A novel fluorescence biosensor for sensitivity detection of tyrosinase and acid phosphatase based on nitrogen-doped graphene quantum dots

Highlights: • Strongly fluorescent N-GQDs were successfully prepared by hydrothermal method. • A novel fluorescent biosensor for label-free detection of TYR and ACP was established based on the N-GQDs. • Good sensitivity and selectivity were obtained. • This method was utilized to detect TYR and ACP in real sample with satisfactory results. - Abstract: In this paper, we developed a sensitive fluorescence biosensor for tyrosinase (TYR) and acid phosphatase (ACP) activity detection based on nitrogen-doped graphene quantum dots (N-GQDs). Tyrosine could be catalyzed by TYR to generate dopaquinone, which could efficiently quench the fluorescence of N-GQDs, and the degree of fluorescence quenching of N-GQDs was proportional to the concentration of TYR. In the presence of ACP, l-Ascorbic acid-2-phosphate (AAP) was hydrolyzed to generate ascorbic acid (AA), and dopaquinone was reduced to l-dopa, resulting in the fluorescence recovery of the quenched fluorescence by dopaquinone. Thus, a novel fluorescence biosensor for the detection of TYR and ACP activity based on N-GQDs was constructed. Under the optimized experimental conditions, the fluorescence intensity was linearly correlated with the concentration of TYR and ACP in the range of 0.43–3.85 U mL⁻¹ and 0.04–0.7 mU mL⁻¹ with a detection limit of 0.15 U mL⁻¹ and 0.014 mU mL⁻¹, respectively. The feasibility of the proposed biosensor in real samples assay was also studied and satisfactory results were obtained.