Water-soluble carboranyl-phthalocyanines for BNCT. Synthesis, characterization, and in vitro tests of the Zn(ii)-nido-carboranyl-hexylthiophthalocyanine

Daniela Pietrangeli, Angela Rosa, Antonietta Pepe, Saverio Altieri, Silva Bortolussi, Ian Postuma, Nicoletta Protti, Cinzia Ferrari, Laura Cansolino, Anna Maria Clerici, Elisa Viola, Maria Pia Donzello, Giampaolo Ricciardi

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Abstract

The zinc(ii) complex of the octa-anionic 2,3,9,10,16,17,23,24-octakis-(7-methyl-7,8-dicarba-nido-undeca-boran-8-yl)hexyl-thio-6,13,20,27-phthalocyanine (nido-[ZnMCHESPc]Cs8, 7) has been obtained in the form of caesium salt through mild deboronation of the neutral precursor, the closo-[ZnMCHESPc] complex, 6, with CsF. 6 has been synthesized, in turn, by heating a finely ground mixture of the appropriate phthalonitrile and zinc(ii) acetate at 180.0 °C. The complexes have been characterized by elemental analyses, FT-IR, UV-visible absorption and fluorescence emission spectroscopy, and their structures were assessed by 1H, 13C, 11B, and two-dimensional homo- and hetero-correlated NMR spectroscopy experiments. 7 showed appreciable solubility in water solution, together with a marked tendency to aggregate. Aggregation of 7 in the hydrotropic medium resulted in significant fluorescence quenching. Instead, fluorescence quantum yields (ΦF) of 0.14 and 0.08, and singlet oxygen quantum yields (ΦΔ) of 0.63 and 0.24 were obtained for 6 and 7, respectively, in a DMF solution. In vitro boron neutron capture therapy (BNCT) experiments, employing boron imaging techniques as implemented in qualitative and quantitative neutron autoradiography methods, showed that 7 is capable of increasing the boron concentration of two selected cancerous cell lines, the DHD/K12/TRb of rat colon adenocarcinoma and UMR-106 of rat osteosarcoma, with the large-size Cs+ counter-ions used to neutralize the negatively charged carborane polyhedra not presenting a significant obstacle to the process. Taken together, BNCT and photophysical measurement results indicated that 7 is potentially suitable for bimodal or multimodal anticancer therapy.

Original languageEnglish
Pages (from-to)11021-11028
Number of pages8
JournalDalton Transactions
Volume44
Issue number24
DOIs
Publication statusPublished - Jun 28 2015

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ASJC Scopus subject areas

  • Inorganic Chemistry

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Pietrangeli, D., Rosa, A., Pepe, A., Altieri, S., Bortolussi, S., Postuma, I., Protti, N., Ferrari, C., Cansolino, L., Clerici, A. M., Viola, E., Donzello, M. P., & Ricciardi, G. (2015). Water-soluble carboranyl-phthalocyanines for BNCT. Synthesis, characterization, and in vitro tests of the Zn(ii)-nido-carboranyl-hexylthiophthalocyanine. Dalton Transactions, 44(24), 11021-11028. https://doi.org/10.1039/c5dt00394f