title: Quantum dots are phagocytized by macrophages and colocalize with experimental gliomas.
abstract: OBJECTIVE
  The identification of neoplastic tissue within normal brain during biopsy and tumor resection remains a problem in the operative management of gliomas. A variety of nanoparticles are phagocytized by macrophages in vivo. This feature may allow optical nanoparticles, such as quantum dots, to colocalize with brain tumors and serve as an optical aid in the surgical resection or biopsy of brain tumors.
  
  
  METHODS
  Male Fisher rats (Charles River Labs, Wilmington, MA) were implanted intracranially with C6 gliosarcoma cell lines to establish tumors. Two weeks after the implantation of tumors, 705-nm emission Qdot ITK Amino(PEG) Quantum Dots (Quantum Dot Corp., Hayward, CA) were injected via the tail vein at doses of 3 to 17 nmol. The animals were sacrificed 24 hours after the injection of quantum dots and their tissues were examined.
  
  
  RESULTS
  Quantum dots are avidly phagocytized by macrophages and are taken up by the liver, spleen, and lymph nodes. A dose-response relationship was noted. At low doses, the majority of the quantum dots are sequestered in the liver, spleen, and lymph nodes. At higher doses, increasing quantities of quantum dots are noted within the experimental brain tumors. Macrophages and microglia colocalize with glioma cells, carrying the quantum dot and thereby optically outlining the tumor. Excitation with blue or ultraviolet wavelengths stimulates the quantum dots, which give off a deep red fluorescence detectable with charge-coupled device cameras, optical spectroscopy units, and in dark-field fluorescence microscopy.
  
  
  CONCLUSIONS
  Quantum dots are optical nanoparticles that, when delivered in nanomole doses, are phagocytized by the macrophages and microglia that infiltrate experimental gliomas. The optical signal may be detected, allowing for improved identification and visualization of tumors, potentially augmenting brain tumor biopsy and resection.
authors.affiliation: Brain Tumor Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Heather
authors.initials: H
authors.lastname: Jackson
authors.forename: Osman
authors.initials: O
authors.lastname: Muhammad
authors.forename: Hamid
authors.initials: H
authors.lastname: Daneshvar
authors.forename: Jennifer
authors.initials: J
authors.lastname: Nelms
authors.forename: Alexandra
authors.initials: A
authors.lastname: Popescu
authors.forename: Michael A
authors.initials: MA
authors.lastname: Vogelbaum
authors.forename: Marcel
authors.initials: M
authors.lastname: Bruchez
authors.forename: Steven A
authors.initials: SA
authors.lastname: Toms
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D008264:Macrophages / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008856:Microscopy, Fluorescence / Q000379:methods*; D009374:Neoplasms, Experimental; D009928:Organ Specificity; D010587:Phagocytosis; D045663:Quantum Dots; D051381:Rats; D011916:Rats, Inbred F344; D014018:Tissue Distribution