title: A novel liposome radiolabeling method using 99mTc-"SNS/S" complexes: in vitro and in vivo evaluation.
abstract: Liposomes are important carriers for controlled drug release, for gene or antisense therapy, and for immunization. Radiolabeled liposomes can be used to evaluate the in vivo behavior of different liposome formulations, as well as for diagnostic imaging and radionuclide therapy. A novel method for radiolabeling liposomes with (99m)Tc-"SNS/S" complexes is introduced. This labeling method can be applied to liposome radiolabeling with not only (99m)Tc but also two therapeutic radionuclides, (186)Re and (188)Re. Liposomes encapsulating glutathione (GSH) were studied for (99m)Tc labeling. N,N-bis(2-mercaptoethyl)-N',N'-diethyl-ethylenediamine (BMEDA), N,N-bis(2-mercaptoethyl)-1-butylamine (BMBuA), and benzene thiol (BT) were investigated to make (99m)Tc-"BMEDA", (99m)Tc-"BMEDA + BT", (99m)Tc-"BMBuA", and (99m)Tc-"BMBuA + BT", for liposome labeling. The labeling efficiencies of (99m)Tc-GSH liposomes were from 36.9 to 69.2%. After incubation in serum, (99m)Tc-GSH liposomes labeled with (99m)Tc-"BMEDA" or (99m)Tc-"BMEDA + BT" had the best labeling stability of the formulations tested. Distribution studies after intravenous injection of (99m)Tc-liposomes composed of distearoyl phosphatidylcholine (DSPC) and cholesterol had a slow blood clearance and a high spleen accumulation demonstrating the in vivo labeling stability of the radiolabeled liposomes. The (99m)Tc-liposomes have great potential as a radiopharmaceutical system for evaluating various kinds of liposomes with different lipid composition, for evaluating in advance a subsequent radionuclide therapy using (186)Re or (188)Re labeled liposomes and for diagnostic imaging.
authors.affiliation: Department of Radiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA. bao@uthscsa.edu
authors.forename: Ande
authors.initials: A
authors.lastname: Bao
authors.forename: Beth
authors.initials: B
authors.lastname: Goins
authors.forename: Robert
authors.initials: R
authors.lastname: Klipper
authors.forename: George
authors.initials: G
authors.lastname: Negrete
authors.forename: Mathew
authors.initials: M
authors.lastname: Mahindaratne
authors.forename: William T
authors.initials: WT
authors.lastname: Phillips
mesh_terms: D000818:Animals; D003952:Diagnostic Imaging / Q000379:methods; D004355:Drug Stability; D005978:Glutathione / Q000737:chemistry / Q000378:metabolism; D066298:In Vitro Techniques; D007553:Isotope Labeling / Q000379:methods; D008024:Ligands; D008081:Liposomes / Q000737:chemistry*; D008297:Male; D009942:Organometallic Compounds / Q000097:blood / Q000737:chemistry* / Q000493:pharmacokinetics; D011868:Radioisotopes / Q000737:chemistry*; D019275:Radiopharmaceuticals / Q000097:blood / Q000138:chemical synthesis / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012211:Rhenium / Q000737:chemistry*; D013667:Technetium / Q000737:chemistry*; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D008024:Ligands; D008081:Liposomes; D009942:Organometallic Compounds; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D012211:Rhenium; D013667:Technetium; D005978:Glutathione