Poly(vinylferrocene-co-2-hydroxyethyl methacrylate) mediator as immobilized enzyme membrane for the fabrication of amperometric glucose sensor

A hydrophilic copolymer, poly(vinylferrocene-co-2-hydroxyethyl methacrylate) (poly(VFc-co-HEMA)), was prepared as a polymeric electron-transfer mediator for producing amperometric biosensors. When poly(VFc-co-HEMA) was immobilized on a glassy carbon electrode, a redox current was clearly observed in phosphate-buffered saline (PBS). Immobilization of glucose oxidase (GOx) on a poly(VFc-co-HEMA) membrane was carried out to fabricate glucose sensors under mild conditions; these sensors are fabricated using both glutaraldehyde and 1,6-hexamethylenediamine (HMDA) as crosslinking reagents. In the presence of HMDA, glutaraldehyde formed a chemical bond with both HMDA and GOx, and thus, GOx was effectively immobilized on the poly(VFc-co-HEMA) membrane. The activity of the immobilized GOx was stable and poly(VFc-co-HEMA)-mediated glucose sensors could be operated for more than 168 h even at 37 °C. The response current of glucose was observed in the concentration range of 1.3–22 mM, which include the normal level of human blood glucose, hypoglycemia and hyperglycemia. From these results, we could conclude that the poly(VFc-co-HEMA) membrane is useful as an enzyme-immobilizing carrier matrix for fabricating glucose sensors as well as a polymeric electron-transfer mediator.