title: Real time in vivo non-invasive optical imaging using near-infrared fluorescent quantum dots.
abstract: OBJECTIVE
  Deep-tissue optical imaging is of particular interest, as the equipment costs are lower than for competing technologies such as MRI. For this purpose, the development of novel contrast agents with near-infrared (NIR) fluorescence is especially important. We report on the use of NIR semiconductor nanocrystals in deep-tissue in vivo optical imaging.
  
  
  METHODS
  Semiconductor nanocrystals of CdMnTe/Hg were grown in aqueous solution and then coated with bovine serum albumin (BSA). The nanocrystals were approximately 5 nm in diameter and have a broad fluorescence peak in the NIR (770 nm). Nanocrystals were injected either subcutaneously or intravenously into athymic NCR NU/NU and C3H/HENCR MTV mice and then excited with a spatially broad 633 nm source; the resulting fluorescence was captured with a sensitive CCD camera.
  
  
  RESULTS
  We have demonstrated that the nanocrystals are a useful angiographic contrast agent for vessels surrounding and penetrating a murine squamous cell carcinoma in a C3H mouse. Preliminary assessment of the depth of penetration for excitation and emission was done by imaging a beating mouse heart, both through an intact thorax and after a thoracotomy. The temporal resolution associated with imaging the nanocrystals in circulation has been addressed, and the blood clearance for this contrast agent has also been measured.
  
  
  CONCLUSIONS
  There was no significant photobleaching or degradation of the nanocrystals after an hour of continuous excitation. The stability of the nanocrystals together with the time resolution of the optical detection makes them particularly attractive candidates for pharmacokinetic imaging studies.
authors.affiliation: National Institutes of Health, Bethesda, MD 20892, USA. morgann@mail.nih.gov
authors.forename: Nicole Y
authors.initials: NY
authors.lastname: Morgan
authors.forename: Sean
authors.initials: S
authors.lastname: English
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Victor
authors.initials: V
authors.lastname: Chernomordik
authors.forename: Angelo
authors.initials: A
authors.lastname: Russo
authors.forename: Paul D
authors.initials: PD
authors.lastname: Smith
authors.forename: Amir
authors.initials: A
authors.lastname: Gandjbakhche
mesh_terms: D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000098:blood supply; D003287:Contrast Media; D003331:Coronary Vessels / Q000033:anatomy & histology; D005260:Female; D005453:Fluorescence; D006321:Heart / Q000033:anatomy & histology; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007259:Infrared Rays; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D051379:Mice; D008809:Mice, Inbred C3H; D008815:Mice, Inbred Strains; D008819:Mice, Nude; D049329:Nanostructures; D010781:Photography / Q000295:instrumentation / Q000379:methods; D045663:Quantum Dots; D012710:Serum Albumin, Bovine; D012983:Soft Tissue Neoplasms / Q000098:blood supply
chemical_list: D003287:Contrast Media; D012710:Serum Albumin, Bovine