An interference-free implantable glucose microbiosensor based on use of a polymeric analyte regulating membrane

An implantable glucose microbiosensor that utilizes an electrodeposited redox polymer/glucose oxidase (GOX) sensing membrane and a highly hydrophilic poly (4-vinyl pyridine-co-acrylic acid) (PVP-PAC) overcoating as an analyte-regulating membrane has been developed. A gold microelectrode was electrodeposited with the redox polymer/GOX composite sensing membrane. Two polymers, a hydrophobic poly (4-vinyl pyridine) (PVP) and a hydrophilic PVP-PAC were investigated as possible analyte-regulating membranes. Each was mounted on the sensing layer via chemical cross-linking with poly(ethylene glycol) diglycidyl ether (PEGDGE). High current sensitivities of approximately 220 nA/mM glucose were obtained in the presence of PVP-PAC. In the case of PVP, much lower sensitivities of approximately 30 nA/mM were observed. However, only the biosensor with PVP-PAC showed excellent selectivity to glucose against interferants like oxygen and ascorbic acid (AA). The dynamic range is from 0 to 30 mM. The response time in amperometric measurements was less than 10 sec. Clinical trials showed good correlation between the readings of the subcutaneously implanted biosensor and blood sugar levels.