Ma Chaoxiong, Zaino Iii Lawrence P, Bohn Paul W
Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA . Email:
Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , IN 46556 , USA.
Chem Sci. 2015 May 1;6(5):3173-3179. doi: 10.1039/c5sc00433k. Epub 2015 Mar 25.
We present a new configuration for coupling fluorescence microscopy and voltammetry using self-induced redox cycling for ultrasensitive electrochemical measurements. An array of nanopores, each supporting a recessed disk electrode separated by 100 nm in depth from a planar multiscale bipolar top electrode, was fabricated using multilayer deposition, nanosphere lithography, and reactive-ion etching. Self-induced redox cycling was induced on the disk electrode producing ∼30× current amplification, which was independently confirmed by measuring induced electrogenerated chemiluminescence from Ru(bpy)/tri--propylamine on the floating bipolar electrode. In this design, redox cycling occurs between the recessed disk and the top planar portion of a macroscopic thin film bipolar electrode in each nanopore. Electron transfer also occurs on a remote (mm-distance) portion of the planar bipolar electrode to maintain electroneutrality. This couples the electrochemical reactions of the target redox pair in the nanopore array with a reporter, such as a potential-switchable fluorescent indicator, in the cell at the distal end of the bipolar electrode. Oxidation or reduction of reversible analytes on the disk electrodes were accompanied by reduction or oxidation, respectively, on the nanopore portion of the bipolar electrode and then monitored by the accompanying oxidation of dihydroresorufin or reduction of resorufin at the remote end of the bipolar electrode, respectively. In both cases, changes in fluorescence intensity were triggered by the reaction of the target couple on the disk electrode, while recovery was largely governed by diffusion of the fluorescent indicator. Reduction of 1 nM of Ru(NH) on the nanoelectrode array was detected by monitoring the fluorescence intensity of resorufin, demonstrating high sensitivity fluorescence-mediated electrochemical sensing coupled to self-induced redox cycling.
我们展示了一种用于耦合荧光显微镜和伏安法的新配置，该配置使用自诱导氧化还原循环进行超灵敏电化学测量。使用多层沉积、纳米球光刻和反应离子蚀刻制造了一系列纳米孔，每个纳米孔都支撑着一个凹陷的圆盘电极，该电极与平面多尺度双极顶部电极在深度上相隔100 nm。在圆盘电极上诱导自诱导氧化还原循环，产生约30倍的电流放大，这通过测量浮动双极电极上Ru(bpy)/三丙胺诱导的电化学发光得到独立证实。在这种设计中，氧化还原循环发生在每个纳米孔中凹陷的圆盘与宏观薄膜双极电极的顶部平面部分之间。电子转移也发生在平面双极电极的远程（毫米距离）部分以维持电中性。这将纳米孔阵列中目标氧化还原对的电化学反应与双极电极远端细胞中的报告分子（如电位可切换荧光指示剂）耦合起来。圆盘电极上可逆分析物的氧化或还原分别伴随着双极电极纳米孔部分的还原或氧化，然后分别通过双极电极远端二氢试卤灵的氧化或试卤灵的还原进行监测。在这两种情况下，荧光强度的变化由圆盘电极上目标对的反应触发，而恢复主要由荧光指示剂的扩散控制。通过监测试卤灵的荧光强度检测到纳米电极阵列上1 nM的Ru(NH)的还原，证明了与自诱导氧化还原循环耦合的高灵敏度荧光介导电化学传感。
