Positive cooperativity in the cellular uptake of a boronated porphyrin

Intracellular uptake of a new boronated porphyrin EC032

We measured the toxicity and intracellular uptake of a newly developed boronated porphyrin EC032, and verified the fluorescence-based boron concentration measuring methods. Toxicity study showed that concentration required to produce a 50% reduction in viability (IC(50)) of EC032 was more than 0.25 mM. Fluorescence study showed the intracellular uptake of EC032 increased up until 24 h after its exposure to C6, 9L, U87, and U251 cells. There was also a linear correlation between ICP-AES and fluorescence intensity as an arbitrary unit about measurement of boron concentration. Fluorescence-based boron concentration measuring methods are very simple and useful methods, especially for screening of slight test dose of porphyrin compounds.

High level of low-density lipoprotein receptors enhance hypericin uptake by U-87 MG cells in the presence of LDL

The dependence of the uptake of hypericin (Hyp) by human glioma U-87 MG cells on the level of expression of low-density lipoprotein (LDL) receptors has been studied in this work. A special role of the LDL receptor-pathway for Hyp delivery to U-87 MG cells in the presence of LDL was revealed by the substantial increase of Hyp uptake in the situation, when the number of LDL receptors on the cell surface was elevated. Moreover, the colocalization experiments showed the lysosomal localization of Hyp following the uptake and that the concentration of Hyp in these organelles was enhanced in the cells with elevated number of LDL receptors when the incubation medium contained LDL. Both these findings suggest that LDL and LDL receptor-pathway play an important role in the delivery and accumulation of Hyp into the cells.

Synthesis and in vitro properties of trimethylamine- and phosphonate-substituted carboranylporphyrins for application in BNCT

A series of carboranylporphyrins containing either amine or phosphonic acid functionalities and two to six closo-carborane clusters have been synthesized via a [2+2] condensation of a dimethylamino- or diethylphosphonate-substituted dipyrromethane with a dicarboranylmethyl-benzaldehyde. The X-ray structures of four key reaction intermediates (1, 2, 3, and 4a) and of two target porphyrins, the diphosphonate ester- and the diamino-tetracarboranylporphyrins 5b and 6a, are presented and discussed. In vitro studies using human carcinoma HEp2 and human glioblastoma T98G cells show that these porphyrins are non-toxic in the dark up to 100 microM concentrations, and that a tetracarboranylporphyrin bearing two quaternary ammonium groups is the most efficiently taken up by cells at short times (up to 8 h), followed by a dicarboranylporphyrin bearing three phosphonic acid substituents. All carboranylporphyrins delivered therapeutic amounts of boron to T98G cells and localized mainly within the cell lysosomes.