On the Diffusion of Hypericin in Dimethylsulfoxide/Water Mixtures鈥擳he Effect of Aggregation

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• 作者：Gregor Ba虂no虂 ; Jana Stanic虒ova虂 ; Daniel Jancura ; Jozef Marek ; Mikula虂š ; Ba虂no虂 ; Jozef Ulic虒ny虂 ; Alena Strejc虒kova虂 ; Pavol Mis虒kovsky虂
• 刊名：Journal of Physical Chemistry B
• 出版年：2011
• 出版时间：March 17, 2011
• 年：2011
• 卷：115
• 期：10
• 页码：2417-2423
• 全文大小：890K
• 年卷期：v.115,no.10(March 17, 2011)
• ISSN：1520-5207

文摘

Hypericin (Hyp) is a natural photosensitizing pigment with a possible application in the photodynamic therapy of cancer. Hyp is readily dissolved in dimethylsulfoxide (DMSO) but forms nonsoluble aggregates in an aqueous environment. Fluorescence spectroscopy and diffusion coefficient measurements are used to investigate the self-association of Hyp molecules in DMSO/water mixtures. Fluorescence measurements reveal that Hyp remains in its monomeric form in DMSO/water mixtures containing up to 20鈭?0 wt % water. At higher water concentration, Hyp starts to form nonfluorescent aggregates. To determine the size of the aggregates, the diffusion coefficient of Hyp is determined for different DMSO/water mixtures both experimentally and theoretically. Our data indicate that the size of the aggregates increases as more water is added into DMSO. At 50 wt % water content, the effective diffusion coefficient is about 30% smaller than the calculated value for the stacked Hyp tetramer. The results indicate that in an aqueous environment, Hyp presumably produces large molecular weight stacked H-aggregates. We have also confirmed that in an aqueous environment at alkaline pH, molecules of Hyp remain in the monomeric state.