Guest Spkr Professor Julie Gorelik, Professor of Cellular Biophysics, National Heart & Lung Institute,Imperial - ‘New nanoscale technique to study signalling in the cardiomyocyte’

Conventional physiological techniques for cardiac cells have attained important achievements during past decades. However, few of them resolve physiological processes at the nanoscale level in living cells. Scanning ion conductance microscopy (SICM) is a unique imaging technique that uses similar principles to the atomic force microscope, but with a pipette for the probe. The scanning technique enables simultaneous recording of high-resolution topography of cell surfaces, and cell surface fluorescence. The hybrid instrument also functions as a vastly improved patch clamp system (the “smart patch”). The method allows scanning of the surface of living cells noninvasively and enables measurement of cellular activities under more physiological conditions than is possible with other techniques.

Since the activity of various receptors and ion channels is highly organized in space and time , it is essential to correlate intracellur signalling with cell structures and subcellular compartments. We describe and validate scanning ion conductance microscopy combined with conventional methods (FRET, patch-clamp, intercellular recording and optical mapping of impulse propagation ) as a new technique for cardiac cell physiology . Such hybrid technologies revealed i) functional localization of beta –adrenergic receptors; ii) location of ionic currents and membrane potential and iii) dynamics of intercellular impulse propagation in cardiac cells.

In addition, we recently developed a SICM modification permitting to apply quantified positive and negative force at defined positions to the surface of cells. With this method hydrostatic pressure (0.1–150 kPa) is applied through a pipette. To prevent any surface contact, or contamination of the pipette, the distance between the pipette and cell surface is kept constant using ion conductance-based distance feedback, allowing fast and repeated measurements. Here we show that we can probe the local mechanical properties of living cells using increasing pressure, and hence measure the nanomechanical properties of the cell membrane and the underlying cytoskeleton in a variety of cells (cardiomyocytes and vascular endothelial cells) and tissue (cardiac valve and aorta) Because the cell surface can first be imaged without pressure, it is possible to relate the mechanical properties to the local cell topography. This method is well suited to probe the nanomechanical properties and mechanosensitivity of living cells.