A Self-Cleaning Membrane to Extend the Lifetime of an Implanted Glucose Biosensor

摘要

The lifetime and efficacy of a subcutaneously implanted glucose biosensor could be greatly improved by a self-cleaning membrane capable of periodic physical removal of adhered cells associated with the foreign body reaction. Previously, we reported thermoresponsive double network nanocomposite (DNNC) membrane comprised of poly(N-isopropylacrylamide) (PNIPAAm) and embedded polysiloxane nanoparticles. When the membrane was thermally cycled above and below its volume phase transition temperature (VPTT, ~33–35 °C), the associated deswelling and reswelling, respectively, led to in vitro cell release. Herein, this membrane design was tailored to meet the specific demands of a subcutaneously implanted glucose biosensor and critical functional properties were assessed. First, N-vinylpyrrolidone (NVP) comonomer increased the VPTT to ~38 °C so that the membrane would be swollen and thus more permeable to glucose in the “off-state” (i.e. no heating) while residing in the subcutaneous tissue (~35 °C). Second, glucose diffusion kinetics though the DNNC membrane was experimentally measured in its deswollen and reswollen states. A cylindrical DNNC membrane with dimensions considered suitable for implantation (1.5×5 mm, diameter × length) was used to model the glucose diffusion lag time. In addition, the DNNC cylinder was used to observe dimensional changes associated with deswelling and reswelling. Non-cytotoxicity was confirmed and self-cleaning was assessed in vitro in terms of thermally-driven cell release to confirm the potential of the DNNC membrane to control biofouling.