title: [(99m)Tc radiolabeling of a novel polypeptide molecular probe for lung cancer and its biodistribution in animals].
abstract: OBJECTIVE
  To develop a method for (99m)Tc radiolabeling of a small molecular peptide targeting lung carcinoma and observe the biokinetics and biodistribution of the labeled peptide in normal mice and rabbits.
  
  
  METHODS
  MAG3-peptide (cNGQGEQc) was labeled with (99m)Tc and the labeling rate was determined with paper chromatography. In vitro stability test, cysteine challenge test and serum incubation test were performed for radiochemical evaluation of the labeled peptide. Blood (99m)Tc-peptide clearance in rabbits was evaluated by determining blood radioactive concentrations at different time points after injection of 37 MBq (99m)Tc-peptide, and its dynamic distribution was investigated by SPECT imaging. The percent injected dose per gram of tissue was calculated for each organ of mice injected intravenously with 7.4 MBq (99m)Tc-peptide based on gamma counter readings.
  
  
  RESULTS
  The labeling rate of (99m)Tc-peptide exceeded 90%, and the radiochemical purity was 91% after placing for 12 h at room temperature and 85% after incubation at 37 degrees celsius; with human serum. The cysteine replacement rate was less than 7%, and the binding rate of (99m)Tc-peptide with serum proteins was below 5%. SPECT imaging showed that the labeled peptide could be quickly cleared from the blood in normal animals primarily through the kidneys, and the radioactivity in other tissues and organs remained low.
  
  
  CONCLUSIONS
  (99m)Tc-peptide can be easily prepared with a high labeling yield. With good stability both in vitro and in vivo, (99m)Tc-peptide can be quickly cleared from the blood and excreted though the kidney with ideal biodistribution and biokinetics in vivo.
authors.affiliation: Department of Nuclear Medicine, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China. E-mail: ligp62@126.com.
authors.forename: Guiping
authors.initials: G
authors.lastname: Li
authors.forename: Baodan
authors.initials: B
authors.lastname: Huang
authors.forename: Li
authors.initials: L
authors.lastname: DU
authors.forename: Kai
authors.initials: K
authors.lastname: Huang
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000818:Animals; D006801:Humans; D008297:Male; D051379:Mice; D015335:Molecular Probes; D015609:Organotechnetium Compounds / Q000097:blood*; D011817:Rabbits; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D015335:Molecular Probes; D015609:Organotechnetium Compounds