title: Direct labelling of octreotide with 99mTc: effect of different concentration of reducing agents and amount of sodium pertechnetate on radiolabelling efficiency.
abstract: Octreotide, a synthetic analog of natural hormone somatostatin, was labelled with 99mTc. Labelling was accomplished by reduction of the cysteine bridge, which provided sulfhydryl groups for chelating with 99mTc. Sodium ascorbate and sodium dithionite in different concentrations were used as reducing agents. Different amounts of sodium pertechnetate were used for labelling of peptide. When the mass ratio of peptide and sodium ascorbate was 1:100 and the final concentration of dithionite in the labelling vial was 0.2-0.4 microg/microl with 0.18-1.48 GBq sodium pertechnetate more than 80% radiolabelling efficiency was confirmed by RP-HPLC, ITLC-SG and C18 Cartridge analysis. The stability of the 99mTc-peptide bond was evaluated by human serum challenge and that showed the stability was 90% after 4h.
authors.affiliation: Radioisotope Division, Nuclear Research Center, Atomic Energy Organization of Iran, Tehran, Iran. rnajafi@seai.neda.net.ir
authors.forename: M
authors.initials: M
authors.lastname: Gandomkar
authors.forename: R
authors.initials: R
authors.lastname: Najafi
authors.forename: S E
authors.initials: SE
authors.lastname: Sadat Ebrahimi
authors.forename: A
authors.initials: A
authors.lastname: Shafiee
authors.forename: M H
authors.initials: MH
authors.lastname: Babaei
authors.forename: M
authors.initials: M
authors.lastname: Rabbani
authors.forename: G A
authors.initials: GA
authors.lastname: Shabani
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D015282:Octreotide / Q000737:chemistry*; D015609:Organotechnetium Compounds / Q000737:chemistry*; D019163:Reducing Agents / Q000737:chemistry*; D013670:Sodium Pertechnetate Tc 99m / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D015609:Organotechnetium Compounds; D019163:Reducing Agents; D013670:Sodium Pertechnetate Tc 99m; D015282:Octreotide