A label-free phosphorescence sensing platform for trypsin based on Mn-ZnS QDs

A label free phosphorescence sensing platform for trypsin was developed employing Mn doped ZnS quantum dots (Mn-ZnS QDs) as the phosphorescence probe. Mn-ZnS QDs can emit strong room temperature phosphorescence. Upon addition of Cytochrome c (Cyt c), a hybrid complex between Mn-ZnS QDs and Cyt c was formed, and consequently, quenched the phosphorescence of Mn-ZnS QDs. In the presence of trypsin, Cyt c was hydrolyzed into small fragments, and accordingly, the quenched phosphorescence of Mn-ZnS QDs went back and high phosphorescence intensity was observed. As such, based on the phosphorescence signal changes of the system, a label free turn-on phosphorescence sensing platform was fabricated. Factors affecting the determination of trypsin including the concentration of Mn-ZnS QDs, reaction time, temperature and pH effect were comprehensively explored. Under the optimal experimental conditions the restored phosphorescence of the sensing system displayed a response for trypsin in the range of 0.88-15.6 mu g mL(-1) with a detection limit of 42 ng mL(-1). Additionally, the sensing platform was successfully applied for the determination of trypsin in human serum samples with satisfactory recovery.