title: Persistent tissue kinetics and redistribution of nanoparticles, quantum dot 705, in mice: ICP-MS quantitative assessment.
abstract: BACKGROUND
  Quantum dots (QDs) are autofluorescent semiconductor nanocrystals that can be used for in vivo biomedical imaging. However, we know little about their in vivo disposition and health consequences.
  
  
  OBJECTIVE
  We assessed the tissue disposition and pharmacokinetics of QD705 in mice.
  
  
  METHODS
  We determined quantitatively the blood and tissue kinetics of QD705 in mice after single intravenous (iv) injection at the dose of 40 pmol for up to 28 days. Inductively coupled plasma-mass spectrometry (ICP-MS) measurement of cadmium was the primary method of quantification of QD705. Fluorescence light microscopy revealed the localization of QD705 in tissues.
  
  
  RESULTS
  Plasma half-life of QD705 in mice was short (18.5 hr), but ICP-MS analyses revealed QD705 persisted and even continued to increase in the spleen, liver, and kidney 28 days after an iv dose. Considerable time-dependent redistribution from body mass to liver and kidney was apparent between 1 and 28 days postdosing. The recoveries at both time points were near 100%; all QD705s reside in the body. Neither fecal nor urinary excretion of QD705 was detected appreciably in 28 days postdosing. Fluorescence microscopy demonstrated deposition of QD705 in the liver, spleen, and kidneys.
  
  
  CONCLUSIONS
  Judging from the continued increase in the liver (29-42% of the administered dose), kidney (1.5-9.2%), and spleen (4.8-5.2%) between 1 and 28 days without any appreciable excretion, QD705 has a very long half-life, potentially weeks or even months, in the body and its health consequences deserve serious consideration.
authors.affiliation: Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Taiwan.
authors.forename: Raymond S H
authors.initials: RS
authors.lastname: Yang
authors.forename: Louis W
authors.initials: LW
authors.lastname: Chang
authors.forename: Jui-Pin
authors.initials: JP
authors.lastname: Wu
authors.forename: Ming-Hsien
authors.initials: MH
authors.lastname: Tsai
authors.forename: Hsiu-Jen
authors.initials: HJ
authors.lastname: Wang
authors.forename: Yu-Chun
authors.initials: YC
authors.lastname: Kuo
authors.forename: Teng-Kuang
authors.initials: TK
authors.lastname: Yeh
authors.forename: Chung Shi
authors.initials: CS
authors.lastname: Yang
authors.forename: Pinpin
authors.initials: P
authors.lastname: Lin
mesh_terms: D000818:Animals; D007700:Kinetics; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D045663:Quantum Dots; D014018:Tissue Distribution