Radiolysis, Photolysis & Sonolysis--Cells & Constituents

工作总结：声动力疗法是一种很有前途的治疗癌症的新方法，它是基于声敏仪和超声波联合杀灭细胞的协同效应。超声波可以深入组织，聚焦在肿瘤的一个小区域，激活无毒分子(如卟啉)，从而将不良副作用降至最低。实验证据表明，声敏化是由于声增敏剂在热塌陷空化泡内部或附近的化学活化，通过敏化剂在水-气界面的直接热解，或由于水的热解形成的氢原子和羟基自由基的反应，形成敏化剂衍生的自由基。来自声波增敏剂的自由基(主要是以碳为中心的)与氧反应生成过氧基和烷氧基。与在空化气泡内热解形成的OH自由基和H原子不同，烷氧基和过氧基与生物介质中的有机化合物的反应活性要低得多，因此它们有更高的几率到达临界细胞位置。最近，我们成功地捕获了各种卟啉水溶液在超声分解过程中形成的碳自由基团。 溶质的表面活性剂性质在水溶液的声化学中起着重要的作用。最近，研究表明，对于相对低分子质量的表面活性剂，这些效应可以与溶质的吉布斯表面过剩相关联。我们使用具有良好特性的表面活性剂模型分子，通过考虑Gibbs表面过剩和动态表面张力的可能作用，研究了这种关联是否适用于相对高分子质量的表面活性剂，如声敏仪。结果表明，高分子表面活性剂的Gibbs表面过剩与水溶液中超声分解后的分解程度无关。相反，表面活性剂的分解取决于它们的化学结构以及它们在整体溶液和空化气泡的气体/溶液界面之间平衡的能力。

Summary of work: Sonodynamic therapy is a promising new modality for cancer treatment based on the synergistic effects of cell killing by a combination of sonosensitzer and ultrasound. Ultrasound can penetrate deeply into tissue and can be focused in a small region of tumor to activate non-toxic molecules (e.g. porphyrins ) thus minimizing undesirable side effects. The experimental evidence suggests that sonosensitization is due to the chemical activation of sonosensitizers inside or in close vicinity of hot collapsing cavitation bubbles to form sensitizer-derived radicals either by direct pyrolysis of the sensitizer at the water-gas interface or due to the reactions of hydrogen atoms and hydroxyl radicals formed by the pyrolysis of water. The free radicals derived from the sonosensitizer (mostly carbon-centered) react with oxygen to form peroxyl and alkoxyl radicals. Unlike OH radicals and H atoms which are formed by pyrolysis inside cavitation bubbles, the reactivity of alkoxyl and peroxyl radicals with organic compounds in biological media is much lower and hence they have a higher probability of reaching critical cellular sites. Recently we have succeeded in spin-trapping the carbon radicals formed during the sonolysis of aqueous solutions of various porphyrins . The surfactant properties of solutes play an important role in the sonochemistry of aqueous solutions. Recently, it has been shown, for relatively low molecular weight surfactants, that these effects can be correlated with the Gibbs surface excess of the solute. We investigated whether this correlation is valid for relatively high molecular weight surfactants, such as sonosensitzers, by considering the Gibbs surface excess and the possible role of the dynamic surface tension using model surfactant molecules, with well characterized surfactant properties. The results show that the Gibbs surface excess of high molecular weight surfactants does not correlate with the extent of decomposition following sonolysis in aqueous solutions. Instead, the decomposition of surfactants depends on their chemical structure and their ability to equilibrate between the bulk solution and the gas/solution interface of cavitation bubbles.