Fluorescent voltage imaging enables the monitoring of neural activity and connectivity across large networks during <i>in vivo</i> thought processes. Present voltage sensitive probes, which include organic dyes and genetically-encoded fluorescent proteins, have limited stability and photobleach within minutes. Semiconductor nanocrystals offer a number of improved optical properties including stronger two-photon absorption, fast fluorescence time constants, and significantly improved photostability. These materials exhibit a voltage dependence in both the spectral position and intensity of fluorescence; however, the magnitude of these effects for single-component materials (i.e. CdSe) is small. We have developed synthetic methods to improve the voltage sensitivity of these materials to the range required for biological studies through precise tuning of the nanocrystal composition and electronic structure. Through an iterative process of quantum mechanical simulation, chemical synthesis, and optical testing under applied electric fields, we have produced samples with strong fluorescence responses under fields of 100 kV/cm. These measurements enable a more complete understanding of the mechanisms underlying voltage sensitivity in semiconductor nanocrystals and have allowed us to optimize their fluorescence response. We have now begun work incorporating these materials into artificial and mammalian neuronal membranes for direct optical measurements of neuron activity.

Compact voltage sensitive nanocrystals for the imaging of neuron activity

251st National Meeting (2016)

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