An ultra-sensitive and label-free fluorescent probe for trypsin and inhibitor based on DNA hosted Cu nanoclusters

In this paper, we developed a simple, ultra-sensitive and label-free fluorescent probe for trypsin and its inhibitor based on DNA hosted Cu nanoclusters (Cu NCs). Fluorescent Cu nanoclusters with maximum emission wavelength of 591 nm are formed by using double-stranded DNA (dsDNA) as templates. With the addition of protamine, the fluorescence intensity (FL) of Cu NCs could be enhanced obviously through forming protamine/DNA complexes between Cu NCs and protamine. The fluorescence intensity of Cu NCs would decrease in the present of trypsin due to the protamine hydrolysis, which allows the sensitive detection of trypsin in the range of 0.1-1000 ng mL(-1). The detection limit for trypsin is 0.048 ng mL(-1). And this system was further used for trypsin inhibitor detection. Compared with the previous reports, this method does not need complex DNA sequence design, fluorescence label and has a much lower detection limit. (C) 2015 Elsevier B.V. All rights reserved.