Institute of Analytical Chemistry, Department of Chemistry, Zhejiang University, Hangzhou 310058, China.
Institute of Analytical Chemistry, Department of Chemistry, Zhejiang University, Hangzhou 310058, China.
Biosens Bioelectron. 2018 May 15;105:129-136. doi: 10.1016/j.bios.2018.01.026. Epub 2018 Jan 31.
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 ((j-j)/j), 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.
3,3',5,5'-四甲基联苯胺（TMB）已被广泛应用于 G-四链体/血红素 DNA 酶（G4zyme）为基础的化学和生化分析中，其氧化产物通常通过电化学或光学方法进行监测，以定量测定与 G4zyme 形成相关的分析物。在此，我们报告了一种基于介孔硅-胶束膜（iSMM）的简单电化学方法，用于测量 G4zyme 检测特定分析物中 TMB，而不是其氧化产物。iSMM 生长在氧化铟锡（ITO）电极上，该电极由高度有序、垂直排列的硅纳米通道和十六烷基三甲基溴化铵组成的圆柱状胶束组成。由于胶束结构在分子电荷和疏水性方面具有筛分和预浓缩能力，因此 iSMM-ITO 电极对中性 TMB 具有选择性响应，而对其氧化产物则没有响应。换句话说，只有 TMB 可以被提取并富集到胶束中，然后在下面的 ITO 电极表面（即胶束/ITO 界面）被氧化，产生放大的阳极电流。由于 TMB 的消耗是由存在特定分析物时形成的 G4zyme 催化的，因此该阳极电流的减少使得可以对该分析物进行定量检测。相对于初始电流的电流变化（(j-j)/j），称为电流衰减比，明显依赖于分析物的浓度。作为概念验证实验，在水溶液中检测了四种物质，即钾阳离子（K）、三磷酸腺苷、凝血酶和核酸，并对预处理后的人血清中的 K 进行了分析。
