Fabrication And Application Of Biomacromolecules-QDs Assemblies Via Soft-Binding Ligand Capped Photoluminescent CdSe/ZnS Quantum Dots

With last decade, quantum dots (QDs) relative materials have emerged as great tools of bio-application due to their unique photoluminescence and excellent stability. In this article, a kind of QDs-biomacromolecules assembly was prepared as cell imaging agents in laboratory. In order to obtain QDs-biomacromolecules assembly successfully, a novel concept that soft-binding ligands of QDs was proposed. The soft-binding ligand, amino-propanol (APP), could directly exchange the original ligands on the QDs surface which are extremely hydrophobic. After the ligand exchange, the resultant APP capped QDs were soluble in several polar organic solvent, such as dimethyl sulfoxide (DMSO), dimethyl formamide (DMF) and tetrahydrogen furan (THF). The photoluminescence of QDs was strongly reserved and the morphologies were not deteriorated. The soft-binding property of APP capped QDs was evaluated by water treatment. The result showed more than 80% APP ligands were detached after water treatment.Meanwhile, in order to integrate the QDs with biomacromolecules, the solubility of biomacromolecules should be improved. By simple grafting with glycidol, the solubility of chitosan was improved obviously. Owing to the reduction of the inner-molecular hydrogen bonds, the glycidol-chitosan derivation was highly soluble in water and polar organic solvent such as DMSO and DMF. Taking advantages of the improvement of the solubility, the amphiphilic graft copolymer, glycidol-chitosan-graft-polycaprolactone, was synthesized in DMSO homogeneously. The resultant copolymer could be applied in drug delivery system as a micellular carrier.Finally, the QDs-biomacromolecules assembly could be prepared in homogeneous solvent with a mild dialysis process. The glycidol-chitosan, amphiphilic copolymer and heparin were successfully integrated with the QDs capped with soft-binding ligands. For glycidol-chitosan-QDs assembly, the size and surface charge of the assembly truly depends on the QDs content. On contrary, the size and surface charge of amphiphilic copolymer and heparin-QD assemblies were independent on QD content. The cytotoxicity was not increased by adding the QDs, and the quantum yield of the assemblies were up to 10% which is appropriate for cell imaging. Observing by laser confocal microscope, the cell imaging was achieved in a HepG2 cell line.The QDs capped with soft-binding ligand could encourage the fabrication of QDs system with new process. Also, the QDs-biomacromolecules assembly could be a potential cell imaging system with high efficiency and safety.