Upconversion luminescence-based label-free nanoprobe for dual-readout detection of Tyrosinase

Tyrosinase is the core enzyme in the melanin synthesis process and serves as an important biomarker for the early screening of skin cancer and melanoma. Although the fluorescence method is a highly sensitive method for detecting tyrosinase, its relatively high background fluorescence limits its application in complex matrices. This study combines upconversion nanoparticles (UCNPs) and specific tyrosinase recognition molecules to construct a label-free sensing system for background-free detection of tyrosinase. The prepared nanoprobe employs tyramine as its substrate, which is oxidized by tyrosinase and then reacts further with iron ions to form a purple substance that acts as an energy acceptor, thus quenching the upconversion luminescence of UCNPs (energy donor). Based on the colorimetric reaction and the change in UCL signals, a luminescent-colorimetric dual-readout detection method is constructed, providing the visual detection of tyrosinase. Under optimal conditions, the detection limit of the sensing system is as low as 0.001 U mL^-1 in the luminescent mode, and 0.0025 U mL^-1 in the colorimetric mode. Besides, it exhibits good selectivity in the detection of serum samples. Thus, this efficient, rapid, low-cost, and highly sensitive dual-mode detection method shows great potential in clinical diagnosis applications.