Visual and Fluorescent Detection of Tyrosinase Activity\nby Using a Dual-Emission Ratiometric Fluorescence Probe

Abstract

In\nthis work, we designed a dual-emission ratiometric fluorescence\nprobe by hybridizing two differently colored quantum dots (QDs), which\npossess a built-in correction that eliminates the environmental effects\nand increases sensor accuracy. Red emissive QDs were embedded in the\nsilica nanoparticle as reference while the green emissive QDs were\ncovalently linked to the silica nanoparticle surface to form ratiometric\nfluorescence probes (RF-QDs). Dopamine (DA) was then conjugated to\nthe surface of RF-QDs via covalent bonding. The ratiometric fluorescence\nprobe functionalized with dopamine (DA) was highly reactive toward\ntyrosinase (TYR), which can catalyze the oxidization of DA to dopamine\nquinine and therefore quenched the fluorescence of the green QDs on\nthe surface of ratiometric fluorescence probe. With the addition of\ndifferent amounts of TYR, the ratiometric fluorescence intensity of\nthe probe continually varied, leading to color changes from yellow-green\nto red. So the ratiometric fluorescence probe could be utilized for\nsensitive and selective detection of TYR activity. There was a good\nlinear relationship between the ratiometric fluorescence intensity\nand TYR concentration in the range of 0.05–5.0 μg mL^–1, with the detection limit of 0.02 μg mL^–1. Significantly, the ratiometric fluorescence probe\nhas been used to fabricate paper-based test strips for visual detection\nof TYR activity, which validates the potential on-site application.