Evaluation of amperometric glucose biosensors based on co-immobilisation of glucose oxidase with an osmium redox polymer in electrochemically generated polyphenol films

Three types of glucose sensors were prepared by electrochemical deposition of glucose oxidase (GOD), [Os(bpy)2(PVP)10Cl]Cl (Os-polymer) (bpy = 2,2ʹ-bipyridyl, PVP = poly(4-vinylpyridine)) within polyphenol (PPh) films on a platinum electrode. The enzyme and Os-polymer in these reagentless sensors were entrapped in stable and reproducible PPh films grown potentiodynamically by cycling the potential between 0 and + 950 mV at 50 mV/s. The first sensor was prepared by immobilising only GOD in a PPh film and was based on H2O2 detection. The Os-polymer-containing electrodes were prepared by two different procedures. In one type, the Os-polymer and GOD were electrochemically deposited on a Pt surface simultaneously with the PPh film. The other type was a bilayer electrode in which the Os-polymer was first adsorbed on a Pt electrode prior to covering with a GOD/PPh film. The latter electrode exhibited better sensitivity to glucose, less interference from electroactive compounds and very low background noise. The electrochemical behaviour of paracetamol, ascorbic acid and uric acid, which normally interfere with glucose detection, was studied with electrodes similar to the glucose biosensors except that they did not contain GOD. The three compounds showed no interaction with the PPh film, which they permeate, and undergo faradaic reaction at the underlying platinum surface. Paracetamol exhibited the greatest film permeation of the insulating PPh film. The relative response (Iss, modified clectrodeIss, pt) of paracetamol was ca. 85-fold and 9-fold in excess of those of ascorbic acid and uric acid, respectively.