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

ABSTRACT

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 us 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 Na3(B20H17NH3), which has been loaded into FR-targeted liposomes, in mice bearing xenograft implants of FR (+) KB subcutaneous tumor. MATERIALS AND METHODS: Na3(B20H17NH3) was passively entrapped into FR-targeted liposomes, which were administered intravenously into nude mice bearing 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 (6.1 micrograms/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.