Fluorescence Labeling and Determination of Pepsin with CdSe Quantum Dots

Abstract

AbstractBased on the solid phase/liquid deposition CdSe quantum dots (QD) were synthesized using selenium and cadmium‐salt as precursor at room temperature. The average diameter of CdSe QD estimated from the high resolution transmission electron microscopy (HRTEM) graph and absorption spectra was ca. 3–3.5 nm. The mercaptoacetic‐acid stabilized CdSe QD exhibited ultraviolet absorption at 350 and 380 nm and strong fluorescence emission at 481.6 nm, respectively. When conjugated with pepsin, the fluorescence peak intensity of CdSe QD decreased considerably and the fluorescence peak shifted to 467.2 nm. Under optimal conditions, a concentration in 5–50 mg· L−1 of pepsin could be determined on the basis of fluorescence decrease ratio of CdSe QD, with a detection limit 3δ of 0.36 mg·L−1 (n=10). The proposed method was applied to detection of the concentration of pepsin in human gastric juice.