Received on June 30, 2008
Accepted on January 22, 2009

Automation and Analytical Techniques

Tumor Cell Targeting Using Folate-Conjugated Fluorescent Quantum Dots and Receptor-Mediated Endocytosis

¹ College of Chemistry and Molecular Sciences and State Key Laboratory of Virology, Wuhan University, Wuhan, People's Republic of China
² Section on Molecular Morphogenesis, Program on Cell Regulation and Metabolism, National Institute of Child Health and Human Development, NIH, Bethesda, MD

^* To whom correspondence should be addressed. E-mail: dwpang{at}whu.edu.cn.

BACKGROUND: Luminescent nanobioprobes with cell-targeting specificity are likely to find important applications in bioanalysis, biomedicine, and clinical diagnosis. Quantum dots (QDs) are unique and promising materials for such a purpose because of their fluorescence and large surface area for attaching cell-targeting molecules.

METHODS: We produced water-dispersible QDs by coating hydrophobic QDs with small amphiphilic polyethylene glycol (PEG) molecules via hydrophobic interactions. We covalently coupled folate (FA) onto the water-dispersible PEG-coated QDs (PEG-QDs) to produce FA-coupled PEG-QDs (FA-PEG-QDs).

RESULTS: These FA-PEG-QD nanoparticles functioned as fluorescent nanobioprobes that specifically recognized folate receptors (FRs) overexpressed in human nasopharyngeal cells (KB cells) but not in an FR-deficient lung carcinoma cell line (A549 cells). Using confocal fluorescence microscopy, we demonstrated uptake of FA-PEG-QDs by KB cells but no uptake of folate-free PEG-QDs. The specificity of this receptor-mediated internalization was confirmed by comparing the uptake by KB vs A549 cells.

CONCLUSIONS: Our results suggest that such cell-targeting fluorescent nanobioprobes are potentially very powerful tools for recognizing target cells and delivering and tracking drugs and other therapeutic materials.