Biological modulation with Si-based nanostructured materials. A) Structure of the protein calmodulin, which chelates four Ca2+ ions and in response exposes binding sites that interface with other proteins. Calcium signals are transduced to a vast array of biological responses through the action of CaM. Adapted with permission.[93] Copyright 2007, Cell Press. B) Selective illumination of SiNW-bearing myofibroblasts cocultured with cardiomyocytes yields calcium fluxes that transmit to adjacent cells through different mechanisms based on cell type. MF to CM communication takes place faster than the time resolution of the imaging, while MF to MF signal transmission is considerably slower. Adapted with permission.[54] Copyright 2019, National Academy of Sciences. C) Illustration of the experimental setup used in stimulating dorsal root ganglion cultures. SiNWs are added to cultured cells and given time to interact with the cells. The system is imaged and stimulated on a confocal microscope, with recording of the membrane potential achieved via a patch clamp apparatus. Adapted with permission.[44] Copyright 2018, Springer Nature. D) Dorsal root ganglion neurons interfaced with SiNWs show a calcium response to illumination, which occurs alongside action potential elicitation. The photonically induced AP (right hand spike in the trace) is comparable to an AP induced from direct current injection (left hand spike). Adapted with permission.[44] Copyright 2018, Springer Nature. E) Planar diode junctions embedded in PDMS mesh enable light-based control of rat forelimb motion. The PDMS conforms to the shape of rat brains, so that multiple areas in the sensorimotor cortex to be stimulated. When the mesh is placed on one hemisphere of the brain, illumination results in the contralateral forelimb being noticeably raised. Adapted with permission.[60] Copyright 2018, Springer Nature. F) Trace of the forelimbs from the rat pictured in panel E, showing that photostimulation induces the left forelimb to be raised. Adapted with permission.[60] Copyright 2018, Springer Nature.