Characterisation of the TAPIRO BNCT thermal facility

A novel10B-enriched carboranyl-containing phthalocyanine as a radio- and photo-sensitising agent for boron neutron capture therapy and photodynamic therapy of tumours: in vitro and in vivo studies

The synthesis of a Zn(ii)-phthalocyanine derivative bearing four 10B-enriched o-carboranyl units (10B-ZnB4Pc) and its natural isotopic abundance analogue (ZnB4Pc) in the peripheral positions of the tetraazaisoindole macrocycle is presented. The photophysical properties of ZnB4Pc, as tested against model biological systems, were found to be similar with those typical of other photodynamically active porphyrin-type photosensitisers, including a singlet oxygen quantum yield of 0.67. The carboranyl-carrying phthalocyanine was efficiently accumulated by B16F1 melanotic melanoma cells in vitro, appeared to be partitioned in at least some subcellular organelles and, upon red light irradiation, induced extensive cell mortality. Moreover, ZnB4Pc, once i.v.-injected to C57BL/6 mice bearing a subcutaneously transplanted pigmented melanoma, photosensitised an important tumour response, provided that the irradiation at 600-700 nm was performed 3 h after the phthalocyanine administration, when appreciable concentrations of ZnB4Pc were still present in the serum. Analogously, irradiation of the 10B-ZnB4Pc-loaded pigmented melanoma with thermal neutrons 24 h after injection led to a 4 day delay in tumour growth as compared with control untreated mice. These results open the possibility to use one chemical compound as both a photosensitising and a radiosensitising agent for the treatment of tumours by the combined application of photodynamic therapy and boron neutron capture therapy.

Characterisation of the TAPIRO BNCT epithermal facility

A collimated epithermal beam for boron neutron capture therapy (BNCT) research has been designed and built at the TAPIRO fast research reactor. A complete experimental characterisation of the radiation field in the irradiation chamber has been performed, to verify agreement with IAEA requirements. Slow neutron fluxes have been measured by means of an activation technique and with thermoluminescent detectors (TLDs). The fast neutron dose has been determined with gel dosemeters, while the fast neutron spectrum has been acquired by means of a neutron spectrometer based on superheated drop detectors. The gamma-dose has been measured with gel dosemeters and TLDs. For an independent verification of the experimental results, fluxes, doses and neutron spectra have been calculated with Monte Carlo simulations using the codes MCNP4B and MCNPX_2.1.5 with the direct statistical approach (DSA). The results obtained confirm that the epithermal beams achievable at TAPIRO are of suitable quality for BNCT purposes.