Nanoparticles and modified fluorescent proteins for imaging of transmembrane potential

Visual monitoring of membrane potential would be extremely useful for monitoring cell health and activity in any cultured neuron system. On long time scales, cell health in response to depolarization and/or hyperpolarization would be able to be quantified. If the reporter has sufficient time resolution, action potentials may be resolved, thus allowing for optical recordings from ensembles of neurons without growing cultures on multielectrode arrays. However, the creation of such probes is extremely challenging. Here we present preliminary results for two genetically-encoded systems: one based upon fluorescence resonance energy transfer (FRET) between nanoparticles and an engineered channel, and the second based upon fluorescence complementation (FC). The results suggest that chronic monitoring of neuronal potential is possible with these probes, at least on the scale of hundreds of milliseconds.