Determination of liposomal boron biodistribution in tumor bearing mice by using neutron capture autoradiography

It is necessary to accumulate the 10B atoms selectively to the tumor cells for effective boron neutron capture therapy (BNCT). In order to achieve accurate measurements of 10B concentrations in biological samples, we employ a technique of neutron capture autoradiography (NCAR) of the sliced whole body samples of tumor bearing mice using CR- 39 plastic track detectors. The CR-39 detectors attached with samples were exposed to thermal neutrons in the thermal column of the TRIGA II reactor at the Institute for Atomic Energy, Rikkyo University. We obtained NCAR images for mice injected intraveneously by 10B-polyethylene-glycol (PEG) binding liposome or 10B-bare liposome. The 10B concentrations in the tumor tissue of mice were estimated by means of alpha and lithium track density measurements. In this study, we increased the accumulation of 10B atoms in the tumor tissues by binding PEG chains to the surface of liposome, which increase the retension in the blood flow and escape the phagocytosis by reticulo-endotherial systems. Therefore, 10B-PEG liposome is a candidate for an effective 10B carrier in BNCT.(author)