Thin-film polyamine biosensor: substrate specificity and application to fish freshness determination

A polyamine biosensor was developed by immobilizing putrescine oxidase on micro planar thin-film hydrogen peroxide electrodes. The sensor showed a rapid response to putrescine (90% response: 40 s) and the relationship between putrescine concentration and output current was linear between 0.03 and 3 μM under the optimum reaction conditions (pH 8.0, 30°C). The substrate specificity of the polyamine sensor was determined using a flow-injection analysis system. In addition to the main substrate putrescine, the sensor also converted cadaverine (46%), spermidine (45%), agmatine (13%), 1,6-diaminohexane (3%), 1,7-diaminoheptane (2%) and tyramine (13%, non-enzymatic response). These conversion rates were high compared with those of soluble putrescine oxidase. This is probably due to broadening of the enzyme's active centre during the immobilization procedure. The sensor was applied to fish freshness determination during a fish storage experiment. The sensor response obtained in fish extracts increased with increasing storage time and agreed with liquid chromatographic amine determinations.