A robust ligand exchange approach for preparing hydrophilic, biocompatible photoluminescent quantum dots

• Aqueous CdSe/ZnS QDs were prepared using polymaleic anhydrides as capping ligand.
• Effect of reaction temperature and time were systematically studied in the synthesis process.
• Water-soluble QDs exhibited a good stability in physiological relevant environment.
• The aqueous QDs were applied as biological probe to detect human embryonic stem cell.

This paper describes a robust ligand exchange approach for preparing biocompatible CdSe/ZnS quantum dots (QDs) to make bioprobe for effective cell imaging. In this method, polymaleic anhydride (PMA) ligand are first used to replace original hydrophobic ligand (oleic acid) and form a protection shell with multiple hydrophilic groups to coat and protect CdSe/ZnS QDs. The as-prepared aqueous QDs exhibit small particle size, good colloidal stability in aqueous solutions with a wide range of pH, salt concentrations and under thermal treatment, which are necessary for biological applications. The use of this new class of aqueous QDs for effective cell imaging shows strong fluorescence signal to human embryonic stem cell, which demonstrate that PMA coated QDs are fully satisfied with the requirements of preparing high quality biological probe.

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