In vitro and in vivo calcification of Nafion membrane used for implantable biosensors

The effect of the biological environment on the perfluorosulfonated ionomer Nafion membrane was investigated. The surface topography and surface composition of thermally annealed Nafion membranes were assessed for up to 4 weeks under both in vitro and in vivo conditions. Nafion membranes kept in culture medium or implanted subcutaneously in rats showed extensive cracking. An analysis of surface composition and a fluorescent dye for Ca/sup 2+/ showed an important deposit of calcium phosphates in the membrane. This deposit caused the membranes to crack. This study indicated that Nafion may not be a suitable material for implantable biosensors unless it is modified to prevent mineralization.