NEW MICROMINIATURIZED GLUCOSE SENSORS USING COVALENT IMMOBILIZATION TECHNIQUES

Glucose monitoring is at present the most widespread application of the GOD/H2O2 system. This paper deals with a new technique for immobilizing onto electrochemical thin-film electrode cells based on this detection principle. The thin-film structure consists of a 100 nm thick titanium-platinum or -palladium sandwich layer on glass substrates isolated by a 3 μm silicon nitride film. A three-electrode miniaturized electrochemical cell with an outer diameter of 200 μm was produced by means of standard wet and dry etching procedures. The Ag/AgCl reference electrode was produced by depositing and structuring a 1 μm thick silver film which was subsequently chlorinated by FeCl3. The Pt or Pd surface was oxidized electrochemically in dilute aqueous oxidizing solutions. The modified surface was derivatized with amino-organic silylating agents. The covalent coupling of glucose oxidase was carried out by introducing a substituted bifunctional 1,4-benzoquinone group between the silylated electrode surface and the enzyme. A sulfonated polymer was used to protect the enzyme layer and to modify the diffusion characteristics of the electrode. © 1990.