Biosensors based on novel plant peroxidases: a comparative study

Amperometric biosensors for hydrogen peroxide detection have been construct ed using horseradish peroxidase (HRP) and two newly purified peroxidases ex tracted from tobacco (TOP) and sweet potato (SPP). The peroxidases were cro ss-linked to a redox polymer [poly(vinylimidazole) complexed with Os(4,4'di methylbipyridine)(2)Cl] using poly(ethylene glycol) diglycidyl ether as the cross-linker. A comparative study with regard to their bioelectrochemical characteristics showed that, irrespective of peroxidase. the biosensors sen sitivity was strongly influenced by hydrogel composition, curing procedure, film thickness and applied potential. The electrostatic interaction betwee n the cationic redox polymer and the negatively charged peroxidases (TOP an d SPP) enhanced the hydrogen peroxide signal. When operated in a Fl system, the optimized SPP biosensor (48% odor polymer, 23% cross-linker and 29% en zyme, w/w %) displayed the highest sensitivity for H2O2 (3.2 A M(-1)cm(-2)) , a linear range up to 220 muM, a detection limit of 25 nM (calculated as 2 S/N) and a response time of about 2 min. (C) 2000 Elsevier Science Ltd. All rights reserved.