In 1968 Wolfson et al. published the concept for producing energy inside the body using catalytic electrodes exposed to the body fluid as an electrolyte and utilising naturally occurring fuels such as glucose. Since then, the technology has advanced to enhance the levels of power using enzymes immobilised within three-dimensional bioelectrodes that are nanostructured. Current research in the field of enzymatic fuel cells is directed toward applying electrochemical and nanostructural expertise to increase the energy density, to increase the power density, to increase the operational stability, and to increase the voltage output. Nonetheless, biocompatibility remains the major challenge for increasing the life-time for implanted enzymatic biofuel cells. Here, we discuss the current issues for biocompatibility and suggest directions to enhance the design of biofuel cells so as to increase the life-time of implantation whilst maintaining sufficient performance to provide power for implanted medical devices.

We discuss the perspectives of designing implantable medical devices that have the criterion of being symbiotic. Our starting point was whether the implanted device is intended to have any two-way (“duplex”) communication of energy or materials with the body. Such duplex communication extends the existing concepts of a biomaterial and biocompatibility to include the notion that it is important to consider the intended functional use of the implanted medical device. This demands a biomimetic approach to design functional symbiotic implantable medical devices that can be more efficient in mimicking what is happening at the molecular and cellular levels to create stable interfaces that allow for the unfettered exchanges of molecules between an implanted device and a body. Such a duplex level of communication is considered to be a necessary characteristic of symbiotic implanted medical devices that are designed to function for long periods of time inside the body to restore and assist the function of the body. We illustrate these perspectives with experience gained from implanting functional enzymatic biofuel cells.