Buckysomes: New Nanocarriers for Anticancer Drugs

Buckysomes, liposome-like vesicles comprised of dendritic C60 subunits that self-assemble into unilamellar vesicles, are unique nanovectors that have utility in drug delivery. We have prepared paclitaxel-embedded buckysomes (PEBs) and examined biodistriubition profiles with commercially available formulations of the drug. As compared to Abraxane, an albumin-bound formulation of paclitaxel, PEBs showed higher tissue accumulation in the liver and the kidney at 45 and 60 minutes and in the lungs at 30 minutes, making them suitable drug-delivery carriers for short-term therapy to the mentioned organs. These buckysomes can be further functionalized to specifically deliver paclitaxel to the tumor site. 1. Introduction Paclitaxel is a very potent anticancer drug that has been used since 1967 to treat breast, ovarian, and lung cancer, as well as advanced forms of Kaposi’s sarcoma [1]. Paclitaxel is a hydrophobic drug (solubility ~0.3？μg/mL) [2] that was previously administered via dissolution in Cremophor EL (polyoxyethylated castor oil) and dehydrated alcohol. However, the castor oil proved to be toxic [3, 4], so other alternatives for paclitaxel delivery were investigated, such as the use of nanoscale carrier vectors [2, 5, 6]. Among the different types of nanocarriers, liposomes have received a lot of attention and have proven to be very good carriers of drugs and/or contrast agents [7]. Paclitaxel-embedded buckysomes have the potential for delivering the hydrophobic drug directly to tumor sites. The buckysomes are self-assembled structures of the monomer AF-1, a modified water soluble fullerene that contains 18 carboxylic acid groups and 5 didodecyl malonate chains around the C60 fullerene (Figure 1). This unique functionalization permits the creation of buckysome structures that might offer advantages over traditional phospholipid liposomes as nanovectors. The buckysomes are formulated so they have a dense hydrophobic region, making them ideal for embedding hydrophobic molecules, such as paclitaxel. Liposomes are mostly suitable for carrying a hydrophilic payload in their hydrophilic compartment and less suitable for hydrophobic materials. Another advantage of using buckysomes is the lack of organic solvents during their formation steps as well as their ease of preparation. Figure 1: Chemical structure of the amphiphilic fullerene monomer AF-1. AF-1 has a molecular weight of 5022, a length of 3.5？nm, and a width of 2.3？nm. Previous studies in our group report the synthesis and characterization of buckysome nanovectors for hydrophobic molecule delivery [8].