Amino oxidase amperometric biosensor for polyamines

An improved amino oxidase enzyme electrode has been constructed and applied to the determination of the amount of polyamines present in real samples. The electrode is based on the amperometric detection of H 2 O 2 produced in the enzymatic oxidation of polyamines by amino oxidase. Amino oxidase from soybean seedlings, characterized by an extremely high activity for cadaverine and putrescine, was used. The enzyme was immobilized in an agarose matrix in the presence of glutaraldehyde and bovine serum albumin on the surface of a Pt electrode. Cadaverine, in concentrations between 0.5 and 500 μM, can be quantitatively determined by use of the amino oxidase electrode, the linear calibration range being 0.5–10 μM. The lower detection limit was 0.2 μM and the response time was 15 to 60 s. Putrescine showed similar behaviour. The maximum current response for cadaverine was 5.1 μA/cm 2 , with an apparent Michaelis—Menten constant ( K m ′) of 0.175 mM. The sensor response was stable for more than 32 hours of continuous operation at room temperature and, in the presence of fish or meat homogenates, no change in the signal-to-noise ratio was observed. The long-term stability, pH and temperature response of the biosensor has also been studied.