Effective reduction of non-specific binding by bovine serum albumin modified quantum dot surface for cell targeted imaging

Abstract

Exploiting the bright and colorful photophysical properties of semiconductor quantum dots (QDs) is an onward trend in biotechnology and QDs have been widely used as fluorescent probes in cell-targeted imaging. However, nonspecific binding to cellular membranes has been a major challenge. In this study, high quality cadmium telluride (CdTe) quantum dots with different particle sizes were prepared via hydrothermal method. The surface of the QDs was modified with the chemically reduced bovine serum albumin (BSA) for effective reduction of nonspecific binding in cell targeting. Here,the as–prepared QDs exhibits tunable photoluminescence (PL) emission between 525nm and 620 nm.BSA-coated QDs which also provide reaction sites for conjugation of targeting ligands is mainly achieved by multiple mercapto groups in BSA macromolecules as multidentate ligands and partially by ligand exchange interaction between BSA and QDs. The BSA-coated QDs, with an overwhelming majority of hydrodynamic diameter size of 15nm ,are found to exhibit strong fluorescent intensities. The cellular uptake and localization of QDs was studied using laser confocal scanning microscopy. The results indicated that the nonspecific cellular binding is effectively reduced by BSA-coated QDs, compared with the N-acetyl-L-cysteine (NAC) -coated CdTe QDs.