Citrate-Capped Iridium Nanoparticles as Peroxidase Mimics with High Catalytic Efficiency

Over time, noble-metal nanostructures have sparked interest as peroxidase mimics for in-vitro diagnostics, with emphasis on inflammatory pathogenesis such as cancer. Recent advancements focusing on improving the catalytic efficiency of currently used synthetic and natural peroxidases towards future clinical applications such as Point of Care (POC) settings are being studied. Efforts in exploiting the size-dependent and physicochemical properties of noble metal nanoparticles to achieve superior catalytic performance may serve as excellent alternatives to traditional peroxidases. Here, we introduce a facile protocol to engineer citrate-capped iridium nanoparticles (Ir NPs) to study their efficacy as peroxidase mimics towards future applications as secondary antibody-labels in in-vitro diagnostic (IVD) techniques. Our inspiration for choosing to explore Ir NPs stems from the following (i) recent studies demonstrating Ir-based nanostructures with excellent catalytic performance (ii) the successful catalytic decomposition of hydrogen peroxide in the presence of Ir, revealing peroxidase-like behavior, (iii) activity of Ir NPs at high temperatures, rendering them stable and promising for hydrothermal synthesis. In this work, we successfully engineered citrate-capped Ir NPs with superior catalytic efficiency at the level of 106 – 107 s-1. We hope this work serves as an inspiration to explore the implementation of Ir NPs in practical applications