БНЗТ-2019

Experimental evaluation of the intracranial way of administration of boron compounds for subsequent BNCT.

Not scheduled

15m

Academpark

Speakers

Mrs Anna Kasatova (Novosibirsk State University) Mr Nikita Filin (Novosibirsk State University) Mr Roman Sibirtsev (Novosibirsk State University)

Description

Boron neutron capture therapy is a treatment for malignant tumors, both primary and recurrent. Most clinical trials have been conducted in patients with glioblastoma, which are aggressive and resistant to standard treatment of brain tumors. For the best implementation of the method of boron neutron capture therapy, targeted delivery agents, containing a sufficient number of boron-10 atoms are needed. However, due to the presence of the blood-brain barrier (BBB), many substances cannot penetrate the brain and accumulate in the tumor in concentration sufficient to carry out the therapy. Liposomal compositions having boron in their structure are promising for boron neutron capture therapy of glioblastoma. This study is focused on the possibility of delivering boron compounds, avoiding BBB, directly into the cerebrospinal fluid spaces of the brain and assessing the dynamics of its accumulation in its various structures. **Purpose:** To investigate the possibility of introduction of boron-containing liposomes with a fluorescent label into cisterna magna for BNCT in a rat model. **Goals:** 1. To evaluate the reaction of the animal to the introduction of liposomal structures containing Nile red and sodium borocaptate in cisterna magna of rat’s brain. 2. To assess the accumulation of boron by ICP AES analysis and Nile red dye assignment by fluorescence microscopy in the brain tissue of the animals. 3. To carry out comparative analysis of the data to develop methods for target delivery of boron compounds in brain tumors. **Materials and methods:** The study was performed on 6 male Norway rats (Rattus norvegicus) (Institute of Cytology and Genetics SB RAS), at the age of 12 weeks, average weight of about 500 g. Each animal was anesthetized (intraperitoneally, Domitor 0.1% and Zoletil 99.9%), a stereotactic apparatus was inserted and butterfly catheters G23 introduced into cisterna magna with subsequent aspiration of cerebrospinal liquid in a volume of 300 - 450 μl. The injection of liposomes with sodium borocaptate (BSH) and Nile red was carried out in a volume of 150 - 200 μl, with a concentration of boron in the initial solution of 5800 ppm, control group was injected with 0.9% sodium chloride solution in a volume of 200 ml. The average size of liposomes was 100 nm. After the manipulations, the reaction of the animal was monitored, the planned euthanasia was carried out 1 hour, 2 hours, 3 hours after drug administration. The autopsy brain was removed, washed in PBS onces, and divided into two hemispheres in the sagittal plane. The first hemisphere was used to prepare histological slices and investigation of the distribution of Nile red in different structures of the brain using a fluorescence microscope (Carl Zeiss). For ICP AES second hemisphere was divided into 5 parts: brainstem, cerebellum, subcortical nuclei, temporoparietal lobe, frontal lobe, packed in separate plastic bags and stored at a temperature of -20 ° C, following sample preparation was done using acid digestion [А. Tsygankova at al. RAP Conference Proceedings, 2019]. Sample analysis was performed on an iCAP-6500 spectrometer (Thermo). **Results and discussion:** During the experiment, 4 animals out of 6 died earlier than it was planned for euthanasia in the interval 20-40 minutes after injection. Despite the evacuation of cerebrospinal fluid and a decrease of intracranial pressure, respiratory arrest occurred. The same way of administration of NaCl saline, no lethal outcomes were observed. A possible cause of death of animals is the toxic effect of liposome compositions containing boron-10 and Nile red compounds. As a result of the ICP AES, a higher concentration of boron-10 was measured in cerebellum and was 81.8 μg10В/g 20 minutes after injection, 60.2 μg10В/g 40 minutes and 13.6 μg10В/g 3 hours after the injection of the drug, but only 1.8 μg10В/g per point 2 hours. The next section of the brain with high boron accumulate was in the stem: it was found that 48.6 μg10В/g, 26.1 μg10В/g, 2 μg10В/g and 7 μg10В/g at the time points of 20 minutes, 40 minutes, 2 and 3 hours, respectively. The concentration of boron in the subcortical nuclei was 43.2, 14.2, 1 and 4.9 μg10В/g after 20, 40 minutes, 2 and 3 hours after the introduction of liposomes. The lowest concentration of boron-10 was detected in the frontal lobe and was 20.2 μg10В/g at time point of 20 minutes, 5.4 at time point of 40 minutes 0.83 and 2 μg10В/g at point of 2 and 3 hours, respectively; for the parietal and temporal lobes - 34 μg10В/g, 17.2 μg10В/g, 0.83 μg10В/g and 2 μg10В/g after 20 minutes, 40 minutes, 2 and 3 hours after application, respectively. Probably, the differences in distribution of boron in various structures of the brain are due to diffuse processes and the movement of cerebrospinal fluid. **Conclusion:** The obtained data showed that the direct injection pathway of liposomes into the cisterna magna of the rat brain can be one of the ways of boron 10 delivery to different parts of the brain for BNCT. The study was supported by a grant from the Russian Science Foundation (project No. 19-72-30005) using the equipment of the Center for Laboratory Animal Genetic Resources of the Federal Center for Science and Technology of the Siberian Branch of the Russian Academy of Sciences, supported by the Russian Ministry of Science and Science (Unique project identifier RFMEFI62117X0015).

Summary

Perspective method of boron drug delivery to the tumor cells by means of liposomal compositions can be used in Boron Neutron Capture Therapy (BNCT) for treatment of malignant brain tumors. In present pilot study intracranial pathway was used to determine how boron is distributed and accumulated in normal brain avoiding blood-brain barrier.
Norway rats (Rattus norvegicus) were anesthetized, a catheter was stereotactically introduced into cisterna magna, the volume 300-450 ml of cerebrospinal fluid was aspirated, and the drug was administered. after 1, 2, 3 hours the planned euthanasia and brain autopsy were performed. Evaluation of boron concentration was performed using ICP AES (inductively coupled plasma atomic emission spectrometry) analysis. Distribution of Nile red in brain tissue was visualized by means of fluorescent microscopy.