One-pot cascade catalysis at neutral pH driven by CuO tandem nanozyme for ascorbic acid and alkaline phosphatase detection

During the past decades, most reported nanozymes have been confined to limited species of enzyme-like activities and only few examples were reported to mimic tandem enzyme-like activities. To fill gaps in expanding the species and improving catalytic efficiency of nanozymes, exploring nanozymes as tandem nanozymes has turned out to be an effective method. Herein, we have presented the cupric oxide nanoparticles (CuO NPs) as tandem nanozymes, which is expected to simultaneously catalyze the cascade reaction coupling ascorbate oxidase with peroxidase like activities at temperature (45 °C) and neutral pH (pH = 7). This one-pot cascade reaction system included the oxidation of ascorbic acid (AA) to yield H2O2 and terephthalic acid (TA) oxidation reaction mediated by H2O2 to generate a fluorescence product (λex = 315 nm, λem =422 nm). More significantly, fluorescent sensors are respectively fabricated for AA, alkaline phosphatase (ALP) and l-phenylalanine (ALP inhibitor) detection coupling the catalysis of CuO tandem nanozymes with ALP enzymatic reaction. Base on these findings, this work shows high selectivity/sensitivity and low limit of detection (2.92 × 10−8 M for AA, 0.058 U/L for ALP) properly due to an in-situ reaction. CuO tandem nanozymes expand the species of nanozymes and these CuO tandem nanozymes based fluorescent sensors can be applied for one-pot nonenzymatic biomolecular sensing in clinical diagnostics, biological or pharmaceutical analysis.