title: Tissue distribution and excretion kinetics of orally administered silica nanoparticles in rats.
abstract: OBJECTIVE
  The effects of particle size on the tissue distribution and excretion kinetics of silica nanoparticles and their biological fates were investigated following a single oral administration to male and female rats.
  
  
  METHODS
  Silica nanoparticles of two different sizes (20 nm and 100 nm) were orally administered to male and female rats, respectively. Tissue distribution kinetics, excretion profiles, and fates in tissues were analyzed using elemental analysis and transmission electron microscopy.
  
  
  RESULTS
  The differently sized silica nanoparticles mainly distributed to kidneys and liver for 3 days post-administration and, to some extent, to lungs and spleen for 2 days post-administration, regardless of particle size or sex. Transmission electron microscopy and energy dispersive spectroscopy studies in tissues demonstrated almost intact particles in liver, but partially decomposed particles with an irregular morphology were found in kidneys, especially in rats that had been administered 20 nm nanoparticles. Size-dependent excretion kinetics were apparent and the smaller 20 nm particles were found to be more rapidly eliminated than the larger 100 nm particles. Elimination profiles showed 7%-8% of silica nanoparticles were excreted via urine, but most nanoparticles were excreted via feces, regardless of particle size or sex.
  
  
  CONCLUSIONS
  The kidneys, liver, lungs, and spleen were found to be the target organs of orally-administered silica nanoparticles in rats, and this organ distribution was not affected by particle size or animal sex. In vivo, silica nanoparticles were found to retain their particulate form, although more decomposition was observed in kidneys, especially for 20 nm particles. Urinary and fecal excretion pathways were determined to play roles in the elimination of silica nanoparticles, but 20 nm particles were secreted more rapidly, presumably because they are more easily decomposed. These findings will be of interest to those seeking to predict potential toxicological effects of silica nanoparticles on target organs.
authors.affiliation: Department of Food Science and Technology, Seoul Women's University, Seoul, Republic of Korea.
authors.forename: Jeong-A
authors.initials: JA
authors.lastname: Lee
authors.affiliation: Department of Food Science and Technology, Seoul Women's University, Seoul, Republic of Korea.
authors.forename: Mi-Kyung
authors.initials: MK
authors.lastname: Kim
authors.affiliation: Department of Food Science and Technology, Seoul Women's University, Seoul, Republic of Korea.
authors.forename: Hee-Jeong
authors.initials: HJ
authors.lastname: Paek
authors.affiliation: Department of Biochemistry and Molecular Biology, Korea University Medical School and College, Seoul, Republic of Korea.
authors.forename: Yu-Ri
authors.initials: YR
authors.lastname: Kim
authors.affiliation: Department of Biochemistry and Molecular Biology, Korea University Medical School and College, Seoul, Republic of Korea.
authors.forename: Meyoung-Kon
authors.initials: MK
authors.lastname: Kim
authors.affiliation: Toxicological Research Division, National Institute of Food and Drug Safety Evaluation, Chungchungbuk-do, Republic of Korea.
authors.forename: Jong-Kwon
authors.initials: JK
authors.lastname: Lee
authors.affiliation: Toxicological Research Division, National Institute of Food and Drug Safety Evaluation, Chungchungbuk-do, Republic of Korea.
authors.forename: Jayoung
authors.initials: J
authors.lastname: Jeong
authors.affiliation: Department of Food Science and Technology, Seoul Women's University, Seoul, Republic of Korea.
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Choi
mesh_terms: D000284:Administration, Oral; D000818:Animals; D005243:Feces / Q000737:chemistry; D005260:Female; D007700:Kinetics; D008297:Male; D053758:Nanoparticles / Q000008:administration & dosage / Q000032:analysis / Q000737:chemistry; D010316:Particle Size; D051381:Rats; D012822:Silicon Dioxide / Q000008:administration & dosage / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics; D014018:Tissue Distribution
chemical_list: D012822:Silicon Dioxide
keywords: biological fate; size effect; target organ