title: Accelerated stem cell labeling with ferucarbotran and protamine.
abstract: OBJECTIVE
  To develop and characterize a clinically applicable, fast and efficient method for stem cell labeling with ferucarbotran and protamine for depiction with clinical MRI.
  
  
  METHODS
  The hydrodynamic diameter, zeta potential and relaxivities of ferucarbotran and varying concentrations of protamine were measured. Once the optimized ratio was found, human mesenchymal stem cells (MSCs) were labeled at varying incubation times (1-24 h). Viability was assessed via Trypan blue exclusion testing. 150,000 labeled cells in Ficoll solution were imaged with T1-, T2- and T2*-weighted sequences at 3 T, and relaxation rates were calculated.
  
  
  RESULTS
  Varying the concentrations of protamine allows for easy modification of the physicochemical properties. Simple incubation with ferucarbotran alone resulted in efficient labeling after 24 h of incubation while assisted labeling with protamine resulted in similar results after only 1 h. Cell viability remained unaffected. R2 and R2* relaxation rates were drastically increased. Electron microscopy confirmed intracellular iron oxide uptake in lysosomes. Relaxation times correlated with results from ICP-AES.
  
  
  CONCLUSIONS
  Our results show internalization of ferucarbotran can be accelerated in MSCs with protamine, an approved heparin antagonist and potentially clinically applicable uptake-enhancing agent.
authors.affiliation: Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Golovko
authors.forename: Tobias
authors.initials: T
authors.lastname: Henning
authors.forename: Jan S
authors.initials: JS
authors.lastname: Bauer
authors.forename: Marcus
authors.initials: M
authors.lastname: Settles
authors.forename: Thomas
authors.initials: T
authors.lastname: Frenzel
authors.forename: Artur
authors.initials: A
authors.lastname: Mayerhofer
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Rummeny
authors.forename: Heike E
authors.initials: HE
authors.lastname: Daldrup-Link
mesh_terms: D003287:Contrast Media; D003911:Dextrans; D052203:Ferrosoferric Oxide; D006801:Humans; D058185:Magnetite Nanoparticles; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D011479:Protamines; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013194:Staining and Labeling / Q000379:methods; D055815:Young Adult
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D011479:Protamines; C065507:ferumoxides; D052203:Ferrosoferric Oxide