Folate receptor-targeted liposomes as possible delivery vehicles for boron neutron capture therapy

Background: The folate receptor is amplified in a variety of human tumors including over 90% of ovarian carcinoma. FR-targeted liposomes have previously been used by its to selectively deliver entrapped boron-containing compounds to tumor cells for neutron capture therapy (NCT). In the present study we have evaluated the delivery of Na-3(B20H17NH3), which has been loaded into FR-targeted liposomes, in mice beating xenograft implants of FR (+) KB subcutaneous tumor. Materials and Methods: Na-3(B20H17NH3) was passively entrapped into FR-targeted hposomes, which were administered intravenously into nude mice beating s.c. implants of the FR(+) human oral carcinoma KB cell line. Normal and tumor boron content was measured by direct current plasma-atomic emission spectroscopy. Results: Mice that received FR-targeted liposomes containing boron showed the highest tumor boron levels at 24 hours (61 mug/g) and tumor/blood boron ratios continued to rise for up to 120 hours. Conclusion: Boron delivery via FR-targeted liposomes is feasible and potentially can improve tumor uptake compared to non-targeted liposomes, and may improve cellular and subcellular localization.