Recently, exploitation of cerebrospinal fluid (CSF) circulation has become increasingly recognized as a feasible strategy to solve the challenges involved in drug delivery for treating brain tumors. Boron neutron capture therapy (BNCT) also faces challenges associated with the development of an efficient delivery system for boron, especially to brain tumors. Our laboratory has been developing a system for boron delivery to brain cells using CSF, which we call the “boron CSF administration method”. In our previous study, we found that boron was efficiently delivered to the brain cells of normal rats in the form of small amounts of L-p-boronophenylalanine (BPA) using the CSF administration method. In the study described here, we carried out experiments with brain tumor model rats to demonstrate the usefulness of the CSF administration method for BNCT. We first investigated the boron concentration of the brain cells every 60 min after BPA administration into the lateral ventricle of normal rats. Second, we measured and compared the boron concentration in the melanoma model rats after administering boron via either the CSF administration method or the intravenous (IV) administration method, with estimation of the T/N ratio. Our results revealed that boron injected by the CSF administration method was excreted quickly from normal cells, resulting in a high T/N ratio compared to that of IV administration. In addition, the CSF administration method resulted in high boron accumulation in tumor cells. In conclusion, we found that using our developed CSF administration method results in more selective delivery of boron to the brain tumor compared with the IV administration method.

In the boiler feed-water system of thermal power plants, iron oxide scale is generated due to the corrosion of piping, which decreases the effectiveness of the heat exchanger in the boiler and contributes to reduced power generation efficiency. Scale removal can prevent this phenomenon, which consequently results in decreased carbon dioxide emission. In a previous study, an iron scale removal system was developed using superconducting magnets, and high-gradient magnetic separation (HGMS) experiments were conducted using the height difference between the inflow and outflow tanks. As a result, particles were intensively captured by the filters at the inflow side. We succeeded in eliminating this capture by properly controlling the applied magnetic field. However, because the suspension also flowed due to the height difference in this experiment, the problems of partial blockage of the filter and the resulting decrease in the flow rate were not resolved even under the controlled magnetic field. In this study, HGMS experiments were conducted under a constant flow rate with a large pump in a large-scale system having a filter diameter of 300 mm to simulate a boiler feed-water system or chemical cleaning line. Furthermore, we investigated the feasibility of the large-scale HGMS system and elucidated the scale-up effect on the amount captured and the spatial distribution of the captured particles on the filters. Based on these results, a plant-scale HGMS system (800 mm filter diameter) was designed.