以耗散粒子動力學法研究囊胞在不同溫度下之物理性質與融合機制

Studies of Physical Properties and Fusion Mechanism of Vesicles at Different Temperatures by Dissipative Particle Dynamic Simulations

吳幸倫(Hsing-Lun Wu)

指導教授 ： 諶玉真

國立臺灣大學/工學院/高分子科學與工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.01438

摘要

囊胞是由脂質所組成的雙層膜球型聚集體，其構造類似生物體的細胞膜，此外囊胞擁有良好的生物相容性及生物降解性，因此廣泛應用於藥物釋放載體以及模擬細胞膜的各種反應。囊胞會受到溫度的影響，出現三種不同的型態，由低溫到高溫分別為tilted gel phase、rippled phase、liquid disordered phase。本研究利用耗散粒子動力學法來研究囊胞在不同溫度下，囊胞之物理性質的變化以及囊胞融合程序受到的影響。
根據模擬的結果，可以發現囊胞的大小、含水量，滲透率都隨著溫度升高而變大；而膜的厚度以及order parameter則隨著溫度升高而變小。囊胞的表面張力在第二相轉移溫度之前，隨著溫度上升而變大；在第二轉移溫度之後囊胞的型態轉變為liquid disordered phase，囊胞的表面張力隨著溫度上升而下降。此外測量不同溫度下囊胞的伸展模數，在第二相轉移溫度之前，隨著溫度上升而下降，表示越高溫越好拉；在第二相轉移溫度之後，隨著溫度上升而上升，表示越高溫越難拉。當脂質分子的尾端越疏水，rippled phase的範圍也變的越大，也能夠在更低的溫度形成囊胞。
將不同溫度和不同aBW的囊胞進行融合的模擬，可以發現融合的時間並不僅是像文獻上所說，隨著表面張力變大，融合的時間會變的更短。囊胞的滲透率可能也演了影響融合的角色，當滲透率越大，融合的時間會變的更長。若是表面張力與滲透率的影響互相競爭，變化比較大的一方將主導融合的趨勢。

關鍵字

囊胞 ； 相轉移 ； 脂質分子 ； 融合 ； 耗散粒子動力學法

並列摘要

Vesicles are spherical aggregates composed of lipid monomers. Its structure is similar to the cell membrane which exists in organisms. Vesicles are widely used for drug delivery carriers and simulation of cell membrane behavior due to their high biodegradability and biocompatibility. Vesicles are affected by temperature, and it changes its morphology form tilted gel phase to rippled phase and finally to liquid disordered phase when temperature increases. In this work, simulations based on dissipative particle dynamics are performed to study the temperature influence on vesicle. The effects of temperature on the physical properties and fusion process of vesicles are investigated.
According to the simulation results, we can find that the size, inner water, and permeability of vesicles are increasing when temperature increases. But the thickness of membrane and order parameter of vesicles is decreasing when the temperature increases. Surface tension increases with temperature before main transition, but decreases after main transition because the morphology of vesicles turns into liquid disordered phase. The stretching module decreases before main transition. It means that vesicles are easier to be stretched before main transition. After main transition, the tendency is totally different. When the lipid tails are more hydrophobic, the range of rippled phase is broader, and it is easier to form vesicles in lower temperature.
We use vesicles with different temperature or aBW to fusion process, and find that fusion time not only affect by the surface tension of vesicles, but also affect by the permeability. When surface tension increases, vesicles need less time to finish fusion process. Otherwise when permeability increases, vesicles are difficult to fuse. If the surface tension and the permeability competes with each other, which one changes more will dominate the trend of fusion.

並列關鍵字

vesicle ； phase transition ； lipid ； fusion ； DPD

參考文獻

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