A novel optical nanoprobe for trypsin detection and inhibitor screening based on Mn-doped ZnSe quantum dots

In this paper, a novel optical nanoprobe (Mn:ZnSe d-dots-Arg₆) for trypsin detection and its inhibitor screening has been constructed successfully based on the fluorescence quenching and recovery of Mn:ZnSe d-dots. Mn:ZnSe d-dots would aggregate in the presence of positively charged Arg₆ (six arginine residues) due to electrostatic interactions that result in the fluorescence quenching. Arg₆ can be hydrolyzed into small fragments in the presence of trypsin, and accordingly, the aggregation of Mn:ZnSe d-dots can be prohibited, which lead to the fluorescence recovery. Experimental results show that the recovery in fluorescence intensity is linearly proportional to the concentration of trypsin within the range of 0.1–12.0 μg mL⁻¹ with a detection limit of 40 ng mL⁻¹ under the optimized experimental conditions. We also prove the feasibility of fluorescence recovery of Mn:ZnSe d-dots for trypsin detection through the resonance light scattering (RLS) technique. Additionally, the optical nanoprobe can be employed for screening the inhibitors of trypsin. The optical nanoprobe was successfully applied for the determination of trypsin in human serum and urine samples with good accuracy and satisfactory recovery.