Detection of tyramine and tyrosinase activity using red region emission NaGdF4:Yb,Er@NaYF4 upconversion nanoparticles.

A selective, simple and environment-friendly type fluorescence sensing platform between upconversion nanoparticles (UCNPs) and melanin-like polymer utilizing the photoinduced electron-transfer (PET) mechanism was developed. The effective fluorescence quenching of UCNPs by melanin-like polymers could detect tyramine and tyrosinase (TYR) activity through the bio-catalysed oxidation of tyramine to the melanin-like polymer products. At optimal conditions, the range of linearity in detection was 0.167-33.3 μΜ for tyramine, and the limit of detection of tyramine was 0.026 μΜ. The linear range of TYR was 0.0033-1 U·mL-1, and the limit of detection of TYR was 0.003 U·mL-1. Furthermore, the strategy could be applied to real sample analysis with satisfactory results.