Study and Development of Multilayer Needle-type Enzyme-based Glucose Microsensors

Glucose oxidase (GOD)was covalently coupled to a cellulose acetate (CA)layer, using bovine serum albumin (BSA)and parabenzoquinone (PBQ)linkages, Prior to GOD coupling this CA layer was deposited on the platinum tip of a needle-type sensor and covered with an outer layer of polyurethane (PU). Such microsensors were found to be active, their GOD load reaching 1.6 to 3.0 pg mm-' and their glucose response reaching I to 3 PA M-' mme2, even when the upper limit of their linear range reached IO-30 mM. Due to the multilayer structure and composition of these micro- sensors, small anions such as ascorbate were partially discriminated from neutral molecules such as hydrogen peroxide. When implanted sub- cutaneously in anaesthetized rats, sensor responses correlated correctly with blood glucose concentration but presented sensitivity coejjicients signifi- cantly different to those determined in vitro: a 2 point calibration procedure was found necessary for in vivo experiments.