Calcium‐dependent modulation of BK _Ca channel activity induced by plasmonic gold nanoparticles in pulmonary artery smooth muscle cells and hippocampal neurons

Gold nanoparticles are widely used for biomedical applications, but the precise molecular mechanism of their interaction with cellular structures is still unclear. Assuming that intracellular calcium fluctuations associated with surface plasmon-induced calcium entry could modulate the activity of potassium channels, we studied the effect of 5 nm gold nanoparticles on calcium-dependent potassium channels and associated calcium signaling in freshly isolated rat pulmonary artery smooth muscle cells and cultured hippocampal neurons.Outward potassium currents were recorded using patch-clamp techniques. Changes in intracellular calcium concentration were measured using the high affinity Ca2+ fluorescent indicator fluo-3 and laser confocal microscope.In pulmonary artery smooth muscle cells, plasmonic gold nanoparticles increased the amplitude of currents via large-conductance Ca2+ -activated potassium channels, which was potentiated by green laser irradiation near plasmon resonance wavelength (532 nm). Buffering of intracellular free calcium with ethylene glycol-bis-N,N,N',N'-tetraacetic acid (EGTA) abolished these effects. Furthermore, using confocal laser microscopy it was found that application of gold nanoparticles caused oscillations of intracellular calcium concentration that were decreasing in amplitude with time. In cultured hippocampal neurons gold nanoparticles inhibited the effect of EGTA slowing down the decline of the BKCa current while partially restoring the amplitude of the slow after hyperpolarizing currents.We conclude that fluctuations in intracellular calcium can modulate plasmonic gold nanoparticles-induced gating of BKCa channels in smooth muscle cells and neurons through an indirect mechanism, probably involving the interaction of plasmon resonance with calcium-permeable ion channels, which leads to a change in intracellular calcium level.