We have developed totally organic electric patch with built-in enzymatic biofuel cell (BFC) for producing iontophoretic current flowing “on-skin” or “through skin”. The skin patches consist of stretchable enzyme electrodes, elastic conductive resistor, hydrogel sheet, and O₂-permeable medical adhesive tape. We used fructose / O₂ system because the enzymes for oxidation of fructose (fructose dehydrogenese) and reduction of O₂ (bilirubin oxidase) can work without the presence of electron mediators for electrocatalysis, resulting in a simple configuration of the patch. The patch, when mounted on the skin, generates a transdermal ionic current with the osmotic flow from anode to cathode. I will present the results of two applications of the BFC patch. One is the transdermal dosing by the “through skin” current. The other is the wound healing by “on skin” current.

To improve delivery efficiency of skin patch, the iontophoresis induced by mild electric current (below 500 μA cm^-2) has been used. The integration of a lightweight and safe power source would produce a more patient-compliant iontophoresis patch. Herein, we prove the BFC can drive iontophoresis, and realize totally disposable electric DDS patch.

Cells in the skin respond to electric current during a wound healing process. Taking advantage of this phenomenon, a stretchable bioelectric plaster is developed to generate ionic current along the surface of the skin by enzymatic electrochemical reactions. The bioelectric plaster fits to the skin and generates electric current above the wound for 12 hours to accelerate wound healing.

In addition to the above applications of BFC for generating iontophoretic flow, we have studied also the application of BFC for sensing medical information. I will present the results on the sensing of lactic acid in sweat and in interstitial fluid with the self-powered skin patches.

References: “Organic Transdermal Iontophoresis Patch with Built-in Biofuel Cell” Nishizawa et al., Advanced Healthcare Materials, 2015, 4, 506-510. “Accelerated Wound Healing on Skin by Electrical Stimulation with a Bioelectric Plaster” Nishizawa et al., Advanced Healthcare Materials, 2017, 6, 1700465-1700470.