Boron carrier

Scheme 2.2-22. Porphyrins [69] and chlorins with B12H11SH2 as boron carrier.

Porphyrins are chromophores, occurring in diverse molecules, such as hemoglobin and chlorophyll. They have a propensity to accumulate in tumors (81). Boronated porphyrins or their derivatives have great potential as boron carriers in boron neutron capture therapy (82). 

Molecular design and synthesis of boron carriers for neutron-capture tumor therapy 91PAC423. 

Hydroxyl forms of boronophenylalanine were synthesized by conjugation with a cascade of polyols to decrease the uptake of normal parenchyma without affecting uptake into the tumor (Takagaki et al. 1996). These forms might be more suitable boron carriers since the neutron irradiation injury to the normal parenchyma surrounding the tumor is reduced. 

Total syntheses of six carboranyl-containing porphyrins bearing 33-44 wt% B for application in BNCT was described by Vicente et al. (2000). This class of compounds features carbon-carbon linkages between the carboranyl groups and the meso-phenyl substituents. The synthesis of tetra (4-carboranylphenyl) porphyrins and their zinc(ll) complexes also was presented (Vicente et al. 2002b). This type of nido-carboranylporphyrin is a promising sensitizer for both BNCT and the photodynamic therapy of tumors. Four more nido-carboranylporphyrins showed promise as boron carriers for the BNCT (Vicente et al. 2002a). 

Takagaki, M., K. Ono, Y. Oda, H. Kikuchi, H. Nemoto, S. Iwamoto, J. Cai, and Y. Yamamoto. 1996. Hydroxyl forms of p-boronophenylalanine as potential boron carriers on boron neutron capture therapy for malignant brain tumors. Cancer Res. 56 2017-2020. 

LiB has been so far unknown. We think they probably have a polar-covalent type of the chemical bonds, which is similar to the ionic type. In the LiCl melt, which contains a certain amount of free delocalized electrons, the said borides may dissociate to lithium cations and boron anions having the hypothetical composition B . The latter may serve as the boron carriers from pure boron or the higher lithium borides to the metal particles. As a result, thermodynamically stronger borides of refractory metals are formed through diflhision. 

Spatial distribution mapping of the two boron carriers used in clinical trials, borocaptate(BSH) and 4-boronophenylalanine(BPA), has been obtained in vivo rat brain. The BSH map in excised rat brain and the F-BPA image using F-MRI in vivo rat brain were reported. Double resonance B-editing H-detection sequence, named M-Bend, was developed for the BSH image, exploiting the J-coupling interaction between B and nuclei. 

Cholesterol is an important constituent of the mammalian cell membrane and is a frequently used component of liposomal formulations in drug-delivery technology. Numerous cholesterol derivatives containing boron cluster attached to the cholesterol skeleton as external entities have been synthesized as potential boron carriers for BNCT. In general, two types of cholesterol boron cluster... 

Oligonucleotides received interest as boron carriers, because it is supposed that they can selectively target tumor cells that contain overexpressed genes. Another important advantage would be that... 

Lesnikowski, Z. J. Paradowska, E. Olejniczak, A. B. Studzinska, M. Seekamp, P. SchuPler, U. Gabel, D. Schinazi, R. E Plesek, J., Towards new boron carriers for boron neutron capture therapy metaUac-arboranes and their nucleoside conjugates. Bioorg. Med. Chem. 2006,13,4168-4175. 

Ciofani, G. Raffa, V. Meniassi, A. Cuschieri, A., Folate Functionalized Boron Nitride Nanotubes and their Selective Uptake by Glioblastoma Multiforme Cells Imphcations for their Use as Boron Carriers in Clinical Boron Neutron Capture Therapy. Nanoscale Res. Lett. 2009, 4,113-121. 

In the last decade, boron carrier development has taken two directions small boron molecules and boron-conjugated biological vehicles. Unlike approaches using pharmaceuticals, boron carriers... 

El-Zaria, M. E. and Nakamura, H. 2009. New strategy for synthesis of mercaptoundecahydrododecaborate derivatives via click chemistry Possible boron carriers and visualization in cells for neutron capture therapy. Inorg. Chem. 48 11896-902. 

Gabel, D., Moller, D., Harfst, S. et al. 1993. Synthesis of i-aUcyl and -acyl derivatives of mercaptoundecahy-drododecaborate, a possible boron carrier for neutron capture therapy. Inorg. Chem. 32 2276-78. 

Recently, some other boron carriers were used to deliver polyhedral boranes into tumor cells. One of the most interesting and new direction is developments in the BNCT driven by nanotechnology [142-147]. This subject will not be discussed here since a special chapter is planned in this book. Carboranylquinazolines [148], carboranyl aminoalcohols [149], carboranyl-a-acyloxy-amides [150], carboranyl glycophosphonates [151], conjugates of icosahedral dicarboranes with cobalt bis(dicarbollide) [152], and platinum complexes containing carborane [153] have been obtained as potential candidates for BNCT. 

T. Sano. Boron-enriched streptavidin potentially useful as a component of boron carriers for neutron capture therapy of cancer. Bioconjugate Chem., 1999,10, 905-911. 

Masunaga, S.-L Ono, K. Kirihata, M. Takagaki, M. Sakurai, Y. Kinashi, Y Kobayashi, T. et al., Potential of alpha-amino alcohol p-boronophenyMaiunol as a boron carrier in boron neutron capture therapy, regarding its enantiomers. J. Cancer Res. Clin. Oncol. 2003,129, 21-28. 

Kabalka, G. W. Yao, M.-L. MarepaUy, S. R. Chandra, S. Biological evalnation of boronated unnatural amino acids as new boron carriers. App. Rad. Isotopes 2009, <57, S374—S379. 

Lesnikowski, Z. J. and Schinazi, R. F. 1995. Boron neutron capture therapy of cancers Nucleic bases, nucleosides, and oligonucleotides as potential boron carriers. Polish J. Chem. 69(6) 827-840. 

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