Controlled membrane depolarization through photothermal effects of tethered gold nanoparticles

Nanoparticle (NP) bioconjugates have an important role in the development of photothermal (PT) therapy, a promising noninvasive approach wherein the NP acts as a light harvesting antenna to convert light into thermal energy to control cellular function. NP-mediated PT control of cellular membrane potential has gained significant interest in recent years as membrane potential regulates proliferation, migration, action potentials (in neurons), and contraction (in muscle cells). Recently gold nanoparticles (AuNPs) and Au nanorods have been demonstrated to induce action potentials via light-induced thermal activation of membrane tethered NPs. Spherical AuNPs have an efficient plasmonic output and are easily modified to interface with the cell surface. We demonstrate here that 20 nm diameter spherical AuNPs (tethered to the plasma membrane by a cholesterol moiety) transduce incident 532 nm light into proximal membrane heating that induces depolarization of membrane potential. Using these NP bioconjugates, we show the ability to controllably induce action potentials in dorsal root ganglion neurons and to control the membrane potential of rat pheochromocytoma cells. The ability to use light-actuated NP conjugates to control cellular behavior is an emerging research field with implications for neuronal and muscle cell modulation as well as in cancer therapeutics.