An ion-sensitive field-effect transistor (ISFET) glucose sensor with a
new membrane structure is fabricated and its characteristics are eval
uated in continuous measurement of non-diluted serum glucose. This sen
sor chip is composed of two ISFETs and a gold electrode. An albumin-gl
utaraldehyde crosslinked membrane, patterned on one of the ISFET gates
and the gold electrode, contacts an enzyme membrane deposited on the
other gate in edge to edge. Making an electrical connection between th
e gold electrode and two ISFETs, this membrane enables stable sensor r
esponses to be made. This sensor is mounted on a flow cell into which
serum samples and air are alternately fed. The sensor output shows a g
ood linear relationship, up to 300 mg dl-1 glucose, and correlates wel
l with a conventional glucose analyzer. This sensor shows promise as a
key device in the development of portable glucose monitors.