Catalase immobilized on nanohybrid materials for electrochemical hydrogen peroxide sensors: A review

The studies of heme protein's electrochemistry play a vital role because it provides vast information about the mechanism of metabolic process and biocatalytic pathway. This vast information helps the development and design of biosensors for various medical and clinical applications. In most heme protein's electrochemistry, the electron transfer is almost impossible between heme protein and the underlying bare electrode. This is because of the prosthetic group buried deeply inside the polypeptide chain. Catalase (CAT) is one such heme protein which belongs to oxidoreductases family with ferriprotoporphyrin IX at its redox centre. CAT present in almost all aerobic living organisms, where it plays a major role by catalyzing disproportionation of H₂O₂ in to oxygen and water without forming free radicals. In order to study the electrochemistry of CAT, it has been immobilized on various substrate modified electrodes. Earlier attempts were made by researchers to immobilize CAT over pretreated glassy carbon electrode, graphite impregnated electrode, polymers, didodecyl-dimethylammonium bromide liquid crystals, protein agrose, silica sol-gels and methyl cellulose. CAT immobilized on various nanomaterials composed of carbon nanotubes (CNTs), metal nanoparticles, clay nanoparticles, metal oxide nanoparticles exhibit a dramatic improvement in the H2O2 reduction. Moreover, CAT immobilized on nanomaterial modified electrodes greatly enhances the electron transfer between heme group of the enzyme and electrode surface. The studies show that this heme protein is highly biocompatible and stable. This review discuss mainly upon the various nanohybrid materials immobilized with CAT and their application in H2O2 sensors.