Surface Charge Mapping Based on Scanning Ion Conductance Microscopy

Abstract

Scanning Ion Conductance Microscopy (SICM) is capable of high resolution, non-contact topographic imaging of live biological cells under physiological conditions(1, 2). The technique uses the ion current flowing through a nanopipette as a feedback signal to control the pipette probe over the surface. SICM has successfully been combined with a number of other techniques to study live cells. For example, SICM topographic imaging has been performed simultaneously with both patch clamping(3) and confocal microscopy(4). The integration of a surface charge mapping technique with SICM imaging is currently being developed.The charge mapping technique has successfully been used to detect charge arranged in three-dimensions, such as in cationic and anionic polymer brushes. The next stage is to optimise the detection of two-dimensional charge distributions. The technique has the potential for efficient and reliable characterisation of surface charge throughout a biological membrane. Knowledge of membrane surface charge is important because membrane electrostatics affect the conformation and function of many biomolecules and also play a role in intracellular and intercellular recognition and transport(5).(1) Shevchuk, A. I., Frolenkov, G. I. et al. Angew. Chem. Int. Ed.45, 2212 (2006).(2) Novak, P., Li, C. et al. Nature Methods6, 279 (2009).(3) Korchev, Y. E., Negulyaev, Y. A. et al. Nature Cell Biology2, 616 (2000).(4) Gorelik, J., Shevchuk, A. I. et al. PNAS99, 16018 (2002).(5) Cevc, G. Biochim. Biophys. Acta1031, 311 (1990).