This innovation enhances the safety and efficacy of Boron Neutron Capture Therapy (BNCT), a precision treatment for solid tumours that destroys cancer cells while sparing healthy tissue. A modular nanoparticle platform using ultra-small elemental boron cores wrapped in protein shells and encapsulated within targeted liposomes, achieves higher tumour selectivity and sustained intratumoural boron levels. The outcome is effective dosing with lower systemic exposure and smaller drug quantities, paving the way for more affordable, accessible cancer care