Nanoscale Photovoltaic Prosthesis For Inducing Repetitive Action Potential Firing in Nerve Cells

Abstract

The incorporation of synthesized nanoscale functional system into living cells and tissues with minimal adverse side effects holds the promise of untold benefits for both basic biological science and medicine. Here, we consider optical excitation of cells through photovoltaic functional abiotic nanosystem (PV-FAN) designed to modulate the membrane potential and thus impact the opening/closing of naturally occurring voltage gated ion channels [1]. The design of the PV-FANs to achieve repetitive action potential (AP) firing in excitable membrane under cw light excitation is analyzed theoretically. The membrane is modeled using (a) the generic Hodgkin-Huxley description and (b) the Fohlmeister-Miller description of the retinal ganglion cells. We find that repetitive AP firing can be induced if the following two basic features are incorporated into the PV-FANs design. The first is the exponential dependence of the excited state decay rate (kd) of the PV-FANs on the membrane potential. The second and most notable necessary feature is that a PV-FAN must involve a three-state system designed such that the decay from its excited state to the ground state is via an intermediate state whose lifetime (gestation time (tg)) is comparable to the absolute refractory time following an AP firing. The capability of PV-FANs to fire repetitive APs could lead to many paradigm-shifting applications including their potential usage as therapeutic agents for partially restoring vision lost to retinal degeneration. Such PV-FANs can be synthesized using appropriate organic and inorganic material building blocks and this analysis provides guidance and incentive for realizing these. [1] Lu S, Madhukar A (2010) Cellular Prostheses: Functional Abiotic Nanosystems to Probe, Manipulate, and Endow Function in Live Cells. Nanomed. NBM. 6:409–418.