Label-free electrochemical biosensors based on 3,3',5,5'-tetramethylbenzidine responsive isoporous silica-micelle membrane.
3,3',5,5'-Tetramethylbenzidine (TMB) has been frequently used as an indicator in G-quadruplex/hemin DNAzyme (G4zyme)-based chemical and biochemical analysis, and its oxidation products are usually monitored by electrochemical or optical methods to quantify G4zyme formation-related analytes. Herein we report a simple electrochemical approach based on isoporous silica-micelle membrane (iSMM) to measure TMB, instead of its oxidation products, in G4zyme-based detection of specific analytes. The iSMM was grown on the indium tin oxide (ITO) electrode, which was composed of highly ordered, vertically oriented silica nanochannels and cylindrical micelles of cetyltrimethylammonium. The iSMM-ITO electrode was selectively responsive to neutral TMB but not its oxidation products, thanks to the sieving and pre-concentration capacity of micellar structures in terms of molecular charge and lipophilicity. In other words, only TMB could be extracted and enriched into micelles and subsequently oxidized at the underlying ITO electrode surface (namely the micelle/ITO interface), generating an amplified anodic current. Since the depletion of TMB was catalyzed by G4zymes formed in the presence of specific analyte, the decrease of this anodic current enabled the quantitative detection of this analyte. The current variation relative to its initial value ((j0-j)/j0), termed as the current attenuation ratio, showed the obvious dependence on the analyte concentration. As proof-of-concept experiments, four substances, i.e., potassium cation (K+), adenosine triphosphate, thrombin and nucleic acid, were detected in aqueous media and the analysis of K+ in pre-treated human serum was also performed.
['Sun|Qinqin|Q|', 'Yan|Fei|F|', 'Su|Bin|B|']
D000255:Adenosine Triphosphate D001560:Benzidines D015374:Biosensing Techniques D004247:DNA D021881:DNA, Catalytic D055664:Electrochemical Techniques D004566:Electrodes D004867:Equipment Design D054856:G-Quadruplexes D006801:Humans D008567:Membranes, Artificial D008823:Micelles D010084:Oxidation-Reduction D011188:Potassium D012822:Silicon Dioxide D013917:Thrombin D017971:Tin Compounds
Label-free Silica-micelle membrane TMB DNAzyme Electrochemical detection