A BIOSENSOR FOR L-AMINO-ACIDS USING POLYTYRAMINE FOR ENZYME IMMOBILIZATION

Electrodeposition of polytyramine is demonstrated to be a simple and convenient procedure for electrode modification, generating amine groups to which L-amino acid oxidase can be covalently bound. An L-amino acid oxidase (L-AAOD)-polytyramine electrode can be used for detection of L-amino acids, via the current due to oxidation of enzymatically produced hydrogen peroxide. The calibration graph of the sensor for phenylalanine is linear up to 1.4 mM with a lower limit of detection of 0.07 mM. The useful measuring range for leucine is between 0.07 and 3 mM. The enzyme-polytyramine electrodes are stable for more than 1 month. The polymer coating affords some protection of the electrode from direct (nonenzymic) oxidation of electroactive amino acids, which may otherwise cause electrode fouling, although at present, the polymer selectivity is insufficient to prevent errors in estimation of analyte concentration.