Miniaturized glucose biosensors were constructed by all-chemical means
from disk-shaped carbon ultramicroelectrodes (UMEs) (diameter = 8 mum
). These ultramicrobiosensors (UMBs) are capable of direct measurement
of glucose in the presence of interfering species. Carbon UMEs were p
artially platinized by the electrochemical reduction of a platinum (IV
) complex. Platinization of the carbon UMEs gave an increased current
response to hydrogen peroxide and allowed the modified electrode to be
operated at a lower oxidative potential. Glucose oxidase (E.C. 1.1.3.
4.) was immobilized either by glutaraldehyde cross-linking or by direc
t covalent attachment to the electrode surface using carbodiimide. Res
ponse time (100% response) was 15-45 seconds. Response was linear over
the range of 3-7 mM glucose. An electropolymerized film of poly(1,3-d
iaminobenzene) was used to prevent interfering species.