基因治療是指將一段正常基因送進病人細胞中，使細胞能夠合成正常生理所需的蛋白質，進而治療疾病。基因透過傳遞系統有效率地傳送至細胞，需要一安全且轉染率高的基因載體。在陽離子型高分子的基因傳輸系統中，高分子與DNA 自組裝地形成一奈米尺度的複合體，並藉由細胞胞飲作用進入細胞質，且能夠保護DNA 免於受到核酵素分解。然而，陽離子型高分子/DNA 複合體經由胞飲作用進入細胞之後，主要仍存留在內質體及溶小體中，限制了它們繼續在細胞質中運輸，因此，DNA 自內質體釋出將是基因傳輸系統中達成轉染效果的限制步驟。除此之外，PLL、PDMAEMA、及PEI 都是非生物可分解的材料，且具有明顯的細胞毒性，為了改善上述高分子的缺點，本研究室將以下五項特性作為合成或? 合新的陽離子型高分子基因傳輸系統結構設計的準則：(1)聚集DNA 的能力(2) 水溶蝕性(3)生物相容性(低細胞毒性)(4)pKa 值介於5.0~7.4(5)容易合成及?合。以目前而言，質體DNA 被廣泛地用於治療藥物及疫苗接種，然而，深入的研究發現，DNA 接種疫苗的成功關鍵在於傳輸系統。高分子材料亦被常用於疫苗接種的傳輸系統，而此類的高分子乃以物理包陷的方式包覆DNA 疫苗且成功地傳遞至細胞。本研究主要目的在設計具低細胞毒性、高基因傳輸能力之高分子傳遞系統，研究擬分三年完成，計畫主要工作如下：第一年新陽離子型聚酯高分子之合成及其質子海綿效應與DNA/高分子奈米複合體基因轉染效率關係之研究第二年利用?合方法改質基因傳輸用高分子材料及轉染效率評估第三年Poly(PEG-Ether-Anhydride)/Poly(Amino ester)s 奈米微粒作為質體DNA 疫苗傳輸載體之研究 Gene therapy is defined as delivery of therapeutic genes for expression into patient』s host cells to enable production of proteins to correct or moderate disease. To achieve gene delivery, safe vectors with selective and high transfection efficiency are required. The polycation/DNA complexes not only can protect the DNA from nuclease degradation,but also has a nanoscale size small enough to enter the cell via endocytosis. However, the delivery vehicle is localized in the endosome and will ultimately be trafficked to the lysosome. Release of the delivery vehicle from these compartments into cytoplasm is believed to be the limiting step in transfection mediated by many cationic polymers. In addition, these polycations such PLL、PDMAEMA、and PEI are nonbiodegradable materials and associated with a considerable degree of cytotoxicity. In point of improving their drawbacks, we outlined five criteria to drive the rational synthesis and blend to formulate new cationic polymer gene delivery systems.(1) DNA condensation capability(size of complex below 150 nm to allow efficient endocytosis)(2) hydrolytic degradation(3)biocompatibility(to minimize potential toxic effect)(4) pKa between lysosome pH(~5.0) and cytoplasmic pH(~7.4)(to provide buffer capacity)(5) facile synthesis and blend At present, it is broadly accepted that plasmid DNA has potential not only as a therapeutic agent but also as a new vaccination approach. However, as reseach in this field advances, it becomes evident that the use of plasmid DNA-based vaccines will largely depend on the development of efficient delivery systems. Polymeric materials have found wide use in DNA-based vaccines applications. These polymers generally serve as gene carriers through physical entrapment for the eventual intracellular delivery of their gene payload. The goal of this project is to design new biodegradable cationic polymers with low cytotoxicity and high transfection efficiency that can be used as vectors for gene delivery. Works of this project were carried out by the following three years. First year Synthesis of new cationic polyesters and study on relation between proton sponge effect and transfection efficiency of polymer/DNA nano-complexes Secondary year Characterizations of new cationic polymers obtained through polyblend method and study on their gene delivery efficiency. Third year Study on characterizations of poly(PEG-Ether-Anhydride)/poly(amino ester)s microsphere(nanosphere) as a DNA vaccine carrier and their delivery efficiency.
