Direct sensing platinum ultramicrobiosensors for glucose

Miniaturized glucose biosensors were constructed from disk-shaped ultramicroelectrodes (UMEs) (diameter = 10 microns and 25 microns), cylindrical UMEs (diameter = 25 microns), and platinum black modified UMEs. Glucose oxidase (E.C.1.1.3.4) was immobilized by glutaraldehyde cross-linking. All ultramicrobiosensors (UMBs) had response times (100% response) of less than 1 min, and had linear response over the human clinical range for glucose (3-7 mM). Response to glucose was linear over a greater concentration range at cylindrical UMBs, compared to similarly prepared disk-shaped UMBs, typically from 3-20 mM glucose. Thin, electrochemically polymerized films were used to prevent signals due to interfering species. A variety of different films, and electropolymerization conditions were examined. Poly(1,3-diaminobenzene) (1,3-DAB) was found to be the most effective at preventing signals due to interferents. Poly(1,3-DAB) was used to protect the biosensor from fouling. A 25 microns biosensor, with poly(1,3-DAB), was used for the direct measurement of glucose in complex samples.