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.