title: In vivo pharmacokinetics, long-term biodistribution and toxicology study of functionalized upconversion nanoparticles in mice.
abstract: OBJECTIVE
  We investigated the in vivo pharmacokinetics, long-term biodistribution and toxicology of polymer-coated upconversion nanoparticles (UCNPs) in mice.
  
  
  METHODS
  Near infrared emitting Yb(3+)/Tm(3+)-doped NaYF(4) UCNPs coated with either polyethylene glycol (PEG) or polyacrylic acid (PAA) were intravenously injected into mice. Blood levels of UCNPs were measured. Yttrium levels in various organs were measured to determine the biodistribution of UCNPs over 3 months. Serum biochemistry, hematology and histology assays were conducted for in vivo toxicology assays.
  
  
  RESULTS
  UCNP-PEG exhibited improved stability in physiological solutions and prolonged blood circulation half-lives more than UCNP-PAA. No noticeable toxic side effect was noticed for either UCNP-PAA or UCNP-PEG in our toxicology study, despite the long-term retention of those nanoparticles in the reticuloendothelial systems including the liver and spleen of mice.
  
  
  CONCLUSIONS
  Although more systematic investigations are still required, the absence of appreciable toxicity shown in our study encourages future explorations of UCNPs for in vivo biomedical applications.
authors.affiliation: Institute of Functional Nano & Soft Materials Laboratory (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Cheng
authors.forename: Kai
authors.initials: K
authors.lastname: Yang
authors.forename: Mingwang
authors.initials: M
authors.lastname: Shao
authors.forename: Xinhua
authors.initials: X
authors.lastname: Lu
authors.forename: Zhuang
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000818:Animals; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D053758:Nanoparticles / Q000009:adverse effects / Q000737:chemistry*; D036103:Nanotechnology; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D011108:Polymers; D011092:Polyethylene Glycols; C006903:carbopol 940