title: Magnetic relaxometry as applied to sensitive cancer detection and localization.
abstract: BACKGROUND
  Here we describe superparamagnetic relaxometry (SPMR), a technology that utilizes highly sensitive magnetic sensors and superparamagnetic nanoparticles for cancer detection. Using SPMR, we sensitively and specifically detect nanoparticles conjugated to biomarkers for various types of cancer. SPMR offers high contrast in vivo, as there is no superparamagnetic background, and bones and tissue are transparent to the magnetic fields.
  
  
  METHODS
  In SPMR measurements, a brief magnetizing pulse is used to align superparamagnetic nanoparticles of a discrete size. Following the pulse, an array of superconducting quantum interference detectors (SQUID) sensors detect the decaying magnetization field. NP size is chosen so that, when bound, the induced field decays in seconds. They are functionalized with specific biomarkers and incubated with cancer cells in vitro to determine specificity and cell binding. For in vivo experiments, functionalized NPs are injected into mice with xenograft tumors, and field maps are generated to localize tumor sites.
  
  
  RESULTS
  Superparamagnetic NPs developed here have small size dispersion. Cell incubation studies measure specificity for different cell lines and antibodies with very high contrast. In vivo animal measurements verify SPMR localization of tumors. Our results indicate that SPMR possesses sensitivity more than 2 orders of magnitude better than previously reported.
authors.forename: Leyma P
authors.initials: LP
authors.lastname: De Haro
authors.forename: Todor
authors.initials: T
authors.lastname: Karaulanov
authors.forename: Erika C
authors.initials: EC
authors.lastname: Vreeland
authors.forename: Bill
authors.initials: B
authors.lastname: Anderson
authors.forename: Helen J
authors.initials: HJ
authors.lastname: Hathaway
authors.forename: Dale L
authors.initials: DL
authors.lastname: Huber
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Matlashov
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Nettles
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Price
authors.forename: Todd C
authors.initials: TC
authors.lastname: Monson
authors.forename: Edward R
authors.initials: ER
authors.lastname: Flynn
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000032:analysis*; D045744:Cell Line, Tumor; D005260:Female; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D058185:Magnetite Nanoparticles; D051379:Mice; D008819:Mice, Nude; D016513:Mice, SCID; D057054:Molecular Imaging / Q000379:methods; D009374:Neoplasms, Experimental / Q000737:chemistry* / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor; D058185:Magnetite Nanoparticles