A fluorescence resonance energy transfer biosensor based on carbon dots and gold nanoparticles for the detection of trypsin

Herein we propose a fluorescence turn-on strategy for the sensitive and selective detection of trypsin based on fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and amino-functionalized carbon dots (C-dots). In this assay, C-dots were treated as fluorometric reporter, while AuNPs were treated as fluorescence quencher. A specially designed negatively charged short peptide chain with one functioned cysteine group as the substrate for trypsin. The sensor works as follows: the negatively charged part of the peptide can be hydrolyzed by trypsin, resulting in the releasing of shorter and positively charged peptides. These shorter peptides then induces AuNPs aggregation due to the strong electrostatic interaction between positively charged peptides and the negatively charged AuNPs, thus leading to the restoration of the FRET-quenched fluorescence emission of C-dots. Measuring the changes in the fluorescence of C-dots, the concentrations of trypsin can be determined. Under the optimized conditions, we achieved quantitative evaluation of trypsin in a range of 2.5-80 ng mL(-1) with the detection limit of 0.84 ng mL(-1). Meanwhile, this sensing system also exhibited excellent selectivity and sensitivity for trypsin, and we successfully applied it for the detection of trypsin in human serum samples. Based on the above findings, we conclude that this new FRET based sensor might be significant in disease diagnosis in the future.