Carborane Derivatives Loaded into Liposomes as Efficient Delivery Systems for Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is an anticancer therapy based on the incorporation of 10B in tumors, followed by neutron irradiation. Recently, the synthesis and delivery of new boronated compounds have been recognized as some of the main challenges in BNCT application. Here, we report on the use of liposomes as carriers for BNCT active compounds. Two carborane derivatives, i.e., o-closocarboranyl β-lactoside (LCOB) and 1-methyl-o-closocarboranyl-2-hexylthioporphyrazine (H2PzCOB), were loaded into liposomes bearing different surface charges. The efficacy of these formulations was tested on model cell cultures, that is, DHD/K12/TRb rat colon carcinoma and B16-F10 murine melanoma. These induce liver and lung metastases, respectively, and are used to study the uptake of standard BNCT drugs, including borophenylalanine (BPA). Boron concentration in treated cells was measured by α spectrometry at the TRIGA mark II reactor (University of Pavia). Results showed high performance of the proposed formulations. In particular, the use of cationic liposomes increased the cellular concentration of 10B by at least 30 times more than that achieved by BPA.