Cancer represents a significant global health challenge due to its uncontrolled cell growth and resistance to conventional therapies. Among innovative treatments, boron neutron capture therapy (BNCT) has emerged as a promising approach. BNCT relies on the selective accumulation of boron-containing agents in tumor cells, which, after neutron irradiation, produce cytotoxic α particles via a nuclear reaction, allowing the destruction of malignant cells while minimizing damage to healthy tissues. However, the clinical success of BNCT faces challenges such as nonspecific biodistribution and rapid metabolism of boron agents and the necessity for a significant number of boron atoms to be localized on or within neoplastic cells. In this study, we explore the use of carriers, specifically apoferritin and β-cyclodextrins, to accumulate boron clusters inside tumor cells. A boron cluster, cobaltabis(dicarbollide) (Cosan) containing 18 boron atoms per molecule was used, and its nanoformulations were tested for the treatment of different types of cancer, including breast cancer, lung cancer, and mesothelioma.

Apoferritin nanohybrids were synthesized by encapsulating Cosan through pH-mediated disassembly at pH=2 and reassembly at physiological pH. Encapsulation efficiency was assessed using Bradford assay and ICP-MS. Uptake studies were performed on different cell lines, with boron content analyzed by ICP-MS. Cell viability and uptake efficiency were evaluated. AB22 mesothelioma cells incubated with free Cosan or Apoferritin nanohybrids were subjected to neutron irradiation, and post-treatment effects were assessed via clonogenic assay. Cyclodextrin adducts were synthesized by incubating at pH 7,4 and 37°C β-cyclodextrin derivatives with Cosan or TLP, a curcumin derivative that includes a Cosan moiety.

A high cargo loading capacity of Apoferritin was achieved, specifically 6,1 ± 1,7 Cosan molecules were effectively encapsulated within the inner cavity of apoferritin. Uptake experiments with AB22 mesothelioma cells showed a significant boron uptake, sufficient for neutron irradiation. For BNCT, AB22 cells incubated with only Cosan or apoferritin nanohybrid were neutron irradiated. Clonogenic assays showed a 50% colony reduction compared to irradiated and untreated controls, highlighting more efficacy of apoferritin for boron delivery for BNCT. Cyclodextrin adducts with Cosan and TLP showed a high affinity of both cyclodextrins, suggesting their potential use as carriers. Additionally, preliminary results indicated a TLP higher toxicity compared to Cosan in lung cancer A549 and LLC cell lines, further supporting its potential as an effective boron delivery system.

We successfully developed an apoferritin nanohybrid and cyclodextrins adducts, which can act as delivery systems that efficiently encapsulates boron-containing molecules for potential use in BNCT.