Effective Reduction of Nonspecific Binding by Surface Engineering of Quantum Dots with Bovine Serum Albumin for Cell-Targeted Imaging

Abstract

Quantum dots (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, a new approach is developed for effective reduction of nonspecific binding by bovine serum albumin (BSA)-coated QDs in cell targeting. The experimental results show efficient transfer of hydrophobic QDs from organic to aqueous phase in the presence of BSA aqueous solution under ultrasonication. This ultrasonication-based approach is facile, rapid, and efficient. Stabilization of QDs is mainly achieved by multiple mercapto groups in BSA macromolecules as multidentate ligands and partially by hydrophobic interaction between BSA and pending fatty ligands on QDs. The water solubility of QDs is enhanced by the surface amino and carboxyl groups, which also provide reaction sites for conjugation of targeting ligands. The BSA-coated QDs, with an overwhelming majority of hydrodynamic diameter size of ca. 18 nm, are colloidally stable under both acidic and basic conditions and found to exhibit strong fluorescent intensities. The nonspecific cellular binding is effectively reduced by BSA-coated QDs, compared with the mercaptopropionic acid (MPA)-coated CdTe QDs. BSA-coated QDs are further functionalized with cyclic Arg-Gly-Asp (cRGD) peptide. The cell assays indicate their high target-selectivity in integrin α(v)β(3)-expressed cell imaging.

Surface engineered antifouling optomagnetic SPIONs for bimodal targeted imaging of pancreatic cancer cells

“…[33][34][35] Based on the unique structure of BSA, it was found that the QDs were effectively surface functionalized under ultrasonication. 21 However, SPIONs were found to cluster at an average size of 100 nm. 22 In this study, a transition process by NOBF 4 was introduced to the surface functionalization of SPIONs.…”

“…29 However, in the course of dialysis against water, the inhibition of DMF decreases along with DMF being diluted gradually in the samples. Therefore, hydrophilic BSA can be anchored onto the surfaces of SPIONs by means of its chemical groups with appreciable metal affinity, 21 resulting in enhanced solubility of BSA⋅SPIONs in water.…”

“…In our previous work, we used BSA as the stabilizer and capping biopolymer, and successfully transferred hydrophobic quantum dots (QDs) and SPIONs into the hydrophilic phase under ultrasonication conditions. 21,22 The BSA coated QDs exhibited excellent antifouling property. The only difference found between the SPIONs and QDs was that the former clustered considerably while the latter individually dispersed in water solution.…”

“…This is mainly attributed to the varied affinity of BSA from QDs to SPIONs. 21,22 The SPIONs formed clusters of nearly 100 nm and showed appreciable MRI as a result of high uptake in liver. However, for the nonreticuloendothelial system, the nanoparticles must be kept small enough to escape the reticuloendothelial system for prolonged blood circulation time.…”

“…21 The abundant amino/ carboxyl groups of BSA are favorable to post surface modifications with other functional materials such as antibody and fluorescent dye.…”