Immobilized Enzyme Film Glucose Biosensors
In this type of biosensors, the enzyme GOD is adsorbed or entangled in the fibrous membrane of the polymers such as poly(vinyl alcohol) (PVA), PLGA, polypyrrole, and poly(o-phenylenediamine) with a covalent linkage. Fig. 10.5 represents a schematic representation of such biosensor.
Miao et al. performed electropolymerization of nonconductive polymer for fabrication onto a planer screen printed electrode to prepare a glucose biosensor . In this device ferrocene was utilized as a mediator for the amperometric glucose response. Glucose measurement was carried out with potentiostating at a potential of 0.3 V. The device has a linear range up to 25 mM with a fast response time of 100 s and sensitivity of 16.6 nA/mM. In another study, Guanglei et al. developed a new efficient and superior glucose biosensor by immobilizing GOD  with electrospinning into PVA fibrous membrane . Membrane immobilization exhibited a rapid response of 1 s. A higher response current of microampere level to glucose was observed in normal and diabetic levels. The electrospinning technique is superior, convenient, and 100 times more efficient than electropolymerization. Moreover, higher sensitivities and lower detection limits are achieved with enzyme immobilized on gold polypyrrole nanocomposite . This biosensor demonstrates very low detection limit, 2 x 10 6 M, and very high sensitivity,
1.09 mA/M, for glucose with a fast response time less than 10 s. Au-pyrrole biosensors have an excellent operational stability up to 100 assays. Gold-pyrrole biosensors demonstrated higher operational stability relative to electropolymerized and electrospun biosensors.
Figure 10.5 Immobilized enzyme biosensor.