Electrocatalysis By Heme Proteins and Human Liver Microsomes Bound to Magnetic Nanoparticles and Immobilized on Electrodes

Abstract

To develop bioelectrodes with high catalytic efficiency in a minimal reactor volume, elegant tailoring of remarkable enzyme catalysts with nanomaterials is promising. In particular, the role of magnetic nanoparticles (MNPs) in enzyme electrocatalysis and electrochemical biosensors has received notable attention recently. Biomolecules bound to magnetic nanomaterials allow easy isolation from the bulk solution involving simple application of a magnetic field. In this study, we designed a biocatalytic system made of peroxidase-like myoglobin, as a model protein, to covalently conjugate with carboxylic acid functionalized MNPs to examine the catalytic stability, scalability, and reusability features of this bioconjugate. Application of the conjugate was effective for electrochemical reduction of organic and inorganic peroxides, and for both peroxide-mediated and electrocatalytic oxidation of the protein substrate 2, 2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) with greater turnover rates and product yields than myoglobin prepared in solution or MNP alone. Enzymes are often difficult to purify and obtaining high yields for practical applications can be very challenging. Moreover, the electrocatalytic stability and achieving direct electron transfer of purified enzyme films on electrodes is another bottleneck. These challenges are even more drastic in the case of enzymes bound to phospholipid membranes. Despite these limitations, we show that drug metabolizing human liver microsomes, a rather complex enzyme matrix, can be successfully attached to MNPs and immobilized on graphite electrodes with enhanced electrocatalytic activity than microsomal film alone in converting drug into its metabolite. In summary, this presentation will focus on cost-effective development and efficient multiple uses of enzyme catalysts and microsomes for biocatalytic, electrocatalytic, and biosensing applications via magnetic nanomaterials conjugation.