Self-Catalyzed, Self-Limiting Growth Of Glucose Oxidase-Mimicking Gold Nanoparticles

Size and shape of nanoparticles are generally controlled by external influence factors such as reaction temperature, time, precursor, and/or surfactant concentration. Lack of external influence may eventually lead to unregulated growth of nanoparticles and possibly loss of their nanoscale properties. Here we report a gold nanoparticle (AuNPs)-based self-catalyzed and self-limiting system that exploits the glucose oxidase-like catalytic activity of AuNPs. The Michaelis (?) Menten constant (Km) of AuNPs was calculated to be 6.97 mM, which was slightly higher than GOx (4.87 mM) slightly lower affinity. Of note, the GOx-mimicking activity was not oberved in a range of interrogated nanomaterials, such as silver nanoparticles, TiO2 nanoparticles, carbon nanotubes, and Fe3O4 nanoparticles. We investigated the catalytic activity of AuNPs systematically. Interestingly, AuNPs exhibited superior pH, thermal, and storage stability to natural enzyme GOx. By using AuNPs of different size (13,20,30, and 50nm) at the same concentration, we found that the catalytic activity of AuNPs decreased along with their sizes. We find that the AuNP-catalyzed glucose oxidation in situ produces hydrogen peroxide (H2O2) that induces the AuNPs'seeded growth in the presence of chloroauric acid (HAuC14). This crystal growth of AuNPs is internally regulated via two negative feedback factors, size-dependent activity decrease of AuNPs and product (gluconic acid)-induced surface passivation, leading to a rapidly self-limiting system. Interestingly, the size, shape, and catalytic activities of AuNPs are simultaneously controlled in this system. We expect that it provides a new method for controlled synthesis of novel nanomaterials, design of "smart" self-limiting nanomedicine, as well as in-depth understanding of self-limiting systems in nature.