No abstract

Silicon-based materials have widespread application as biophysical tools and biomedical devices. Here we introduce a biocompatible and degradable mesostructured form of silicon with multiscale structural and chemical heterogeneities. The material was synthesized using mesoporous silica as a template through a chemical-vapor-deposition process. It has an amorphous atomic structure, an ordered nanowire-based framework, and random submicrometre voids, and shows an average Young’s modulus that is 2–3 orders of magnitude smaller than that of single crystalline silicon. In addition, we used the heterogeneous silicon mesostructures to design a lipid-bilayer-supported bioelectric interface that is remotely controlled and temporally transient, and that permits non-genetic and subcellular optical modulation of the electrophysiology dynamics in single dorsal root ganglia neurons. Our findings suggest that the biomimetic expansion of silicon into heterogeneous and deformable forms can open up opportunities in extracellular biomaterial or bioelectric systems.

Wong RC, Cloherty SL, Ibbotson MR, O'Brien BJ. Intrinsic physiological properties of rat retinal ganglion cells with a comparative analysis. J Neurophysiol 108: -2023, 2012. First published July 11, 2012 doi:10.1152/jn.01091.2011.-Mammalian retina contains 15-20 different retinal ganglion cell (RGC) types, each of which is responsible for encoding different aspects of the visual scene. The encoding is defined by a combination of RGC synaptic inputs, the neurotransmitter systems used, and their intrinsic physiological properties. Each cell's intrinsic properties are defined by its morphology and membrane characteristics, including the complement and localization of the ion channels expressed. In this study, we examined the hypothesis that the intrinsic properties of individual RGC types are conserved among mammalian species. To do so, we measured the intrinsic properties of 16 morphologically defined rat RGC types and compared these data with cat RGC types. Our data demonstrate that in the rat different morphologically defined RGC types have distinct patterns of intrinsic properties. Variation in these properties across cell types was comparable to that found for cat RGC types. When presumed morphological homologs in rat and cat retina were compared directly, some RGC types had very similar properties. The rat A2 cell exhibited patterns of intrinsic properties nearly identical to the cat alpha cell. In contrast, rat D2 cells (ON-OFF directionally selective) had a very different pattern of intrinsic properties than the cat iota cell. Our data suggest that the intrinsic properties of RGCs with similar morphology and suspected visual function may be subject to variation due to the behavioral needs of the species. whole cell patch clamp; action potential; vision THE RETINA has an extraordinary task to perform. It must capture, process, and relay all relevant information about the visual scene within one fixation period (ϳ300 ms) before the eye moves on to another target and the process repeats itself. It manages this task through an array of parallel processing networks, each of which is tuned to extract and represent different features of the visual scene (e.g., form, motion, color) and send that information to the appropriate target nuclei via the axons of retinal ganglion cells (RGCs). As a result, it is now commonly believed that 15-20 different arrays of RGCs exist in mammalian retina (for review, see Berson 2008; Masland 2001), each of which carries a unique set of visual information.The visual information carried by RGCs is determined in at least three ways. First, the dendrites of each RGC type sample from the many different types of bipolar (ϳ11 types) and amacrine (ϳ30 types) cells present in the mammalian retina Second, information is filtered independently by each RGC depending upon the neurotransmitter receptors present. Finally, the intrinsic physiological properties of each RGC type ultimately limit the information they can carry. Prior studies of RGC intrinsic properties have been largely limited to...