Bioinorganic Chemistry Approach to Nanozymes for Cellular Redox Regulation

Organic/metal organic compounds that mimic the functional role of enzymes have been extensively investigated. Recently, few nanomaterials such as gold nanoparticles, ferromagnetic nanoparticles and graphene-based materials have been innovatively shown to exhibit unprecedented biochemical catalysis by mimicking certain enzymes (nanozymes). Owing to their simplicity of preparation and storage and stability, nanozymes have been investigated for their application in many fields such as biosensing, immunoassays, cancer diagnostic, therapeutic and pollutant removal, etc. Despite current interest on nanozymes, tackling with some of the difficulties associated with them such as selectivity, cooperativity with other enzymes, limited surface area due to functionalization, biocompatibility and activity in cells, etc. is a challenging task.
 
In this seminar, I will discuss about the novel antioxidant and phosophotriesterase nanozymes. We have recently reported the graphene-hemin hybrid material for its remarkable peroxynitrite reductase and isomerase antioxidant activities. Noncovalent interactions of hemin and reduced graphene oxide (RGO) resulted in synergistic activity to effectively scavenge peroxynitrite, which is a potent reactive nitrogen species (RNS) found in vivo.
 
In another related study, we found that vanadium pentoxide (V₂O₅), an oxidant, reveals an unexpected antioxidant role in its nano-form and exerts tremendous cytoprotective effects. The vanadia nanozyme exhibit excellent glutathione peroxidase (GPx)-like catalytic antioxidant activity and prevents oxidative damage to cells from reactive oxygen species (ROS) without affecting the expression level of other antioxidant enzymes. This work demonstrates the first experimental evidence that the biological property of a metal ion in its nano-form can be completely different from that of a bulk material. In a similar line, I will also briefly highlight about MnFe₂O₄ nanooctahedrons as oxidase and vacancy-engineered nanoceria as phosphotriesterase nanozymes for antibody-free detection of major biomarkers of oxidative stress and detoxification of sarin gas-related nerve agents, respectively.