High-Resolution Imaging of Nanostructured Si/SiO2 Substrates and Cell Monolayers Using Scanning Electrochemical Microscopy

High-resolution scanning electrochemical microscopy (SECM) in the constant-height mode was applied to image details of a nanostructured porous substrate as well as a confluent epithelial cell monolayer. Platinum disk ultramicroelectrodes (UMEs) with radii down to 100 nm were fabricated by sealing electrochemically etched Pt wires into soda-lime glass capillaries. A subsequent thermal treatment was used to improve the quality of electrode sealing. The size and shape of the SECM probes were adapted to the requirements of the inorganic and biological surfaces to enable high-resolution SECM imaging and to ensure stability and reliability during image acquisition. A mesoporous substrate (Si/SiO2) with 800 nm rectangular pores was imaged with sub-mm resolution. In addition, confluent epithelial cell monolayers derived from kidney were investigated. Independent measurements with ferrocene methanol and hexamine ruthenium (III) chloride led to equivalent SECM results. High quality SECM images with well separated cells within the monolayer were obtained. Resolved regions of cell-cell contacts extending about 1-3 mu m in lateral direction were imaged.