Interferent Suppression Using a Novel Polypyrrole-Containing Hydrogel in Amperometric Enzyme Biosensors

Amperometric biosensors for three clinically important analytes; glucose, cholesterol and galactose were prepared using a novel polymer composite material consisting of a poly(hydroxyethylmethacrylate) [p(HEMA)] hydrogel intimately combined with polypyrrole (PPy), the appropriate enzyme and fabricated on platinum electrodes. These biosensors were evaluated for their sensitivity to two very common electrooxidizable interferents, ascorbic acid and L-cysteine. The composite polymer films showed effective suppression of these interferents in a serum matrix with a deviation of <5% of the biosensor response being observed at ascorbic acid and L-cysteine concentrations that were twice as high as the normal physiological levels found in serum (10 mg L−1 and 4 mg L−1 respectively). In contrast, biosensor films containing an external layer of peroxidase or Nafion were found to be less effective than the p(HEMA)/PPy composite films in screening these two interferents. The sieving properties of the crosslinked hydrogel and the anion exchange properties of the cationic polypyrrole together with its “dopant” anion effectively inhibit transport of these anion interferents to the electrode.