許多疾病是由基因缺陷所引起，目前治療這類疾病最有潛力的方法之一，是利用非病毒載體壓實、包覆可修復基因缺陷之DNA，再將其投遞至細胞內以修復基因缺陷；雙子型界面活性劑便為其中一類極具發展性的非病毒載體。一般而言，載體與DNA所形成的複合物是由胞吞作用（endocytosis）進入細胞，在胞吞作用中所形成的核內體（endosome）會將複合物包覆在內，核內體的內部環境隨著發展過程逐漸轉變為酸性，以分解被胞吞之物質。因此，成功的載體必須在酸性環境下不被瓦解並同時保護DNA不被酵素分解，並由核內體逃脫（endosomal escape）以釋放出DNA達到轉染（transfection）的目標。過去的研究指出，在作為基因藥物載體時，酸鹼度敏感型雙子型界面活性劑較一般型雙子型界面活性劑擁有更佳的轉染效率。雖然科學家普遍推測此與前者擁有較佳的核內體逃脫能力有關，但卻無任何直接或間接之實驗證據證實此一推測，更不用說對其背後之分子機制的了解。因此，本研究利用UV光譜、原子力顯微鏡以及小角度X光散射，探討此兩類界面活性劑對改變DNA構型的能力，以及利用螢光光譜儀、小角度X光與中子散射，探討DNA由載體之釋放程度及複合物對仿核內體脂質囊泡在結構上的影響。藉由比較此兩類界面活性劑在各項性質上的差異，我們探究出酸鹼度敏感型雙子型界面活性劑擁有較高轉染效率的分子機制。;Genetic diseases arise from abnormalities in genome. A promising approach in treating these diseases is employ a non-viral vehicle to compact and encapsulate therapeutic DNAs and deliver them into cells to repair the genetic disorders; gemini surfactants are among the most anticipated candidates for the gene delivery vehicle. Generally, the complexes formed by DNAs and vehicles enter cells by endocytosis. The endosomes formed during endocytosis encapsulate the complexes and become increasingly acidic to break down the internalized substances. As a result, a successful vehicle needs to maintain its structural integrity in an acidic environment to protect the DNAs from degradation and simultaneously escape from the endosome to release the DNAs for the transfection to occur. Earlier studies found that pH-sensitive gemini surfactants, when deployed as gene delivery vehicles, achieved higher transfection efficacies than their pH-insensitive counterparts. It is speculated that the higher transfection efficacy results from the former’s better capability to escape from endosomes. However, experimental evidence, whatever direct or indirect, remains lacking, let alone the understanding of the underlying molecular mechanisms. To address the issues, this study employs UV spectroscopy, atomic force microscope, and small-angle x-ray scattering to examine how the two types of gemini surfactants modify the conformations of DNAs; and employs fluorescence spectroscopy and small-angle x-ray and neutron scattering techniques to examine the extents of the DNA release from the vehicles and structural perturbations on the endosome-mimicking liposomes. Through comparing the differences in these aspects between the two types of geminni surfactants, we uncover the molecular mechanism accounting for the high transfection efficacy of the pH-sensitive gemini surfactants.
