Horseradish peroxidase and toluidine blue covalently immobilized leak-free sol-gel composite biosensor for hydrogen peroxide

Abstract The enzyme horseradish peroxidase and the water-soluble mediator toluidine blue were covalently immobilized to 3-aminopropyl trimethoxy silane precursor through glutaraldehyde crosslinker. A rigid ceramic composite electrode was fabricated from this modified silane along with graphite powder, which resulted in an amperometric biosensor for H 2 O 2 . The electrochemical behaviour of the modified biosensor was monitored using cyclic voltammetry in the potential range of 0.2 V to − 0.4 V vs SCE. The biosensor exhibited a stable voltammogram with cathodic peak at − 0.234 V and anodic peak at − 0.172 V, with a formal potential of − 0.203 V. Various factors influencing the performance of the biosensor such as buffer solution, pH, temperature and potential were examined for optimizing the working conditions. The modified biosensor exhibited a good catalytic behaviour for the reduction of H 2 O 2 at a lower potential of − 0.25 V without any barrier from possible interferents. The analytical working range was found to be 0.429 μM to 0.455 mM of H 2 O 2 with a detection limit of 0.171 μM. The fabricated biosensor is robust for long-term usage in addition to the high sensitivity, rapid response and having an advantage of surface renewability by simple mechanical polishing.