World Premier International Research Center-Advanced Institute for Materials Research, Tohoku University, Katahira, Aoba 2-1-1, Sendai 980-8577, Japan.
Proc Natl Acad Sci U S A. 2012 Jul 17;109(29):11540-5. doi: 10.1073/pnas.1203570109. Epub 2012 May 18.
We describe voltage-switching mode scanning electrochemical microscopy (VSM-SECM), in which a single SECM tip electrode was used to acquire high-quality topographical and electrochemical images of living cells simultaneously. This was achieved by switching the applied voltage so as to change the faradaic current from a hindered diffusion feedback signal (for distance control and topographical imaging) to the electrochemical flux measurement of interest. This imaging method is robust, and a single nanoscale SECM electrode, which is simple to produce, is used for both topography and activity measurements. In order to minimize the delay at voltage switching, we used pyrolytic carbon nanoelectrodes with 6.5-100 nm radii that rapidly reached a steady-state current, typically in less than 20 ms for the largest electrodes and faster for smaller electrodes. In addition, these carbon nanoelectrodes are suitable for convoluted cell topography imaging because the RG value (ratio of overall probe diameter to active electrode diameter) is typically in the range of 1.5-3.0. We first evaluated the resolution of constant-current mode topography imaging using carbon nanoelectrodes. Next, we performed VSM-SECM measurements to visualize membrane proteins on A431 cells and to detect neurotransmitters from a PC12 cells. We also combined VSM-SECM with surface confocal microscopy to allow simultaneous fluorescence and topographical imaging. VSM-SECM opens up new opportunities in nanoscale chemical mapping at interfaces, and should find wide application in the physical and biological sciences.
我们描述了电压切换模式扫描电化学显微镜（VSM-SECM），其中单个 SECM 尖端电极用于同时获取活细胞的高质量形貌和电化学图像。这是通过切换施加电压来实现的，从而将法拉第电流从受阻碍的扩散反馈信号（用于距离控制和形貌成像）更改为感兴趣的电化学通量测量。这种成像方法具有鲁棒性，并且使用单个纳米级 SECM 电极即可进行形貌和活性测量，该电极易于制造。为了最小化电压切换时的延迟，我们使用了热解石墨纳米电极，其半径为 6.5-100nm，可迅速达到稳定电流，对于最大的电极而言，通常小于 20ms，对于较小的电极则更快。此外，这些碳纳米电极适合于曲折细胞形貌成像，因为 RG 值（探针总直径与活性电极直径之比）通常在 1.5-3.0 的范围内。我们首先使用碳纳米电极评估了恒流模式形貌成像的分辨率。接下来，我们进行了 VSM-SECM 测量，以可视化 A431 细胞上的膜蛋白，并检测来自 PC12 细胞的神经递质。我们还将 VSM-SECM 与表面共聚焦显微镜结合使用，以允许同时进行荧光和形貌成像。VSM-SECM 在界面处的纳米尺度化学映射方面开辟了新的机会，并且应该在物理和生物科学中得到广泛应用。
