In vitro delivery of borocaptate ions to U87 glioma cells via silk fibroin nanoparticles for boron neutron capture therapy

Boron neutron capture therapy (BNCT) is an oncological treatment based on the neutron capture reaction on 10B. The only two compounds approved for phase I/II clinical trials are sodium borocaptate (BSH) and 4-boronophenylalanine (BPA). While BPA has been widely exploited in clinical trials, the use of BSH is limited due to its insufficient uptake by tumor cells. Herein, we report a novel formulation based on silk fibroin nanoparticles (SFNs), capable of loading a large amount of borocaptate ions. The nanoparticles have been characterized and tested on U87 glioma cells, and boron uptake was measured using neutron autoradiography, which involved irradiating the samples in a thermal neutron field. Measurements demonstrated the crucial role of the nanocarrier in enhancing boron internalization. Notably, SFNs-BSH achieved 29.5 ppm total boron uptake in U87 cells – comparable to clinical BPA – at 4 lower dose.