Construction of platinum nanozyme by using carboxymethylcellulose with improved laccase-like activity for phenolic compounds detection

Natural laccases are multicopper oxidases widely applied in enzymatic biotransformation. However, using natural laccases in real-world settings is expensive and usually hampered by their stability. Most reported laccase-like nanozymes are limited to copper-containing, while other materials have yet to receive sufficient attention. Herein, platinum (Pt) nanoparticles (NPs) have been constructed as a laccase-like nanozyme using sodium carboxymethylcellulose (CMC-PtNPs). The as-prepared CMC-PtNPs have small particle size (3.79 ± 0.03 nm), good dispersion, and clear interaction mode between polysaccharides and nanozyme. CMC-PtNPs were found to own applicable laccase-like activity by producing O2•− as oxidants to oxidize laccase-related substrates. According to the steady-state dynamic assay, the apparent Km value of CMC-PtNPs was calculated as 0.218 mM. Compared with natural laccase or laccase-like materials, the laccase-like CMC-PtNPs have the advantage of higher substrate affinity and catalytic effect. More significantly, CMC-PtNPs were found to be highly stable at wide-ranged pH and temperature. On a practical level, the adequacy of the developed CMC-PtNPs was also confirmed by the efficient detection of the laccase-related phenolic compounds (e.g., 2,4-dichlorophenol, dopamine, noradrenaline, and adrenaline). A highly linear relationship (R2 = 0.996) was obtained by plotting the absorbance at 510 nm and 2,4-DCP concentration in a range of 6.25–225 μM with a low limit of detection (LOD) of 900 nM. Also, the colorimetric sensor exhibited outstanding sensing performance toward other phenolic compounds. Looking forward, this work provides a new design of laccase-like Pt nanozyme and demonstrates its utilization potentiality in nanozyme research, environmental remediation, and other fields.