A NOVEL AMPEROMETRIC TRANSDUCER DESIGN FOR NEEDLE-TYPE IMPLANTABLE BIOSENSOR APPLICATIONS

A novel transducer design is proposed based on a electrocatalyst for h ydrogen peroxide oxidation (platinum black) electrodeposited on the in ner wall of a stainless steel needle which serves as a working electro de, and an external Ag/AgCl reference/counter electrode. Electropolyme rized 1,3-diaminobenezene (1,3-phenylenediamine) is employed as a prot ective layer for the platinum black as well as an interference elimina ting layer. This configuration uses the Pt electrocatalyst in its most active dispersed form and ensures good mechanical ruggedness and prot ection of the catalytic and biological components. The design also pro vides the possibility to obtain high enzyme loading and hence an exten ded sensor life-time. Two types of glucose sensors were constructed ba sed on this novel design concept. The enzyme (glucose oxidase) was imm obilized either in a hydrophilic gel matrix inside the needle body (i) or cross-linked on the inner needle surface (ii). Cellulose triacetat e, polycarbonate, and Nafion were used as external diffusion control l ayers, which extended the linear range of the sensor response to over 25 mM glucose. These biosensors demonstrated diminished response to in terferences from oxidizable compounds present in body fluids and a lif e time of at least three months.