells, and leukocytes, may contribute to the cancer microenvironment ,29,30,31Masson’s trichrome (MT) staining is a low-cost, practical method used for assessing the ECM, which is a major component of the tumor microenvironment. High intratumoral collagen levels have been associated with increased survival time in dogs with low-grade cutaneous mast cell tumors ,32. CompECT is an emerging non-ablative local treatment with cytotoxic and anti-vascular effects . It is rFew studies have evaluated the histopathological features before and after electroporation-based treatment ,40. HistECT also has vascular effects, including blood flow alterations, such as transient hypoperfusion; apoptosis of tumor endothelial cells; and the generation of a hypoxic environment ,43. FurtTo the best of our knowledge, this is the first study to evaluate VEGF expression levels, cellular infiltration, and intratumoral collagen levels in tissue samples after ECT. To investigate the pathways of ECT action, we aimed to evaluate these parameters before (D0) and after (D21) electroporation-based treatment of dogs with cutaneous squamous cell carcinoma to determine whether they change with treatment. This study was performed in accordance with the National and International Recommendations for the Care and Use of Animals   and was This was a prospective, nonrandomized clinical study (2015–2017) using dogs admitted to the Veterinary Teaching Hospital of São Paulo State University and the Veterinary Teaching Hospital of the University of Franca with naturally occurring cutaneous SCCs that were treated with ECT. Eleven dogs were enrolled in the study, of which five had more than one lesion; thus, we investigated 18 lesions in 11 patients. Written consent to perform the treatment was obtained from the owner. The follow-up period was defined as the time from initial enrollment in the study until the last examination of the patient. The minimum follow-up period was 1 month. All dogs enrolled in this study fulfilled the following criteria: histopathologically confirmed diagnosis of SCC, absence of distant metastases, compliance of the owner with follow-up after 21 d, and the owner’s permission to perform biopsies before (D0) and after (D21) ECT treatment. The same patient group was used previously by our team to evaluate other parameters, and all available clinical and histological associations were evaluated previously .Physical examination and biochemical evaluation  were performed, along with thoracic radiography (three-view), abdominal ultrasound, and fine-needle aspiration of regional lymph nodes for tumoral staging according to the World Health Organization guidelines for skin tumors .The electrochemotherapy protocol was based on a previously described technique  using blBiopsies were obtained intratumorally before the first ECT session (D0) and on day 21 (D21) after ECT treatment. Areas with necrosis and macroscopic aspects of inflammation were avoided when selecting the tumor area. All samples were immediately placed in 10% formalin for 24 h, followed by 70% alcohol until the paraffin sections were prepared. Microscopic necrosis was classified as absent, grade I (+), grade II (++), or grade III (+++). MT staining was performed according to the method described by Prophet et al. , in whicwww.proteinatlas.org, accessed on 15 September 2021).Immunohistochemical staining for VEGF and CD31 was performed for all SCC tissues using the original biopsy samples (D0) and the biopsy specimens collected 21 d after the first ECT session (D21), as previously described . ImmunohVEGF staining was classified with a score of 0 to 4, based on cytoplasmic immunostaining, as follows: 0, no staining; 1, 5–25% of cells immunostained; 2, 26%–50% of cells immunostained; 3, 51–75% of cells immunostained; and 4, >75% of cells immunostained. To evaluate CD31 levels, we analyzed five random high-power fields (400×), and the result was expressed as the median of the five fields for each sample.For statistical analysis, we calculated the mean values of the histopathological and immunohistochemical parameters and classified the value for each parameter as “low” if it was less than the median or “high” if it was greater than the median.p values < 0.05, were considered significant.The data are presented as the mean and standard deviation, and descriptive analyses were performed for the qualitative data. Fisher’s exact tests were used for all variables, when comparing groups D0 and D21. Statistical analyses were performed using Prism® 8.1.0  and Mixed-breed dogs (n = 5) were most found to be most commonly affected by SCC, followed by American pit bulls (n = 3), boxers (n = 2), and English pointers (n = 1). All patients had sparse fur and lightly pigmented skin. The mean age of the animals was 7.5 (standard deviation ± 2.29), with females being more common than males (n = 10). The most commonly affected sites were the abdominal region (n = 10), followed by the thoracic (n = 5), axillary (n = 1), preputial (n = 1), and tibial regions (n = 1). Based on the RECIST criteria, on day 21, of the 11 animals that underwent ECT, 45% presented with PR (5/11), 27% with PD (3/11), and 27% with SD (3/11). Of the 18 lesions that were treated, 61% (11/18) presented with PR, 22.2% with PD (4/18), and 16.6% with SD (3/18). The patients that did not present with CR on day 21 underwent another ECT session until CR or referral for surgery after cytoreduction. The number of sessions that each patient underwent ranged from one to three. Five patients needed a surgical procedure after follow-up due to tumoral macroscopic lesions or due to the owner’s request . At the p = 0.1872) or VEGF staining intensity during the evaluated period  with one sample had a score of 1, six lesions had a score of 2, one sample had a score of 3, and seven lesions had a score of 4. There was no significant difference in VEGF scores between D0 and D21 , followed by neutrophilic (n = 5) and lymphoplasmacytic (n = 2) infiltration. On day 21, mixed cellular infiltration was the most common type observed, followed by equal amounts of neutrophilic (n = 4) and lymphoplasmacytic infiltration (n = 4). No significant difference in cellular infiltration was observed between the time points evaluated (p = 0.0127) when compared to lymphoplasmacytic and neutrophilic pattern. No significant difference was detected for overall survival in the necrosis, MT, and VEGF score nor between well and poorly differentiated tumors (p > 0.05) (data not shown). Interestingly, regarding overall survival, the mixed-pattern infiltration was associated with better survival time , moderate in 6/18 (33.3%), and accentuated in 10/18 (55.5%) samples before ECT. After the procedure, a similar distribution was observed in all samples , with no differences observed in the staining of peritumoral connective tissue , may assist in understanding the effect of ECT on angiogenesis. HIF-1 affects transient hypoxia induced by ECT, as well as the tumor microenvironment after hypoxic stress, by inducing the expression of angiogenic factors, such as VEGF ,63,64. According to Spugnini et al. , it is pFurthermore, we observed that most of the SCCs had a mixed pattern of cellular infiltration before the patients underwent ECT. After treatment, this pattern did not change in a late response (on day 21). This finding is in contrast to the findings of Spugnini et al. , who obsAlthough the incidence of cSCC in dogs is quite high in some countries, little is known about the inflammatory response in skin tumors, as most studies have focused on mammary tumors in dogs ,26. The Previous studies have evaluated the inflammatory cell infiltration induced by ECT . In a stIn another study on women with cutaneous melanoma metastasis, immunohistochemical analysis showed a striking prevalence of CD3+ T lymphocytes at all stages of tissue reaction after ECT. No CD20+ B cells were detected, but the infiltrate consisted largely of CD8+ cells (granzyme-B positive), with few CD4+ lymphocytes. This suggests a persistent immune response of T-cytotoxic lymphocytes, which may explain the long-term local tumor control by ECT. In contrast to the aforementioned studies, we did not observe a significant change in intratumoral cellular infiltration after ECT, with mixed-pattern infiltration being the most common type at both time points. Based on the results of previous studies, we expected a change in the inflammatory pattern, and the absence of an inflammatory component at day 21 post ECT. Instead, a massive inflammatory infiltrate was still present, suggesting that the skin of dogs may have a late-phase response during the course of remission. Another limitation of this study was that no samples were obtained from dogs in complete remission to determine the presence lymphocytic infiltrate, as observed in other studies ,62.Santana et al.  evaluateAlthough we did not perform immunohistochemical analyses to differentiate the subpopulation of leukocytes, lymphocytes were present at both time points, suggesting that either a protective response or tumor development was occurring. Previous studies have reported the presence of lymphocytes associated with tumor inflammatory infiltrates ,69. The combination of ECT plus immunotherapy, represented by immune checkpoint inhibitors, has been evaluated in humans with advanced cancer of the head and neck and non-melanoma skin cancer with potentially beneficial results ,71. ThisOur MT staining results were similar to those of another study showing 11.7% mild, 47% moderate, and 41% accentuated staining in dogs with cutaneous SCC . In contOne of the advantages of using MT staining is its low-cost and practical implementation compared to other techniques. It has been observed that higher intratumoral collagen levels are associated with lower-grade canine cutaneous mast cell tumors, with greater survival times in those with a value lower than 9.25% ,32. In fMT staining was used to evaluate collagen distribution after ECT, with an expectation of increased collagen density. As tumor cells infiltrate the tumor stroma, ECT is expected to induce an antitumor response, a decreased number of neoplastic cells, and the replacement of the tumor cells with collagen. However, we did not observe any of these modifications before or after ECT.Golberg et al.  evaluateFurther research is needed to determine the angiogenic and stromal components in peritumoral and intratumoral areas and correlate these parameters with the response to electroporation-based treatment. Furthermore, we suggest that early and late post-ECT-treatment phases should be evaluated, as no changes were observed on day 21 in our study. In addition, the low number of samples in the present study obtained from clinical practice  limited further conclusions. A larger number of samples, with sequential histological and immunohistochemical analyses, are needed to understand the complexity of the response to ECT. ECT did not change VEGF levels, cellular infiltration, or intratumoral collagen proliferation in dogs with cutaneous SCC at the time point evaluated, suggesting that early and late post-ECT-treatment phases should be evaluated. Moreover, immunohistochemical characterization of the subpopulations of leucocytes should be performed to determine whether the cellular components influence the overall response.


Background: Frailty is a multidimensional concept, including physical, cognitive, social, sensorial, psychological, and nutritional phenotypes. Among these phenotypes, cognitive frailty is the most widely investigated, which is related to many adverse health outcomes in older individuals. Whether cognitive frailty is dynamic or how these frail phenotypes interact remains an open issue. We studied the rate of these changes over time and their associated factors in a 6-year follow-up cohort.Methods: A total of 426 Chinese community-living older adults in Dujiangyan aged 65 years or older were involved and followed up in three visits 6 years apart. Frailty and cognitive function were assessed using the FRAIL scale and the Mini-Mental State Examination scale. Demographic information, geriatric syndrome, and social interaction status were studied. Rates of transitions in cognitive frailty states and associated risk factors were studied. We used the stepwise logistic regression model to analyze risk factors.Results: At baseline, 18.8% of participants were only in the physical frailty (PF) or mild cognitive impairment (MCI) group, and 0.09% of participants were in the cognitive frailty group. By the end of 6 years, 62 (14.5%) participants had died, and the rates of only PF or MCI group and cognitive frailty group increased to 36.2 and 3.3%, respectively. Also, 199 (46.7%) participants had deteriorated compared with the baseline. The multivariate regression analysis showed that older , smoker , poor self-evaluation health status , and malnutrition  were risk factors for worsening, whereas willing to make new friends  was associated with 39% lower chance of deterioration.Conclusion: Cognitive frailty is a dynamically changing state, where transitions may be influenced by multidimensions. Multidimensional monitoring of a wide range of events occurring in aging may be the best way to act early. We hope our study may serve as a starting point for redefining the definition of cognitive frailty by covering different frailty domains. The latest global metrics on life expectancy showed that the populations of older ages are increasing substantially The data were collected from the Survey on the Disease, Psychology and Social Support of the Elderly Community-Dwelling Population in Dujiangyan, which was a prospective cohort study. We collected data using several validated scales of questionnaires, the details regarding the study design have been reported earlier . IncludePhysical frailty at baseline and follow-up visits was evaluated using the FRAIL scale  rather tAccording to the presence of frail and/or cognitive impairment, participants were classified into four groups, namely, (1) normal: no evidence of PF or MCI; (2) only PF or MCI: physically frail older adults with normal cognition or adults with no PF but already exhibiting MCI; (3) cognitive frailty: with the simultaneous presence of PF or MCI; and (4) death. The severity of all the four groups is progressive.Physical function was evaluated using the Instrumental Activity of Daily Living (IADL) Scale including the following items: shopping, cooking, doing housework, financial management, making telephone calls, and taking medication . Disabilt-test or Wilcoxon rank-sum (Mann-Whitney) test for continuous variables, and the chi-square test for categorical variables. We used logistic regression analysis to identify factors associated with the transitions in cognitive frailty and then confirmed their independent contributions with multiple stepwise logistic regression analyses. A two-sided P value of 0.05 was considered statistically significant.Statistical analyses were performed using SPSS Statistics (version 25.0) and EpiData (version 3.1). In this study, data were expressed using either mean ± standard deviation (X ± SD) and median (p25 − p75) for continuous variables or frequencies and percentages for categorical variables. The differences between participants were tested using either unpaired Student’s n = 653) was dominated by female participants  at baseline. The age range was 72.0 , and the percentage of illiteracy was 20.2%. The prevalence of PF, MCI, and cognitive frailty was 6.1, 16.8, and 1.7% at baseline, respectively. In the second survey, we found a higher proportion of poor self-evaluation health status (P = 0.043), malnutrition (P < 0.001), and IADL disability (P < 0.001). In the third survey, MCI and cognitive frailty participants showed a growing prevalence with age . We also found a higher proportion of smoking (P < 0.001) and depression (P < 0.001) based on the second follow-up, but less interested in participating in community activities (P < 0.001) or making new friends (P = 0.004).By the end of 6 years, a total of 426 Chinese community-dwelling participants completed all three visits. P = 0.018) and the number of people who had died significantly increased  compared with baseline, while the rates of other two states were comparable to the first survey. In the third survey, the number of normal people further decreased , and the number of people who had died further increased . Of note, we observed a significant increase in only PF or MCI state and cognitive frailty state after 6 years. Therefore, we speculate that it will take a relatively long time for transitions from normal to different cognitive frailty states.We investigated the changes in the number of different cognitive frailty states over time. P = 0.011). By the end of 6 years, 199 (46.7%) participants had remained stable, 199 (46.7%) participants had deteriorated, and 28 (6.6%) participants had improved. In the third survey, nearly half of the people in the normal group at baseline had stayed in the same state, whereas more than one-third had worsened into the only PF or MCI group, and a small part had degenerated into cognitive frailty or died. Among the only PF or MCI at baseline, 31.3% of participants recovered into the normal state, whereas one-third worsened into cognitive frailty or died. Among the cognitive frailty, 25% of participants recovered to the normal state, and 50% of participants recovered to only PF or MCI state, but one-fourth of participants had died.P < 0.001), smoker , poor self-evaluation health status , malnutrition , and willing to make new friends .This is the first study to report cognitive frailty transitions among Chinese community-living older adults. The overall prevalence of cognitive frailty in this older population was 1.7%, and it significantly increased after 6 years (to 3.8%). There was a higher proportion of smoking, poor self-evaluation health status, depression, malnutrition, and IADL disability with aging. Meanwhile, we found a majority of participants remained stable or had deteriorated after 6 years, but about 6.6% of participants reverted to a better state. Among the participants who had improvement, 89.3% of the individuals were from the only PF or MCI group at baseline, indicating interventions should focus on the phase of precognitive frailty. Among the participants who became worse, 86.4% of the individuals were from the normal group at baseline, suggesting prevention should focus on healthy elders.P = 0.01), and the result was consistent with another research , which may affect cognition.The research on frailty is ongoing, but no consensus on its definition has yet been reached and lack of uniform assessment instruments. Whether older people with PF are more at risk for developing adverse outcomes if they also suffer from cognitive, social, psychological, and nutritional frailty needs further exploration. In our study, cognitive frailty is a dynamically changing state, in which transitions may be influenced by multidimensions. Older age, smoking, poor self-evaluation health status, and malnutrition were associated with worsening, but willing to make new friends was a protective factor. In other words, different frailty phenotypes may interact with each other, even though the underlying mechanism is not clear now. Therefore, multidimensional monitoring of a wide range of events occurring in aging may be the best way to act early. However, from the perspective of health economics, it is not cost-effective to simultaneously evaluate a series of complicated frailty scales among community-living older adults. As cognitive frailty is a fundamental determinant of the vulnerability of an individual to stressors, it is more economical and effective for screening targeting on it. We hope our study may serve as a starting point for redefining the definition of cognitive frailty by covering different frailty domains. Also, we hope to construct a cognitive frailty predictive model by analyzing the results in the future.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by the Ethics Review Committee of Sichuan University. The patients/participants provided their written informed consent to participate in this study.HT assisted with study design, data analysis, and manuscript writing. HZ and QS helped with the interpretation of results. HQ helped in collecting data. SW led the development of the study concept, secured funding for data collection, and provided critical comments. All authors read and approved the final manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The girls underwent treatment three times per week for 8 weeks (24 treatments). Moxibustion was applied to the RN12, RN6, ST25, ST36, and SP6 acupoints. Physical assessments were BMI, waist-to-hip ratio (WHR), and body fat ratio (BFR). Psychological outcomes were measured using the Rosenberg Self-Esteem Scale (RSE). Data were collected at the beginning of the study (baseline), week 4, and week 8. Of the 54 participants, 46 completed the trial. The difference in mean BMI from baseline between the two groups was 0.097 (p=0.655) at week 4 and −0.794 (p=0.001) at week 8. The mean WHR of the treatment group was significantly reduced compared with baseline, with a −0.011 (p=0.017) and −0.035 (p < 0.001) mean change at weeks 4 and 8, respectively. The mean BFR was slightly reduced  at week 4 compared with baseline in the treatment group. At week 8, it was significantly reduced  from baseline in the treatment group. The mean RSE in the treatment group showed no significant increase from baseline at week 4 , but it improved significantly from baseline at week 8  compared to that in the control group. No obvious adverse effect was reported during this study. Moxibustion using a moxa burner may be an effective and safe intervention for overweight adolescent girls, having both physical and psychological benefits.Among adolescent girls, overweight or obesity has both physical and psychological involvement. We conducted a randomized controlled trial of moxibustion using a moxa burner. Fifty-four eligible girls aged 15–18 years with a body mass index (BMI) greater than 25.3 were enrolled in the study. The girls were randomly allocated to the treatment ( Overweight in adolescents is a major health concern worldwide because it is a strong predictor of high risks of cardiovascular disease, type 2 diabetes, and other health problems , 2. MoreTraditional Chinese medicine (TCM) techniques, including acupuncture, body or auricular acupoint stimulation, and acupoint catgut embedding, have become increasingly widely applied for controlling overweight and obesity. Moxibustion is a thermal stimulation method that employs ignited material applied onto or above the surface of the skin of a patient . It can This clinical trial evaluated the effectiveness of moxibustion on adolescent girls with overweight. We hypothesized that, at the end of the 8-week intervention period, patients in the moxibustion group would exhibit more substantial improvement in both physical and psychological function than would those in the control group.N = 27) or control group (N = 27) using computer-generated numbers. Participants who, during the trial, had catastrophic diseases, wounds on the abdomen, or any signs of acute inflammation, as well as those who were pregnant, were excluded. Moreover, participants who missed more than three consecutive sessions during the 8-week intervention were excluded from the trial. The process of this randomized controlled trial was approved by the Institutional Review Board of the Chang Gung Memorial Foundation (95–1478B).A randomized controlled trial was executed to ascertain the effectiveness of moxibustion among adolescent girls with overweight who were from a nursing school in Northern Taiwan. In total, 54 eligible participants aged from 15 to 18 years were enrolled. The participants all had a body mass index (BMI) greater than 25.3, which is the World Health Organization's (WHO's) definition of overweight. Participants were randomly allocated to the treatment group (zhong wan), RN6 (qi hai), ST25 (tian shu), ST36 (zu san li), and SP6 (san yin jiao) acupoints. The intervention was performed using a moxa burner . Moxibustion was applied to the RN12  supply of moxa burners and material following the study period and were taught how to use them, in return for their participation.The physical and psychological variables were measured at the beginning of the study (baseline), week 4, and week 8. The physical outcomes were changes in the BMI, waist-to-hip ratio (WHR), and body fat ratio (BFR). Data were acquired using a digital medical scale  for BMI measurement and In Body 3.0 for WHR and BFR measurement in the laboratory to avoid measurement bias.The Rosenberg Self-Esteem Scale (RSE) was used to assess the psychological changes in the participants during the intervention . The RSEp < 0.05. Differences in general demographic information between the two groups were measured using the chi-squared test. An independent-sample t-test was performed to compare the BMI, WHR, BFR, and RSE score between the two groups at the beginning of the study. Moreover, generalized estimating equations (GEEs) were used to assess the improvements in the BMI, WHR, BFR, and RSE score at the end of week 4 and week 8.SPSS v.15 for Windows was used for data processing and analysis. A statistically significant change was defined as In total, 54 participants were enrolled in this study. N = 21, 87.5%) than were those in the control group ; however, this result was not statistically significant (p=0.058). Most participants did not take regular food supplements or medicine to lose weight. Heterogeneity was examined, and the result showed no statistical significance (p > 0.05).Questionnaires on diet preference and medicine usage also revealed no differences . ParticiThe physical and psychological evaluation data were analyzed using GEEs and are summarized in p=0.655) at week 4 and −0.794 (p=0.001) at week 8. In summary, after 8 weeks of moxibustion intervention, the treatment group participants' mean BMI score was 0.794 lower than that of the control group participants.At week 4, the BMI of the treatment group was slightly increased compared with that of the control group . The difp=0.017 and −0.035; p < 0.001) in WHR after 4 and 8 weeks' intervention, respectively, from baseline  in BFR from baseline at week 4. However, at week 8, a significant decrease  in BFR from baseline was observed  at week 4. At week 8, the treatment group showed a significant improvement from baseline  than the control group . However, the average BMI in our study participants was more than 30 in both groups , which iThe results of our questionnaires revealed that 35 (76.08%) of the participants had previously attempted to lose weight . Most adAccording to the viewpoint of traditional Chinese medicine, the disease pattern observed in obese adolescents was yang deficiency and qi stagnation. Moxibustion has been used for warming yang and dredging meridians, which is favorably indicated for treating obesity. In addition to moxibustion, acupuncture and acupoint catgut embedding are used to treat adolescents with obesity in Taiwan. However, several adverse effects of these treatments—such as pain, hematoma, and granuloma—have been reported . The safp=0.017) in WHR observed at week 4 (Our results revealed that moxibustion reduced the WHR earlier than the other measures, with a significant reduction (t week 4 . This anin vivo through the vagus-gastric neural pathway [Our findings were broadly consistent with those of other studies on acupuncture or moxibustion , 27. The pathway , 31. Sim pathway . HoweverOther physical variables, such as BMI and BFR, showed no significant decrease until week 8. These results were similar to those of other studies that used acupuncture to treat children with obesity , suggestThe association between overweight or obesity and self-esteem was reported to be tenuous in other studies on Han and other ethnic groups , 34, 35.The moxa burner is a relatively safe device, according to our study. The burner, which has a fine metal mesh at the bottom, allows heat to pass without ashes falling onto the skin. During the 8-week intervention, no adverse effects or burns were reported, probably because this safe moxibustion device was used and its method of use was effectively explained. Although other studies have reported potentially adverse effects from moxibustion, such as allergies, burns, and infections , no partOur study had several limitations. First, the trial was not double blinded because performing sham moxibustion is difficult. To date, no validated double-blinded studies on moxibustion have been reported in the literature. Other studies have performed sham moxibustion by using devices to prevent heat radiating from the moxa burner to the patient's skin . HoweverMoxibustion intervention may help improve some physical and psychological variables of adolescent girls with overweight, including the WHR and BFR, as well as the BMI and RSE score. This simple and safe therapeutic method is worthy of promotion by public health authorities.


Diabetes mellitus is a significant clinical and therapeutic problem because it can lead to serious long-term complications. Its pathogenesis is not fully understood, but there are indications that dysbiosis can play a role in the development of diabetes, or that it appears during the course of the disease. Changes in microbiota composition are observed in both type 1 diabetes (T1D) and type 2 diabetes (T2D) patients. These modifications are associated with pro-inflammation, increased intestinal permeability, endotoxemia, impaired β-cell function and development of insulin resistance. This review summarizes the role of the gut microbiota in healthy individuals and the changes in bacterial composition that can be associated with T1D or T2D. It also presents new developments in diabetes therapy based on influencing the gut microbiota as a promising method to alter the course of diabetes. Moreover, it highlights the lacking data and suggests future directions needed to prove the causal relationship between dysbiosis and diabetes, both T1D and T2D. Diabetes is a group of metabolic diseases characterized by hyperglycemia caused by the direct or indirect deficiency of insulin. Type 1 diabetes (T1D) is an autoimmune disease in which antibodies are produced against various elements of pancreatic β-cells; the islets producing insulin become deteriorated and, eventually, are completely destroyed, which causes a lack of insulin . InadequThe gut microbiota contribute to the proper functioning of human organisms . They cr14 bacteria that settle in the gastrointestinal tract, in which they perform a variety of functions, not all yet fully understood. The “microbiome” is considered as the genome of the whole microbiota. The number of bacterial cells was estimated to be about 10 times higher than the number of human cells [Firmicutes and Bacteroidetes, which are the major groups of bacteria, but also Proteobacteria, Actinobacteria, Fusobacteria and Verrucomicrobia. The microbiota of adults include a wide range of species (about 500–1000) belonging to two main phyla—Firmicutes and Bacteroidetes—which makes the bacterial community in every individual specific and unique [The term “the gut microbiota” refers to more than 10an cells , but nowan cells . The micd unique ,14. Maind unique ,15,16.Bacteroidetes mainly generate acetate and propionate, and Firmicutes produce butyrate [Bifidobacterium, belonging to Actinobacteria, directly produce a great amount of the SCFA acetate, but they also produce lactate, which is metabolized by other bacteria to butyrate [Shigella and entero-hemorrhagic Escherichia coli [Actinobacteria contribute to the maintenance of intestinal barrier homeostasis [The intestinal microbiota contribute to carbohydrate metabolism by hydrolyzing and fermenting polysaccharides delivered with food. As a consequence, monosaccharides and short-chain fatty acids (SCFAs) are produced, which can influence the colon locally, but can also be absorbed by the host into the circulation and influence the metabolism of different organs . SCFAs, butyrate . Speciesbutyrate ,25. SCFAbutyrate . They inbutyrate ,28. Theybutyrate . Moreovehia coli ,30,31,32hia coli ,34,35. Aeostasis .Prevotella copri and Bacteroides vulgatus. In turn, the leading species negatively associated with IR are Butyrivibrio crossotus and Eubacterium siraeum [The gut microbiota are able to synthesize branched-chain amino acids (BCAAs)—leucine, isoleucine and valine . These m siraeum . The inc siraeum ,41.The primary bile acids (Bas) are synthesized from cholesterol in the liver and secreted with bile into the gut lumen. Further, they are metabolized by the microbiota to secondary Bas and mostly reabsorbed into circulation, influencing different host processes . Their mThe gut microbiota play a crucial role in preventing infectious diseases by occupying host niches, which can make the host resistant to colonization by pathogens .The gut microbiota also participate in the proper functions of the immune system, which is a complicated mechanism consisting of a variety of different actions. For instance, they take part in the process of inflammatory cytokine production or stimulate the proliferation of group 3 innate lymphoid cells in the colon ,52. MoreProteobacteria and Actinobacteria are less abundant than Firmicutes and Bacteroidetes [Proteobacteria, especially Enterobacteriaceae, has been found in newborn mice [Proteobacteria species, facultative anaerobes, play a key role in preparing the suitable habitat of the infant gut for colonization by strict anaerobes [Proteobacteria, which are probably directly associated with the reorganization of vagal afferents and microglia activation in the nucleus of the solitary tract [Bacteria belonging to the phyla roidetes . A tempoorn mice . By consnaerobes . Vaughn ry tract . A shortFirmicutes/Bacteroidetes ratio and the instability of the microbiota can be one of the early diagnostic markers of developing autoimmune disorders, such as T1D [Bacteroidetes and Streptococcus mitis, while in healthy controls there was a higher prevalence of the butyrate producers Lactobacillus plantarum and Clostridium clusters IV and XIVa [Bacteroides and controls had a higher level of Prevotella, but after 2 years of treatment with insulin, the gut microbiota of patients and of controls were similar [Roseburia hominis, Alistipes shahii and Bifidobacterium pseudocatenulatum were higher, whereas in controls without T1D, levels of Lactococcus lactis and Streptococcus thermophilus were raised. The control group of children not only had more species common in dairy products, but also their microbiota consisted of more genera associated with the biosynthesis of SCFAs and fermentation. This finding supports the theory of the protective effects of SCFAs in T1D [Firmicutes and the Firmicutes/Bacteroidetes ratio were raised and the levels of Proteobacteria and Bacteroidetes were reduced [Firmicutes and increased amount of Bacteroidetes [The stability, connectivity, abundance and composition of the intestinal microbiota are probably associated with the development of T1D . Severalh as T1D . De Goffand XIVa . Similar similar . The fecs in T1D . Pellegr reduced . Moreoveroidetes . Dissimiroidetes . A shortT1D is defined as a β-cell-mediated pro-inflammatory state, induced by both innate and adaptive immunity . SpecifiDuring early childhood, such processes occur as the development of the immune system, maturation of the gut microbiota and appearance of the first autoantibodies bound to T1D . Among tBifidobacterium, Bacteroides and Ruminococcus can cause mucin degradation and impair the integrity of the mucosal barrier [Firmicutes, leads to appropriate mucin synthesis and enhances tight junctions in the intestine [Dysbiosis, defined as the repetitive or prolonged deviation from optimal microbial homeostasis, can cause the loss of self-tolerance and the spread of effector cells and pro-inflammatory signals in the organism . These p barrier . Intesti barrier . The cli barrier . An adeqntestine ,90. Butyntestine . A butyrntestine , whereasntestine .E. coli LPS improved local immunity, while an intraperitoneal injection of E. coli LPS improved the autoimmune response and decreased the incidence of T1D [The alteration of intestinal microbes can induce the leakage of fatty acids and lipopolysaccharides (LPSs) by destroying the intestinal mucosal barrier. This causes the activation of toll-like receptor 4 (TLR4), which results in metabolic inflammation . TLRs are of T1D ,99. Howee of T1D . It is nFirmicutes and class Clostridia. Moreover, the Bacteroidetes/Firmicutes ratio, as well as the Bacteroidetes-Prevotella/C. coccoides-E. rectal ratio, was positively correlated with plasma glucose concentration. Moreover, the class Betaproteobacteria was increased and positively correlated with reduced glucose tolerance [Faecalibacterium and Roseburia, butyrate producers [Akkermansia muciniphila, which shows mucin-degrading properties and plays an important role in gut barrier functions, and the sulphate-reducing species Desulfovibrio [Lactobacillus species and a decreased amount of five Clostridium species [Akkermansia muciniphila in patients with T2D [Clostridium and Akkermansia muciniphila, in comparison to healthy people [Bacteroidetes and increased level of Firmicutes and Proteobacteria, which results in a higher Firmicutes/Bacteroidetes ratio [Firmicutes/Bacteroidetes ratio was definitely higher in T2D-affected patients with complications of the disease than in individuals without complications [Similarly to T1D, the microbiota in patients with T2D differ from those occurring in healthy individuals . The maiolerance ,100. Qinroducers ,70. Qin fovibrio . Moreovewith T2D . A simily people . Converses ratio . These cications .Bacteroides, Bifidobacterium, Faecalibacterium, Akkermansia and Roseburia, and the genera Fusobacteria, Ruminococcus and Blautia are positively connected with this disease [Firmicutes and Bacteroidetes being the dominant phyla, the composition at genus level is utterly different [The results of various studies differ from one another, but, in general, the genera negatively associated with T2D are  disease . The inc disease . Moreoveifferent . The proBacteroides, belonging to the phylum Bacteroidetes, were negatively associated with T2D in the research [B. intestinalis, Bacteroides sp. 20_3 and B. vulgatus were decreased in T2D-affected patients [B. stercoris was increased [B. acidifaciens and B. uniformis favourably affected the glucose tolerance and IR in diabetic rodents [Bacteroides on glucose metabolism and suggest an explanation for the negative correlation between Bacteroides and T2D.research ,105,106.patients ,107,108.ncreased . In anim rodents ,111. StuRoseburia, Faecalibacterium, Lactobacillus, Ruminococcus and Blautia belong to the phylum Firmicutes. Generally, a decrease in the Roseburia level has been found in T2D-affected patients, in comparison to healthy individuals [R. intestinalis was positively and R. inulinivorans and Roseburia_272 were negatively associated with diabetes [Faecalibacterium were found to be decreased in T2D-affected patients, but, at species level, F.prausnitzii was negatively correlated with the disease [Lactobacillus species are rather positively associated with T2D, for instance L. acidophilus or L. salivarius, but some species, such as L. amylovorus, are negatively associated with diabetes [The genera ividuals ,108,112.diabetes ,108,109. disease . Lactobadiabetes ,114,115.Bifidobacterium, belonging to Actinobacteria, are strongly negatively associated with T2D [Bifidobacterium spp. Improved glucose tolerance in diabetic mice, suggesting a protective role of bifidobacterial in T2D [Species of the genus with T2D ,107,113.l in T2D ,117.A short comparison of these changes in the gut microbiota in individuals with diabetes is presented in The development of T2D is mainly caused by insufficient insulin secretion by β-cells localized in the pancreas and the state called “insulin resistance”, which is the inability of insulin-sensitive tissues to respond to insulin properly . The dysEnterobacter cloacae, a bacterium linked to obesity, or bacteria received from obese donors leads to the increased capacity for energy harvest, weight gain and impaired glucose tolerance [Much of our understanding of the exact role of the intestinal microbiota is based on studies focused on germ-free animals, which are born and kept without any contact with bacteria and can be exposed to specific microbes in the course of the research. Studies have shown that these rodents are resistant to obesity induced by diet ,125, andolerance ,127,128.T2D is characterized by the decreased production of butyrate , one of Moreover, it is suggested that patients who will develop T2D in the future show a reduction in BCAA catabolism, as well as changes in lysophospholipid metabolism and in the BA pool . AdditioSimilar to T1D, T2D is probably associated with LPSs, which trigger the development of inflammation and IR acting through TLR4 ,142. TLRRoseburia_272 and Faecalibacterium prausnitzii is lower in T2D-affected individuals than in healthy ones [Roseburia hominis, belonging to the phylum Firmicutes, can contribute to the induction of genes involved in the promotion of gut barrier functioning and innate immunity, as well as in the promotion of mucosal T-cell expansion and differentiation of T cells [R. hominis promotes and regulates the immune system.The intestinal abundance of thy ones ,154. The T cells . Moreove T cells ,157. HerFaecalibacterium prausnitzii, a representative of the phylum Firmicutes, has been shown to be one of the crucial producers of butyrate [F. prausnitzii has an ability to produce salicylic acid, which has anti-inflammatory properties through the reduction of IL-8 levels [F. prausnitzii can result in positive effects in the treatment of diabetes and its complications [butyrate ,159. It butyrate . It has butyrate ,163,164.butyrate ,161. Mor8 levels . It also8 levels . MAM pro8 levels . It has ications .Akkermansia muciniphila is a bacterium belonging to the phylum Verrucomicrobiota and is responsible for mucin degradation in the gut lining, which, as a result, contributes to the syntropic interactions and stimulation of the metabolite pool in the intestine [A. muciniphila has been shown to exert transcriptional changes manifesting as an increase in the expression of genes connected with immune processes and the metabolism of lipids [ntestine . Moreoventestine ,171. In f lipids ,173.Roseburia hominis, Akkermansia muciniphila and Faecalibacterium prausnitzii [Firmicutes/Bacteroidetes ratio [Prevotella, while a protein-rich diet is related to an increased abundance of Bacteroides [1c and triglyceride levels, decreased body weight and improved levels of fasting and postprandial glucose. Such a diet is associated with a reduced Firmicutes/Bacteroidetes ratio and increased amounts of Clostridium and Bacteroides fragilis, which lead to diminished intestinal inflammation and SCFA levels [Diabetes worsens the quality of life of affected patients, leads to many early and late complications, burdens the health care system by increasing treatment costs and causes prolonged absence from work ; therefousnitzii  was obseusnitzii ,177. A ces ratio ,179. Morteroides . After 1A levels .Prebiotics are fermentable, non-digestible food components that promote the growth of bacteria in the intestine . The mosLactobacillus species are the major probiotics with a glucose-lowering potential [Lactobacillus reuteri enhances the secretion of insulin and incretin, but the effect can be bound with an improvement of β-cell function [Lactobacillus acidophilus La5 and Bifidobacterium lactis Bb12 for 8 weeks at a dose of 300 g/day [Probiotics are live microorganisms, either in the form of food or supplement, which can alter the gut microbiota . Lactobaotential . In peopfunction . Moreovefunction . In pati00 g/day .Synbiotics are a combination of prebiotics and probiotics. Synbiotic supplementation has the potential to decrease the serum concentration of IL-6, TNF-α and hs-CRP, which are risk factors for inflammation-dependent cardiometabolic diseases, such as T2D . In patiBifidobacterium and. Administration of specific prebiotics can prevent the development of high-fat diet-induced diabetes and result in improved glucose tolerance, restored insulin secretion, decreased intestinal endotoxin levels and alleviated inflammatory response [Firmicutes/Bacteroidetes ratio and decreases the level of bacteria producing butyrate [Gluten intake affects the development of T1D via altering the gut microbial composition and the immune response . This efresponse . A deficbutyrate . Moreovebutyrate . These mbutyrate .Lachnospiraceae and Clostridiaceae was increased and the amount of Lactobacillaceae was decreased, which indicates a possible improvement in insulin sensitivity in diabetic patients [Another therapeutic strategy is fecal transplant. Six weeks after the infusion of the gut microbiota from lean donors to male recipients with metabolic syndrome, the levels of butyrate-producing intestinal microbiota and the insulin sensitivity of the recipients were significantly increased . De Groopatients .Although much research about diabetes and the gut microbiota has already been performed, we are still at the beginning of the way to show the exact role of the intestinal microbiota in T1D or T2D. Until now, we have frequently based our theories on studies with rodents, but mouse microbiota differ significantly from those in humans. Moreover, the germ-free animals used in experiments are born and kept without any contact with bacteria, and are exposed to selected microbes during the research process. Retrospective and observational research has been performed that does not exactly allow the analysis of the causal relationship between gut microbiota and diabetes development. We still do not know whether the intestinal microbiota are solely involved in β-cell autoimmunity or can also activate T1D. Verification of this hypothesis will require the performance of longitudinal, interventional and prospective studies with adequate methodology and the use of human stool sample processing. Additionally, standardized and reproducible methods of analyzing genetic material are needed. Furthermore, we do not possess enough evidence to definitively prove that dysbiosis can cause T2D, or whether it just appears during the course of diabetes as a consequence of metabolic changes connected with the disease. Further efforts should be directed to creating such studies, which will allow the demonstration of a causal relationship between the changes in intestinal microbiota and diabetes.It is of great importance to understand the exact mechanisms underlying the diseases of civilization, as their prevalence is still rising. Diabetes is one of the most common metabolic disorders and leads to serious complications and consequences. The gut microbiota is an inseparable part of human beings, and understanding its exact role in the functioning of living organisms is necessary. It is of great importance to prove whether there exists the causal relationship between diabetes development and the gut bacteria. Further research is needed, particularly unified studies that can clearly indicate exactly how the microbiota change and how they influence the host, to make the most of the potential included in the gut microbiota.