Optical Control of Protein Activity in Live Cells by Plasmon Assisted Light Inactivation

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Abstract Optical tools have unparalleled spatial and temporal precision and have been instrumental to better understand various processes in modern medicine and biology. The parent R35 award focuses on developing tools for optical control of protein activity in live cells, based on pulsed laser heating of plasmonic nanoparticles, and its thermally confined heating to unfold and denature surrounding proteins within a few nanometers of nanoparticle surface. The focus of the parent R35 is two-fold: (1) better understand the laser-nanomaterial interactions including the nanoscale temperature in the proximity of the nanoparticle and biochemical responses of the affected proteins; and (2) developing this new optical tool to manipulate protein activity in live cells with emphasis on G-protein coupled receptors (GPCR), an important and diverse class of membrane receptors that mediate extracellular to intracellular signaling. Our recent studies have revealed that shorter picosecond laser stimulation leads to a significant enhancement of the photoacoustic response for gold nanoparticles coated with a thin shell of silica (Au@SiO2), due to the direct electron-phonon (e-ph) coupling across the gold-silica interface and enhanced interfacial heat transfer at the silica-water interface. We further discovered that the picosecond laser excitation of endothelial-targeted gold nanoparticles (AuNPs) generates a nanoscale mechanical perturbation, or photoacoustic effect, and activates mechanosensitive ion channels (TRPV4, Piezo1) and G-protein coupled receptors in live cells. We would like to further continue these investigations by elucidating the mechanism and building biomedical technologies to remotely control the receptor and cell activities with optical resolution. This proposed supplement requests an integrated two- photon stimulation and imaging system to enable these efforts. The scientific rationale is that shorter femtosecond laser stimulation creates a stronger non-equilibrium than even with picosecond or nanosecond laser stimulation, and generates nanoscale mechanical/acoustic response to optically control receptor and cell activities. Our current ongoing studies would benefit from this integrated stimulation and imaging system, as the currently used lasers can be integrated into the optical pathways of the system and utilize the real-time imaging capability. This proposed supplemental equipment fits the scope of the parent award since it would provide a system to (1) access broader timescales by laser-nanomaterial interactions; (2) provide an optical system to allow real-time stimulation and imaging of cellular activities in its native environment; (3) investigate how the pulsed laser including femtosecond laser can control protein activity and cellular responses. All these efforts require integrated stimulation and imaging. Therefore the requested supplement provides an exciting opportunity to investigate the fundamental mechanism of laser-nanomaterial interactions and build biomedical technologies for optical control of the receptor and cellular activities.