Robust and Reusable Laccase Mimetic Copper Oxide Nanozyme for Phenolic Oxidation and Biosensing

The development of earth-abundant metal-oxide-based nanomaterials with an intrinsic enzyme-mimicking activity (nanozyme) is useful for both practical applications and fundamental research. The laccase enzyme is a multicopper oxidase that finds commercial utility in environmental remediation and biotechnology, but with significant limitations under harsh conditions. Herein, we present the laccase-like activity of Cu2O nanospheres, fabricated using a one-pot polyol-based microwave-assisted method. The as-synthesized Cu2O nanospheres possess great stability under harsh conditions and exhibit excellent laccase-like activity with a KM value of 0.2 mM, considerably smaller than those of previously reported nanozymes as well as native laccase. The utility of the nanozyme was demonstrated in the efficient oxidation of phenolic pollutants under real-life high-salinity conditions, as well as in the colorimetric detection of biomolecules such as epinephrine and dopamine with sensitivities of 10 and 6.5 μM, respectively. Notably, the Cu2O nanozyme enabled naked-eye detection of the acetylcholinesterase enzyme with a biorelevant sensitivity (2.5 pM). This robust and recyclable laccase-mimicking nanozyme introduces a simple and cost-effective metal oxide platform that would find multiple practical applications in environmental remediation, catalysis, and biosensing.