Laccase and peroxidase mimetic CuxO-ZnO microstructures for optical biosensing applications

The development of transition metal oxide nano/microstructures with inherent enzyme-mimicking activity has attracted immense research interest owing to the advantages they offer over natural enzymes. In this work, Cu x O-ZnO microstructures have been utilized to mimic two important enzymes, laccase, and peroxidase. Cu x O-ZnO microstructures with a star-shaped morphology have been synthesized using polyethylene glycol 200 (PEG 200) as a solvent and shape-directing agent. The Cu x O-ZnO microstructures exhibited excellent laccase- and peroxidase-mimicking activities even at harsh conditions, such as elevated temperatures, ionic strength, and varying pH. The laccase-like activity of the nanozyme has been utilized for the colorimetric detection of epinephrine with a detection limit of 0.09 µM. Using the peroxidase-like activity, glutathione and gallic acid have been detected with a limit of detection of 1.35 and 0.15 µM, respectively. The use of such hybrid structures as nanozymes will open up newer avenues for their use in biosensing as well as environmental remediation. Graphical abstract