A novel biosensor using a biochemo-mechanical gel

The volume change of N-isopropylacrylamide (NIPAAm)/acrylic acid (AA) copolymer gel with immobilized glucose oxidase (GOD) was used to construct a biosensor based on a novel principle. The sensor features autonomous operation without electricity or spectroscopic procedures. It consists of a compartment to incorporate the gel, a flow channel to fill a dye solution, and a polydimethylsiloxane (PDMS) diaphragm which separates the gel and the dye solution. A volume change caused by the enzymatic reaction was converted into the change in a liquid column length using the PDMS diaphragm. For concentrations of mM order, 1 min was enough to distinguish the concentrations. When the measurement time was limited within 10 min, the lower detection limit was 200 μM. Undesirable buffering effect could be minimized by reducing the sample volume to 20 μL.