Electrochemically modulated interferometric scattering microscopy for imaging ion channel activity in live cells

Studying ion channel activity and signalling interactions within cells are key tasks in neuroscience. Electrophysiological activities are typically measured with patch-clamp or voltage-sensitive imaging. Unfortunately, these techniques suffer from a trade-off between single-channel sensitivity and high-throughput detection. Here we introduce a label-free electrochemically modulated interferometric scattering microscope (EM-iSCAT) to measure ion channel activity on live cells at both the whole-cell and single-channel levels. We visualize the cellular responses dynamics to osmotic stimulation and record open–close trajectories of single receptor channels with a frame rate of 1.5 kHz. We also localize and distinguish different types of ion channels, including Na+, K+ and Ca2+, on the cell membrane and monitor spatio-temporal heterogeneous responses between different cells in a network. The high-throughput and single-channel sensitivity of EM-iSCAT microscopy enables the simultaneous monitoring of the activity of individual channels, their localization and clustering in the cellular community. EM-iSCAT has the potential to enable the study of any type of ion channel and, more broadly, cell communication pathways mediated by ion channels. Electrochemical modulation enables iSCAT microscopy to detect the electrical activity of live cells by localizing and identifying different types of ion channels down to the single-channel level and imaging frame rates up to 1.5 kHz.