Single live cell topography and activity imaging with the shear-force-based constant-distance scanning...

In recent years, scanning electrochemical microscopy (SECM) has become an important tool in topography and activity studies on single live cells. The used analytical probes ("SECM tips") are voltammetric micro- or nanoelectrodes. The tips may be tracked across a live cell in constant-height or constant-distance mode, while kept at potentials that enable tracing of the spatiotemporal dynamics of functional chemical species in the immediate environment. Depending on the type of single live cells studied, cellular processes addressable by SECM range from the membrane transport of metabolites to the stimulated release of hormones and neurotransmitters and processes such as cell respiration or cell death and differentiation. In this chapter, we provide the key practical details of the constant-distance mode of SECM, explaining the establishment, and operation of the tailored distance control unit that maintains a stable tip-to-cell separation during scanning. The continuously maintained tip positioning of the system takes advantage of the decreasing impact of very short-range hydrodynamic tip-to-surface shear-forces on the vibrational amplitude of an oscillating SECM tip, as the input for a computer-controlled feedback loop regulation. Suitable microelectrode probes that are nondestructive to soft cells are a prerequisite for the success of this methodology and their fabrication and successful application are the other topics covered.