Renewable miniature enzyme-based sensing devices

A new approach to the preparation of electrochemical biosensors, based on a mixed Sepharose-carbon paste electrode, is described. The bioelectrode is made from carbon paste which is mixed, during preparation, with a mediator and with Sepharose containing an immobilized enzyme. The immobilized enzymes were glucose oxidase, from Aspargillus niger, and amine oxidase from bovine serum and from soybean seedlings. The Sepharose environment, favourable to the enzyme, and the close proximity of the enzyme redox-mediating and sensing sites, permits the required amount of enzyme to be decreased by two orders of magnitude and allows rapid response to the substrate. Response times as short as 15 s have been measured. The microelectrodes are easily fabricated, and the modified carbon paste can be incorporated in the various sensor configurations (micro, flow, etc.) relevant to clinical analysis.