title: Tumor cell targeting using folate-conjugated fluorescent quantum dots and receptor-mediated endocytosis.
abstract: 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.
authors.affiliation: College of Chemistry and Molecular Sciences, Key Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education and State Key Laboratory of Virology, Wuhan University, Wuhan, People's Republic of China.
authors.forename: Er-Qun
authors.initials: EQ
authors.lastname: Song
authors.forename: Zhi-Ling
authors.initials: ZL
authors.lastname: Zhang
authors.forename: Qing-Ying
authors.initials: QY
authors.lastname: Luo
authors.forename: Wen
authors.initials: W
authors.lastname: Lu
authors.forename: Yun-Bo
authors.initials: YB
authors.lastname: Shi
authors.forename: Dai-Wen
authors.initials: DW
authors.lastname: Pang
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004705:Endocytosis; D005456:Fluorescent Dyes / Q000737:chemistry* / Q000493:pharmacokinetics; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000737:chemistry* / Q000493:pharmacokinetics; D006801:Humans; D007624:KB Cells; D008175:Lung Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D011092:Polyethylene Glycols / Q000737:chemistry / Q000493:pharmacokinetics; D045663:Quantum Dots; D011956:Receptors, Cell Surface / Q000378:metabolism*; D055752:Small Cell Lung Carcinoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology
chemical_list: D002352:Carrier Proteins; D005456:Fluorescent Dyes; D058973:Folate Receptors, GPI-Anchored; D011956:Receptors, Cell Surface; D011092:Polyethylene Glycols; D005492:Folic Acid