A new type of boron-rich, DSPC-free, unilamellar liposomes was formed using the novel dual-chain, ionic, nido-carborane lipid, K[nido-7-(C16H33OCH2)2CHOCH2-7,8-C2B9H11] (DAC-16), and cholesterol for encapsulation of an aqueous buffer core. Since DSPC was not necessary for the formation of stable DAC-16 liposomes, the boron concentration of these vesicles was increased dramatically to approximately 8.8 wt % in the dry lipid; these liposomes had a high bilayer boron incorporation efficiency of 98%. DSPC-free liposomes exhibited a size distribution pattern of 40-60 nm, which was in the range normally associated with selective tumor uptake. This size distribution was maintained throughout storage at room temperature for several months. Additionally, optimized liposome formulations incorporating DAC-16, DSPC, and cholesterol were identified having stable size distribution patterns after storage for more than two months at a variety of temperatures. Although animal studies indicate that DAC-16 liposomes are toxic, this new ionic nido-carborane lipid allows the formation of liposomes of high boron content for in vitro applications that require the delivery of large amounts of boron.

Unique nanosized closomers of high boron content that may exhibit potential as boron neutron capture therapy target species have been synthesized. The design of these boron-rich nanospheres is based in part on previous work involving dodeca(carboranyl)-substituted closomers [Thomas, J.; Hawthorne, M. F. Chem. Commun. 2001, 1884-1885]. Coupling of ortho-carborane moieties through ester and ether linkages to the rigid [closo-B(12)(OH)(12)](2-) scaffold resulted in the development of a 12(12)-closomer-ester derivative, dodeca[6-(1,2-dicarba-closo-dodecaboran-1-yl)hexanoate]-closo-dodecaborate (2-), 6, and 12(12)-closomer-ether derivatives, dodeca[6-(2-methy1-1,2-dicarba-nido-dodecaboran-1-yl)hexyl]-closo-dodecaborane (14-), 14, and dodeca[6-(7,8-dicarba-nido-dodecaboran-7-yl)hexyl]-closo-dodecaborane (14-), 15. These closomers were investigated by UV-visible spectroscopy and cyclic voltammetry. Additionally, a deboronation method employing NaCN as the nucleophilic reagent was utilized to obtain sodium salts of the ether-linked nido-closomer polyanions, which were purified using a newly developed size-exclusion high pressure liquid chromatography method.

No abstract

A series of amphiphilic amine hydrochloride salts of B-polymethylated (camouflaged) (aminoalkyl)- and bis(aminoalkyl)carboranes have been designed and synthesized in high yield for the purpose of constructing novel carborane-based nanomaterials. Due to the distinct separation of the hydrophobic and hydrophilic regions within each salt, the mono- and disubstituted amphiphiles spontaneously self-assembled upon sonication into rod-shape micro/nanostructures in aqueous solutions. The effects of concentration, method of dispersion, solvent, chain length, counterion, ionic charge, and underlying carborane cage structure on the formation of the these rod products were investigated. The microrods have been studied by transmission electron microscopy (TEM), optical microscopy, X-ray powder diffraction (XRD), thermogravimetric/differential thermal analysis (TG/DTA), and FTIR. For the first time, this work clearly demonstrates the self-assembly of B-polymethylated carboranes into supramolecular structures.

No abstract