title: Synthesis, liposomal preparation, and in vitro toxicity of two novel dodecaborate cluster lipids for boron neutron capture therapy.
abstract: A new class of lipids, containing the closo-dodecaborate cluster, has been synthesized. Two lipids, S-(N, N-(2-dimyristoyloxyethyl)acetamido)thioundecahydro-closo-dodecaborate (2-) (B-6-14) and S-(N, N-(2-dipalmitoyloxyethyl)acetamido)thioundecahydro-closo-dodecaborate (2-) (B-6-16) are described. Both of them have a double-tailed lipophilic part and a headgroup carrying two negative charges. Differential scanning calorimetry shows that B-6-14 and B-6-16 bilayers have main phase transition temperatures of 18.8 and 37.9 degrees C, respectively. Above the transition temperature of 18.8 degrees C, B-6-14 can form liposomal vesicles, representing the first boron-containing lipid with this capability. Upon cooling below the transition temperature, stiff bilayers are formed. When incorporated into liposomal formulations with equimolar amounts of distearoyl phosphatidylcholine (DSPC) and cholesterol, stable liposomes are obtained. The zeta-potential measurements indicate that both B-6-14- and B-6-16-containing vesicles are negatively charged, with the most negative potential described of any liposome so far. The liposomes are of high potential value as transporters of boron to tumor cells in treatments based on boron neutron capture therapy (BNCT). Liposomes prepared from B-6-14 were slightly less toxic in V79 Chinese hamster cells (IC50 5.6 mM) than unformulated Na2B12H11SH (IC50 3.9 mM), while liposomes prepared from B-6-16 were not toxic even at 30 mM.
authors.affiliation: Department of Chemistry, University of Bremen, D-28334 Bremen.
authors.forename: Eugen
authors.initials: E
authors.lastname: Justus
authors.forename: Doaa
authors.initials: D
authors.lastname: Awad
authors.forename: Michaela
authors.initials: M
authors.lastname: Hohnholt
authors.forename: Tanja
authors.initials: T
authors.lastname: Schaffran
authors.forename: Katarina
authors.initials: K
authors.lastname: Edwards
authors.forename: Göran
authors.initials: G
authors.lastname: Karlsson
authors.forename: Luminita
authors.initials: L
authors.lastname: Damian
authors.forename: Detlef
authors.initials: D
authors.lastname: Gabel
mesh_terms: D000818:Animals; D001896:Boron Compounds / Q000737:chemistry / Q000633:toxicity*; D016754:Boron Neutron Capture Therapy; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D008055:Lipids / Q000138:chemical synthesis / Q000633:toxicity*; D008081:Liposomes / Q000737:chemistry / Q000633:toxicity*
chemical_list: D001896:Boron Compounds; D008055:Lipids; D008081:Liposomes; C119788:dodecaborate