Investigation for labeling of pepsin with CdSe quantum dots synthesized

CdSe quantum dots ( QDs) were multistage synthesized through solid phase/liquid deposition and ethylenediamine solvent at room temperature using selenium and cadmium-salt as precursor. The average size of CdSe QDs estimated from TEM graph is ca. 8 - 10 nm. The applicability of the resulting mercaptoethylic acid modified CdSe QDs to the labeling of pepsin was investigated. The CdSe QDs exhibited strong ultraviolet absorption at 350 and 380 nm and strong fluorescence emission at 481. 6 nm. When interacted with pepsin, fluorescence peak intensity of CdSe QDs decreased considerably as well as fluorescence peak shifted to 467. 2 rim. Under optimal conditions, a concentration of 5 - 50 mg/L of pepsin could be determined on the basis of fluorescence decrease ratio of CdSe QDs, with a detection limit 3 sigma of 0. 36 mg/L ( n = 10). The proposed method was applied to detection of the concentration of pepsin in human gastric juice.