Colorimetric assay of phosphate using a multicopper laccase-like nanozyme

A new nanozyme (Cu-NADH) is reported composed of Cu-coordinated nicotinamide adenine dinucleotide (NADH) exhibiting laccase-like activity. The Cu-NADH nanozyme had higher heat tolerance and catalytic efficiency than natural laccase, and its catalytic activity can be enhanced by high concentration of Cl ions and it is intensely inhibited by phosphate. Therefore, a colorimetric method based on Cu-NADH and indigo carmine was successfully developed to detect phosphate in water. This method showed an excellent selectivity for phosphate, and it had a linear relationship in the phosphate concentration range 2-50 μM with a detection limit of 0.37 μM. We believe that this example of coordination between metal ions and biomolecules to mimic natural enzymes can inspire more effective and alternative strategies in nanozyme design and expand their use in sensing and determination.