Guglielmo Lanzani, Istituto Italiano di Tecnologia Milano

I report a new family of photochromic molecules that allow optical control of cell activation by modulating membrane capacitance. We have designed and synthesized light-sensitive azobenzene compounds that stably partition into the plasma membrane. We characterized their photophysics by a variety of spectroscopy techniques and tested their effects on living cells. In neurons, millisecond pulses of visible light induce a transient hyperpolarization followed by a delayed depolarization that triggers action potential firing. These effects are persistent and can be evoked in vivo for up to 7 days, proving the potential of this approach for the modulation of membrane capacitance in the millisecond timescale, without directly affecting ion channels or local temperature. Based on modeling and experiment, we speculate that the photostimulation mechanism is due to dimer formation within the plasma membrane. The ability to optically control cardiomyocyte contraction and elicit cell motion will also be shown, together with applications as a membrane viscosity probe.

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