title: Optical imaging of absorption and distribution of RITC-SiO2 nanoparticles after oral administration.
abstract: OBJECTIVE
  In this study, we investigated the absorption and distribution of rhodamine B isothiocyanate (RITC)-incorporated silica oxide nanoparticles(SiNPs) (RITC-SiNPs) after oral exposure, by conducting optical imaging, with a focus on tracking the movement of RITC-SiNPs of different particle size and surface charge.
  
  
  METHODS
  RITC-SiNPs (20 or 100 nm; positively or negatively charged) were used to avoid the dissociation of a fluorescent dye from nanoparticles via spontaneous or enzyme-catalyzed reactions in vivo. The changes in the nanoparticle sizes and shapes were investigated in an HCl solution for 6 hours. RITC-SiNPs were orally administered to healthy nude mice at a dose of 100 mg/kg. Optical imaging studies were performed at 2, 4, and 6 hours after oral administration. The mice were sacrificed at 2, 4, 6, and 10 hours post-administration, and ex vivo imaging studies were performed.
  
  
  RESULTS
  The RITC-SiNPs were stable in the HCl solution for 6 hours, without dissociation of RITC from the nanoparticles and without changes in size and shape. RITC-SiNPs flowed into the small intestine from the stomach and gradually moved along the gut during the experiment. In the ex vivo imaging studies, optical signals were observed mostly in the lungs, liver, pancreas, and kidneys. The orally administered RITC-SiNPs, which were absorbed in the systemic circulation, were eliminated from the body into the urine. The 20 nm RITC-SiNPs showed higher uptake in the lungs than the 100 nm RITC-SiNPs. The distribution of the 100 nm RITC-SiNPs in the liver was higher than that of the 20 nm RITC-SiNPs, but the differences in the surface charge behavior were imperceptible.
  
  
  CONCLUSIONS
  We demonstrated that the movement of RITC-SiNPs after oral exposure could be traced by optical imaging. Optical imaging has the potential to provide valuable information that will help in understanding the behavior of SiNPs in the body following exposure.
authors.affiliation: Department of Biomedical Engineering, Chonnam National University, Yeosu, Jeollanam-Do, Republic of Korea.
authors.forename: Chang-Moon
authors.initials: CM
authors.lastname: Lee
authors.affiliation: Department of Nuclear Medicine, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Cyclotron Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Biomedical Research Institute, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea.
authors.forename: Tai Kyoung
authors.initials: TK
authors.lastname: Lee
authors.affiliation: Department of Biomedical Engineering, Chonnam National University, Yeosu, Jeollanam-Do, Republic of Korea ; School of Electrical, Electronic Communication, and Computer Engineering, Chonnam National University, Yeosu, Jeollanam-Do, Republic of Korea.
authors.forename: Dae-Ik
authors.initials: DI
authors.lastname: Kim
authors.affiliation: Department of Biochemistry and Molecular Biology, Korea University Medical School and College, Seounbuk-Gu, 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, Seounbuk-Gu, Seoul, Republic of Korea.
authors.forename: Meyoung-Kon
authors.initials: MK
authors.lastname: Kim
authors.affiliation: Department of Nuclear Medicine, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Cyclotron Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Biomedical Research Institute, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea.
authors.forename: Hwan-Jeong
authors.initials: HJ
authors.lastname: Jeong
authors.affiliation: Department of Nuclear Medicine, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Cyclotron Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Biomedical Research Institute, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea.
authors.forename: Myung-Hee
authors.initials: MH
authors.lastname: Sohn
authors.affiliation: Department of Nuclear Medicine, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Cyclotron Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Biomedical Research Institute, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea ; Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeollabuk-Do, Republic of Korea.
authors.forename: Seok Tae
authors.initials: ST
authors.lastname: Lim
mesh_terms: D000284:Administration, Oral; D000818:Animals; D005456:Fluorescent Dyes / Q000737:chemistry / Q000493:pharmacokinetics; D051379:Mice; D008819:Mice, Nude; D053758:Nanoparticles / Q000737:chemistry; D061848:Optical Imaging / Q000379:methods*; D012235:Rhodamines / Q000737:chemistry / Q000493:pharmacokinetics; D012822:Silicon Dioxide / Q000737:chemistry / Q000493:pharmacokinetics; D014018:Tissue Distribution
chemical_list: D005456:Fluorescent Dyes; D012235:Rhodamines; D012822:Silicon Dioxide; C027755:rhodamine isothiocyanate
keywords: RITC-SiNP; oral exposure; rhodamine B isothiocyanate; silica nanoparticles