在傳遞DNA至人體細胞核以進行基因治療的過程中，DNA必須被壓實以降低遭受酵素分解或環境影響的機會，而因壓實而縮小之DNA亦較為容易進入至細胞核中。反之，DNA的被解壓實則是基因治療中的另一個必要步驟，以使DNA得以恢復原先之構型，並進行其基因表現之功能。傳統的單鏈型陽離子或陰離子界面活性劑對DNA的壓實與解壓實效果及其作為非病毒型基因載體的可能性經常是許多研究探討的主題。基於此一研究趨勢，本研究發展出一個以雙子型界面活性劑為基礎的新穎DNA壓實/解壓實系統。雙子型界面活性劑是由一條分子鏈將兩個單鏈型界面活性劑結合為一的一類界面活性劑；此一特殊的分子結構，使其比單鏈型界面活性劑具有更好的表面活性，並可藉由對橋接分子鏈的改變調整其分子結構及性質。在本研究中，我們使用了紫外光分光光譜儀、圓二色光譜儀、原子力顯微鏡及小角度X光散射等技術，探討不同的橋接分子鏈長度如何影響雙子型界面活性劑對於DNA壓實與解壓實之效果及其作用的機制。實驗數據顯示，陽離子與陰離子雙子型界面活性劑各自具有使DNA壓實與解壓實之能力，且橋接分子鏈之長度為6個碳數的雙子型界面活性劑對於DNA的壓實與解壓實效果皆較長度為3個碳數之雙子型界面活性劑為佳。我們推測，DNA壓實效果上的差異應與陽離子雙子型界面活性劑分子的離子化程度及其與DNA的複合自組裝結構的不同有關；而在DNA解壓實上的差異，我們則推測與陰離子雙子型界面活性劑的疏水性以及溶液中陰離子雙子型界面活性劑的帶電荷量有關。本研究因此以分子特性及超分子自組裝結構的角度，解釋了雙子型界面活性劑於DNA壓實/解壓實上的作用機制。;For an efficient delivey into the nuclei of human cells, the therapeutic DNAs of a gene therapy need to be compacted to protect them from the enzymatic hydrolysis or external chemical/biochemical stresses; the reduced DNA sizes by compaction also facilitate their delivery to the nuclei. On the other hand, decompaction of the compacted DNAs, which restores the DNAs to their native conformations and re-activates the gene expression, is a prerequisite for an effective gene therapy. Conventional cationic and anionic surfactants are often studied for their respective capabilities to compact and de-compact DNAs, with their potential of being a safe non-virus gene delivery system evaluated. Following this research interst, the present study develops a novel DNA compaction/decompaction system based on gemini surfactants. Gemini surfactants are dimers of two conventional surfactant molecules connected with a spacer. Due to this unique molecular structure, gemini surfactants commonly display superior surface activities than their conventional counterparts, with their molecular structure and material properties tunable via modulating the spacer. Here, we synthesize cationic and anionic gemini surfactants of varying spacer lengths to investigate how and why the change in the molecular structures of the gemini surfactants affects their DNA compaction/decompaction efficacy by using UV-vis spectrophotometer, dynamic light scattering, atomic force microscopy, circular dichroism and small-angle x-ray scattering. The gemini surfactants are proven competent in the DNA compact/decompaction, and the gemini surfactants with the 6-carbon long spacer are observed to display higher DNA compaction/decompaction efficiency than the one with the 3-carbon long spacer. The discrepancy in the DNA compaction efficacy might arise from the differences in the ionization degrees of the cationic gemini surfactants and in the self-assembled structures of the DNA-surfactant complexes. For the DNA decompaction, the difference in hydrophobicity and ionization of the anionic gemini surfactants may potentially lead to the difference in efficacy. The present study therefore explains the mechanisms underlying the DNA compaction/decompaction by gemini surfactants in terms of molecular property and supramolecular structure.
