Polymer-Assisted Engineering of Copper Peroxide Nanozymes with Enhanced Laccase-like Activity for Sensing Applications

Nanozymes have emerged as promising alternatives to natural enzymes, but their relatively low catalytic activity and limited stability present significant challenges to design nanozymes with a performance comparable to that of natural enzymes. Engineering nanomaterials through surface functionalization offers a promising approach to meet these demands by providing tunable surface properties for molecular recognition, enhanced catalytic activity, long-term stability under ambient conditions, and improved biocompatibility. In this study, we employed a surface modulation strategy by using different polymeric scaffolds to stabilize copper peroxide (CP) nanodots to modulate their laccase-like nanozyme activity. Five different polymers having variable surface charge (cationic, anionic, and neutral) and hydrophobicity were selected for the fabrication of CP nanodots. Among different surface-engineered nanodots, cationic functionalized nanodots possess the highest laccase-like activity, which was found to be 10-fold higher than natural laccase enzymes. High nanozyme activity was supported through colloidal stability, redox activity of the Cu center, and substrate interaction with the nanozyme, which was evaluated by several experiments, where it was found that the catalytic activity of CP nanodots can be understood as the result of fine-tuning the balance between surface-substrate interactions and copper electrophilicity, which is strongly influenced by the choice of stabilizing polymer. The high laccase-like nanozyme activity of CP-nanodots was leveraged for the detection of catecholamine-based neurotransmitters, whose dysregulation is associated with various pathological conditions, particularly neurological disorders. Furthermore, the observed variation in enzymatic activity induced by different surface polymer coatings inspired the development of a sensor array for the detection of antibiotics based on differential molecular interactions. To this end, a set of five polymer-functionalized CP nanodots were considered to construct a sensor array capable of detecting multiple antibiotics with high sensitivity, achieving a limit of detection (LOD) as low as 100 nM. Overall, this approach provides valuable insights for designing nanozymes with tunable nanozyme activity by surface modulation, along with highlighting their potential applications in the discrimination of antibiotics and other biomarkers.