Smart-Patch Technique

When a patch pipette approaches a cellular surface at distances comparable to the size of the tip opening, the monitored pipette current drops before the pipette touches the membrane. Fine nano-tipped glass electrodes can effectively function as “spherical sensors” that can “roll” over surface irregularities in the specimen without damaging it. By keeping the pipette current constant (so the distance between the pipette tip and the sample surface remains constant) and scanning the sample, it is possible to obtain an image of its surface without physical contact between the pipette and the surface. Thus, one can first image the cellular surface using fine-tipped patch pipettes with scanning ion conductance microscopy (SICM) methodology and then position the same pipette precisely at locations of interest (e.g., scallop crests, T-tubules in cardiac myocytes, neuronal dendrites); finally, a giga-ohm seal can be formed according to the conventional patch-clamp procedure. This smart combination of patch-clamp and SICM methods is called the smart-patch technique. It allows precise mapping of ion channels over the cellular surface.