Detailed biodistribution of liposomes prepared with polyborane instead of cholesterol for BNCT: effects of PEGylation

Abstract

Various drug delivery systems for boron neutron capture therapy (BNCT) have been developed. To selectively destroy cancer cells, the high accumulation and selective delivery of 10B into tumor tissue are required. In this study, a polyborane for BNCT with enhanced hydrophobicity was synthesized from decaborane as a boron carrier, and embedded into bare and PEGylated liposomes. These liposomes having diameters of 40–43 nm were injected into tail vein of tumor-bearing mice to evaluate their biodistribution. Boron concentrations in tumor and tumor/blood ratios of the liposomes were reached over 30 μg/g of tissue and over 5 at 8–24 h, respectively. At 12 h after injection, PEGylated liposomes were found in tumor with high boron level (130.0 μg/g of tissue). This result showed that the PEGylated liposomes with a diameter of 40 nm were able to achieve efficient intratumoral 10B amount without replacing the 11B with 10B.