Quantitative Subcellular Secondary Ion Mass Spectrometry (SIMS) Imaging of Boron-10 and Boron-11 Isotopes in the Same Cell Delivered by Two Combined BNCT Drugs:In VitroStudies on Human Glioblastoma T98G Cells

Abstract

Ion microscopy was used for subcellular quantitative imaging of the isotopes 10B and 11B in the same cell to evaluate boron delivery using a mixture of two neutron capture therapy drugs, p-boronophenylalanine-fructose (BPA-F) and sodium borocaptate (BSH). The application of 10B-labeled BPA-F and 11B-labeled BSH allowed independent imaging of both 10B and 11B in the same cell using a CAMECA IMS-3f ion microscope. Mixed-drug treatments were compared to single-drug exposures given under identical conditions. 10BPA-F delivered 10B heterogeneously to T98G human glioblastoma cells, with a significantly reduced concentration in an organelle-rich perinuclear region. The intracellular distribution of 11B from 11BSH contrasted with that of the 10B from 10BPA-F, with 11B distributed nearly homogeneously throughout cells. The subcellular distributions of 10B and 11B were sustained in mixed-drug treatments and resembled their localizations after the single-drug treatments. In both single- and mixed-drug treatments, cellular levels of 10B from 10BPA-F nearly doubled between 1 h and 6 h, with a 3:1 intracellular to nutrient medium partitioning, while cellular levels of 11BSH remained essentially unchanged. The net effect of the combined treatment with 10BPA-F and 11BSH was an additive delivery of boron to cells. This study introduces a novel approach for checking potential synergistic, antagonistic or simple additive delivery of two mixed boronated compounds in cellular/subcellular compartments.

Laser postionization secondary neutral mass spectrometry in tissue: a powerful tool for elemental and molecular imaging in the development of targeted drugs

“…It could be shown that both compounds are capable of delivering 10 B to the desired target, the cell nucleus, but also to further intracellular compartments. Our study confirmed most assumptions from cell culture experiments by Chandra et al (32). As opposed to their work, however, within the tumor tissue, we observed a markedly heterogeneous distribution of BPA delivered 10 B on both intracellular and intercellular levels.…”

“…SIMS, an alternative technique for element-and molecule-specific imaging, has also been used for imaging boron compounds in cell cultures (31,32) and tissues (33,34). However, its application for imaging drugs is substantially hampered due to its lack of sensitivity and accuracy.…”

Boron analysis and boron imaging in biological materials for Boron Neutron Capture Therapy (BNCT)

“…Although SIMS has many advantages and has often been used in the dynamic SIMS mode for imaging boronated compounds in cell cultures and tissues [74][75][76][77][78][79], its application for boron imaging is often limited because of a lack of sensitivity and quantification. Detection limit, efficiency, and quantification, however, can be significantly improved by the use of laser-SNMS [80][81][82][83].…”

Compounds for neutron capture therapy and their distribution in tumors and surrounding tissues of animals (A review)

“…In contrast, BPA is transferred via the L-amino-acid transport system [19] and exhibits heterogeneous distribution inside the cell, being accumulated primarily in the nucleus and cytoplasm and having significantly lower concentration in a near-nuclear region (mitochondria, Golgi apparatus) [6,19,20]. It was also demonstrated [19] that, as the time of incubation of T98G human glioma cells in a BPA solution was increased from 1 to 6 h, the intracell boron content exhibited a threefold growth, whereas BSH did not show such accumulation. This implies that an increase in the intracell boron content requires infusion of BPA.…”