title: In vivo distribution of polymeric nanoparticles at the whole-body, tumor, and cellular levels.
abstract: OBJECTIVE
  Block copolymer micelles (BCMs) were functionalized with indium-111 and/or epidermal growth factor (EGF), which enabled investigation of the in vivo transport of passively and actively targeted BCMs. The integration of conventional and image-based techniques afforded novel quantitative means to achieve an in-depth insight into the fate of polymeric nanoparticles in vivo.
  
  
  METHODS
  Pharmacokinetics and biodistribution studies were performed in athymic mice bearing human breast xenografts to evaluate the whole-body transport of NT-BCMs (non-targeted, EGF-) and T-BCMs (targeted, EGF+). The intratumoral distribution of BCMs was investigated using MicroSPECT/CT and autoradiographic imaging, complemented with quantitative MATLAB® analyses. Tumors were fractionated for quantifying intracellular uptake of BCMs via γ-counting.
  
  
  RESULTS
  The intratumoral distribution of NT-BCMs and T-BCMs were found to be heterogeneous, and positively correlated with tumor vascularization (r>0.68 ± 0.04). The enhanced in vivo cell uptake and cell membrane binding of T-BCMs were found to delay their clearance from tumors overexpressing EGFR, and therefore resulted in enhanced tumor accumulation for the T-BCMs in comparison to the NT-BCMs.
  
  
  CONCLUSIONS
  Adequate passive targeting is required in order to achieve effective active targeting. Tumor physiology has a significant impact on the transvascular and intratumoral transport of passively and actively targeted BCMs.
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College St., Toronto, Ontario, Canada.
authors.forename: Helen
authors.initials: H
authors.lastname: Lee
authors.forename: Bryan
authors.initials: B
authors.lastname: Hoang
authors.forename: Humphrey
authors.initials: H
authors.lastname: Fonge
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Reilly
authors.forename: Christine
authors.initials: C
authors.lastname: Allen
mesh_terms: D000818:Animals; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D008823:Micelles; D053758:Nanoparticles; D010599:Pharmacokinetics; D011108:Polymers; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D008823:Micelles; D011108:Polymers