Transfected Single-Cell Imaging by Scanning Electrochemical Optical Microscopy with Shear Force Feedback Regulation

Intermittent contact-scanning electrochemical microscopy (IC-SECM): a new approach for tip positioning and simultaneous imaging of interfacial topography and activity

A new scanning electrochemical microscopy (SECM) tip positioning method that allows surface topography and activity to be resolved simultaneously and independently is presented. The tip, controlled by a piezoelectric positioner operated in closed loop, is oscillated normal to the substrate surface. Changes in the oscillation amplitude, caused by the intermittent contact (IC) of the tip with the substrate surface, are used as a feedback signal to control the tip height. The method is illustrated with amperometric feedback approach curve measurements to inert (insulating) and active (conducting) substrates using 12.5 and 1 microm radii Pt disk electrodes. Imaging of gold bands on a glass substrate demonstrates the capabilities for simultaneous topography and activity mapping. The prospect for using IC methodology more widely with other types of tips is highlighted briefly.

Topographic imaging of convoluted surface of live cells by scanning ion conductance microscopy in a standing approach mode

Scanning ion conductance microscopy (SICM) using a nanopipette as a probe and ionic current as a feedback signal was introduced as a novel technique to study live cells in a physiological environment. To avoid contact between the pipette tip and cells during the conventional lateral scanning mode, we adopted a standing approach (STA) mode in which the probe was moved vertically to first approach and then retracted from the cell surface at each measurement point on an XY plane. The STA mode ensured non-contact imaging of the topography of live cells and for a wide range of uneven substrates (500 x 300 microm to 5 x 5 microm). We also used a field-programmable gate array (FPGA) board to enhance feedback distance regulation. FPGA dramatically increased the feedback speed and decreased the imaging time (450 s per image) with enhanced accuracy and quality of live cell images. To evaluate the potential of the STA mode for SICM, we carried out imaging of a convoluted surface of live cell in various scan ranges and estimated the spatial resolutions of these images.