title: [IgG radiolabelling with (99m)Tc by tricarbonyl method and its biodistribution in mice].
abstract: OBJECTIVE
  To synthesize the complex fac-[⁹⁹(m)Tc(CO)₃(H₂O)₃](+) for labeling IgG and investigate the in vitro stability of ⁹⁹(m)Tc(CO)₃(H₂O)₃-IgG and its biodistribution in mice.
  
  
  METHODS
  fac-[⁹⁹(m)Tc(CO)₃(H₂O)₃](+) was synthesized and its radiochemical purity determined using polyamide membrane chromatography. IgG was directly labeled with fac-[⁹⁹(m)Tc(CO)₃(H₂O)₃](+) and the labeling ratio was determined using chromatography. The stability of ⁹⁹(m)Tc(CO)₃(H₂O)₃-IgG in human serum albumin and normal saline was evaluated. ⁹⁹(m)Tc(CO)₃(H₂O)₃-IgG was injected via the tail vein into 9 mice at the dose of 3.7×10⁴ Bq/100 µl, and SPECT image was obtained at 2, 4 and 12 h after the injection. The mice were sacrificed at these time points to measure the radioactivity and calculate the %ID/g in each organ.
  
  
  RESULTS
  Fac-[⁹⁹(m)Tc(CO)₃(H₂O)₃](+) had a radiochemical purity of 82.48% and remained stable in vitro at room temperature within 4 h. The labeling ratio of ⁹⁹(m)Tc(CO)₃(H₂O)₃-IgG was 57.04% with a radiochemical purity exceeding 90%. In the solution of human serum albumin, the labeled IgG maintained a stable radiochemical purity, but in normal saline, its radiochemical purity was lowered to 20% at 24 h. After injection in mice, the labeled IgG was deposited mainly in the liver, spleen, kidneys, and the blood pool showed a sustained radioactivity.
  
  
  CONCLUSIONS
  ⁹⁹(m)Tc(CO)₃(H₂O)₃-IgG prepared in this study has good stability in vitro and in vivo in 24 h and shows a biodistribution pattern similar to that of IgG protein in vivo. The intermediate fac-[⁹⁹(m)Tc(CO)₃(H₂O)₃](+) can meet the experimental requirement for labeling monoclonal antibodies and polypeptides.
authors.affiliation: Department of Nuclear Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, China. hua1031@fimmu.com
authors.forename: Xiao-hua
authors.initials: XH
authors.lastname: Chi
authors.forename: Bao-dan
authors.initials: BD
authors.lastname: Huang
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.forename: Kai
authors.initials: K
authors.lastname: Huang
authors.forename: Gui-ping
authors.initials: GP
authors.lastname: Li
mesh_terms: D000818:Animals; D007074:Immunoglobulin G / Q000008:administration & dosage / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: D007074:Immunoglobulin G; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals