Engineering nickel-supported osmium bimetallic nanozymes with specifically improved peroxidase-like activity for immunoassay

Researchers have shown significant interest in modulating the peroxidase-like activity of nanozymes. Among these, bimetallic nanozymes have shown superior peroxidase-like activity over monometallic counterparts, offering enhanced performance and cost-efficiency in nanozyme designs. Herein, bimetallic nanozymes comprising nickel (Ni) and osmium (Os) incorporated into hyaluronate (HA) have been developed, resulting in HA-Nin/Os nanoclusters. Subsequently, comprehensive characterizations have been conducted. Further investigation has revealed that HA-Nin/Os efficiently catalyzed 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation with hydrogen peroxide (H2O2), confirming its peroxidase-like behavior and role as a nanozyme. Impressively, HA-Ni2/Os (Ni/Os = 2:1) displays heightened substrate affinity, accelerated reaction rates, enhanced hydroxyl radical production in acidic conditions, and exhibits activity unit of 1224 U/mg, representing more than two-fold increase compared to non-Ni-supported Os nanozyme. Theoretical calculations indicate that Ni support enhances the peroxidase-like process of Os nanozyme by improving H2O2 adsorption and TMB oxidation. Crucially, the support of Ni does not significantly alter the other enzyme-like activities of Os nanozymes, thereby enabling Ni to selectively enhance their peroxidase-like activity. In terms of application, the peroxidase-like ability of HA-Ni2/Os, facilitated by HA's carboxyl groups enabling crosslinking, proves effective in a squamous carcinoma antigen immunoassay. Moreover, HA-Ni2/Os exhibit reliable stability, promising as a peroxidase substitute. This work underscores the advantages of incorporating Ni into Os, specifically enhancing peroxidase-like activity, highlighting the potential of Os bimetallic nanozymes for peroxidase-based applications.