Studying and monitoring ion channel activities of single cells are critical for understanding many cellular processes, and for screening ion-channel targeted drug candidates. The current gold standard for electrophysiological recording of ion channel opening and closing processes is the patch clamp technique developed over the past several decades. Although it has been responsible for many fundamental discoveries, the patch clamp method uses a micropipette pressed tightly onto a cell membrane surface and detects electrical current associated with the ion channel activities, which is difficult to operate, low throughput (one- patch at a time) and often invasive (damage to the cell). The proposed project will develop a novel optical method to measure cellular electrical conductance changes due to the opening and closing of ions channels in the membrane. The method is based on the conversion of an electrical conductance signal into a plasmonic signal that can be imaged optically without using the micropipette. This paradigm shift approach promises non- invasive mapping of ion channel activities on single cells with millisecond temporal and sub-micron spatial resolution. The setup is fully compatible with the conventional optical, fluorescence and surface plasmon resonance imaging techniques, thus allowing for simultaneous application of multiple imaging techniques to the same cell, and providing comprehensive and complementary information on ion channels. Such an imaging technique is expected to lead to new insights into drug-ion channel receptor interactions and a new tool for high throughput ion-channel targeted drug discovery.
The specific aims of the project includes: 1) develop the plasmonic technique for mapping of ion channel activities in living cells;2) establish the value of the plasmonic techniqu for electrophysiological studies using nicotinic acetylcholine receptors as a model system;3) demonstrate multifunctional measurements and validate the plasmonic technique with the patch clamp and fluorescence imaging techniques.
Patch clamp technique is a powerful tool for studying ion channels of cells, but it is difficult to operate, low throughput and often invasive. The present project develops an optical method to measure electrical conductance, making it possible to map ion channel opening and closing activities noninvasively with high spatial and temporal resolution. This unprecedented capability is anticipated to provide new insights into ion channel activities and a new tool for high throughput screening of ion-channel targeted drugs.