Synthesis, liposomal preparation, and in vitro toxicity of two novel dodecaborate cluster lipids for boron neutron capture therapy

• A new class of lipids, contg. 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 neg. charges. Differential scanning calorimetry shows that B-6-14 and B-6-16 bilayers have main phase transition temps. of 18.8 and 37.9 DegC, resp. Above the transition temp. of 18.8 DegC, B-6-14 can form liposomal vesicles, representing the first boron-contg. lipid with this capability. Upon cooling below the transition temp., stiff bilayers are formed. When incorporated into liposomal formulations with equimolar amts. of distearoyl phosphatidylcholine (DSPC) and cholesterol, stable liposomes are obtained. The z-potential measurements indicate that both B-6-14- and B-6-16-contg. vesicles are neg. charged, with the most neg. 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 prepd. 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 prepd. from B-6-16 were not toxic even at 30 mM.

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NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

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Chemistry

Kemi

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