Redox hydrogel-based amperometric bienzyme electrodes for fish freshness monitoring

This work presents the design and optimization of amperometric biosensors f or the determination of biogenic amines (e.g., histamine, putrescine, cadav erine, tyramine, cystamine, agmatine, spermidine), commonly present in food products, and their application for monitoring of freshness in fish sample s. The biosensors were used as the working electrodes of a three-electrode electrochemical cell of wall-jet type, operated at -50 mV vs Ag/AgCl, in a now injection system. Two different bienzyme electrode designs were conside red, one based on the two enzymes [a newly isolated and purified amine oxid ase (AO) and horseradish peroxidase (HRP)] simply adsorbed onto graphite el ectrodes, and one when they were crosslinked to an Os-based redox polymer. The redox hydrogel-based biosensors showed better biosensors characteristic s, i.e., sensitivity of 0.194 A M-1 cm(-2) for putrescine and 0.073 A M-1 c m-2 for histamine, and detection limits (calculated as three times the sign al-to-noise ratio) of 0.17 mu M for putrescine and 0.33 mu M for histamine. The optimized redox hydrogel-based biosensors were evaluated in terms of s tability and selectivity, and were used for the determination of total amin e content in fish samples kept for 10 days in different conditions.