Capture-Enhanced Neutron Irradiation as a novel strategy for Alzheimer’s Disease treatment

This PhD thesis work was carried out within the framework of the NECTAR project (NEutron Capture-enhanced Treatment of neurotoxic Amyloid aggRegates), funded by the European Innovation Council under the Horizon 2020 FET Open RIA programme. NECTAR project aims to explore the effectiveness of a Capture-Enhanced Neutron Irradiation (CENI) treatment, exploring the role of the neutron capture reactions on 10B and 157Gd in order to depolymerize β-Amyloid aggregates, one of the main culprits of Alzheimer’s Disease (AD). The PhD research combines experimental investigations and computational modelling across multiple scales. Boron-enriched compounds targeting β-Amyloid were synthesised and characterised; among them, Phoenix and Chimera (curcumin derivatives) achieved the highest binding efficiencies (70% and 75%, respectively). “Cell-free” irradiation experiments at the TRIGA Mark II reactor (Pavia) demonstrated substantial fibril density reduction: 50% after irradiations at 250 kW for 1 h and 15 minutes, and up to 75% after 15 minutes at 30 kW. Complementary Monte Carlo simulations with MCNP6 estimated absorbed doses of 35 Gy, 8.7 Gy, and 1.1 Gy under these conditions. In-vitro studies in collaboration with Stockholm University investigated cytotoxicity in HMC3 microglial and SH-SY5Y neuroblastoma cell lines. Phoenix showed concentration-dependent cytotoxicity, reducing viability by 50% at concentrations >8–9 µM after 48 hours. Neutron irradiation further decreased viability for concentrations >4 µM. Interestingly, viability in SH-SY5Y increased by 8% when Phoenix was removed before irradiation at 30 kW, suggesting a possible protective effect. Complementary Geant4 simulations provided detailed microdosimetric insight, indicating that significant contributions to local dose arise at lineal energy values above 100 keV/µm, mostly from secondary particles generated by 10B neutron capture. At in-vivo scale, a dedicated irradiation set-up using a lithium carbonate shield enriched to 95% in 6Li was developed, reducing gamma background by 70% compared to BNCT standard protocols. This shield was used during in-vivo treatment on wild type mice models, irradiated with a total equivalent dose of 5 Gy imparted to the brain. Post-irradiation analyses conducted up to one month confirmed the absence of adverse effects, supporting the safety of the proposed CENI treatment. Additionally, a voxel-based mouse model was developed to enable anatomically resolved dosimetric assessments. Finally, the thesis advances toward CENI clinical application by developing and testing a prototype Beam Shaping Assembly (BSA) at the HF-ADNeF facility in order to obtain a low-energy neutron beam. The constructed BSA was built with a FluentalTM moderator and a half-lead, half-graphite reflector, achieving an epithermal neutron flux of 1.9·109 n cm-2 s-1. Further computational optimisations explored alternative configurations using lead reflectors and AlF3 or MgF2 moderators to reduce the epithermal flux and improve the BSA performance (lower thermal and fast neutron and gamma contaminations). Overall, this work presents the first proof-of-concept of a possible CENI treatment for AD, demonstrating feasibility and safety. These findings establish a robust basis for future studies to confirm therapeutic efficacy and explore applications targeting other pathological proteins, such as tau and α-synuclein, implicated in neurodegenerative diseases.