RESUMO
Potential boron neutron capture therapy (BNCT) agents have been designed on the basis of the evidence about translocator protein (TSPO) overexpression on the outer mitochondrial membrane of tumor cells. The structure of the first TSPO ligand bearing a carborane cage (compound 2d) has been modified in order to find a suitable candidate for in vivo studies. The designed compounds were synthesized and evaluated for their potential interaction with TSPO and tumor cells. In vitro biological evaluation showed in the case of fluoromethyl derivative 4b a nanomolar TSPO affinity very similar to that of 2d, a significantly lower cytotoxicity, and a slightly superior performance as boron carrier toward breast cancer cells. Moreover, compound 4b could be used as a ¹9F magnetic resonance imaging (MRI) agent as well as labeled with ¹¹C or ¹8F to obtain positron emission tomography (PET) radiotracers in order to apply the "see and treat" strategy in BNCT.
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Boro , Encéfalo/efeitos dos fármacos , Proteínas de Transporte/metabolismo , Mitocôndrias/efeitos dos fármacos , Quinolinas , Receptores de GABA-A/metabolismo , Adenocarcinoma/diagnóstico por imagem , Adenocarcinoma/patologia , Adenocarcinoma/radioterapia , Animais , Sítios de Ligação , Boranos/síntese química , Boranos/farmacologia , Boranos/uso terapêutico , Boro/química , Boro/metabolismo , Encéfalo/metabolismo , Encéfalo/patologia , Neoplasias da Mama/diagnóstico por imagem , Neoplasias da Mama/patologia , Neoplasias da Mama/radioterapia , Proteínas de Transporte/química , Proteínas de Transporte/genética , Linhagem Celular Tumoral , Neoplasias do Colo/diagnóstico por imagem , Neoplasias do Colo/patologia , Neoplasias do Colo/radioterapia , Cristalografia por Raios X , Feminino , Radioisótopos de Flúor , Expressão Gênica , Imageamento por Ressonância Magnética , Masculino , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Modelos Moleculares , Tomografia por Emissão de Pósitrons , Ligação Proteica , Quinolinas/síntese química , Quinolinas/farmacologia , Quinolinas/uso terapêutico , Ratos , Receptores de GABA-A/química , Receptores de GABA-A/genética , Relação Estrutura-AtividadeRESUMO
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 (1)H, (13)C, (11)B, 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 (Φ(F)) of 0.14 and 0.08, and singlet oxygen quantum yields (Φ(Δ)) 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.