- 學位論文
微脂粒在親疏水表面的吸附行為
Vesicles Adsorption Behavior on Hydrophilic and Hydrophobic Surface
摘要
囊胞或稱為微脂粒是由脂質所組成的雙層膜球形聚集體，其構造類似於生物體的細胞膜，並具有良好的生物相容性以及生物降解性，因此廣泛應用於生物性材料上。在醫學上，微粒子或微感應器必須進入生物體內蒐集資訊，能在生物體內停留很長的時間以及穩定的接收訊息，是很重要的，但由於微粒子及微感應器均由非生物性材料所製成，因此必須在外部塗抹一層生物性材質才能將其放入生物體內而不會產生排斥現象。囊胞的生物相容性以及可在外層接枝不同的官能基的特點，使其成為應用於生物感應器及表面改質的熱門課題。 本研究中，我們利用耗散粒子動力學法模擬囊胞和親�疏水板間的作用。我們的研究發現，當囊胞體積較小以及脂質疏水端較不排斥水時，囊胞的脂質排列整齊度較小，張力較大；當囊胞體積較大以及脂質疏水端較排斥水時，脂質排列整齊度較大，張力較小。囊胞和親水板作用，當囊胞張力低時，會成為完全不瓦解之囊胞；當張力逐漸上升，會成為部分瓦解之囊胞；當張力較大時，則會成為完全瓦解之囊胞，或稱為脂質雙層結構。囊胞和疏水板的作用，則由囊胞破裂後的癒合和後退攤平機制為主，當癒合速度快於囊胞攤平速度，則會形成部分瓦解之囊胞；當癒合速度慢於囊胞攤平速度，則形成完全瓦解之囊胞。 將囊胞內部塞入更多的水粒子使囊胞的張力值上升，會使得囊胞和親水板作用逐漸趨向完全瓦解之囊胞，與疏水板的作用則沒有影響。將囊胞內部抽出水粒子如同兩顆囊胞經過融合程序後之內部水粒子減少的樣貌，則囊胞和親水板的作用會因囊胞張力下降而傾向完全不瓦解之囊胞，和疏水板的作用則因內部水粒子減少而傾向完全瓦解之囊胞。將親�疏水基板和脂質親�疏水端粒子的斥力參數調小，使其更親近，則可使原本完全不瓦解之囊胞變為完全瓦解之囊胞，表示利用如改變溶液的電性或是改變親�疏水板材質，可以較輕鬆的將囊胞完全攤平於平板上，達到表面改質的目的。 最後我們研究基板上同時含有親水材質及疏水材質，發現囊胞會優先選擇和疏水材質作用，避免疏水材質和水碰觸，而已經在基板上形成脂質單層或雙層結構的粒子，則會促使原本不破裂的囊胞破裂，進而完全攤平於基板上。
並列摘要
Vesicles are spherical aggregates composed of lipid monomers. Its structure is similar to the cell membrane in organisms. Vesicles are widely used in biomaterials due to their high biodegradability and biocompatibility. In medical applications, it is important for nanoparticles and micro sensors to stay in organism for a long time to stably receive message. But nanoparticles and micro sensors are made of non-biological materials, thus it is necessary to coat a layer of biological material on the non-biological materials to prevent the rejection phenomenon in organism. The high biocompatibility and the ability for functional groups or proteins to be grafted upon have made vesicle become the most popular way for the applications of biosensors and surface modification. In this work, we use dissipative particle dynamics (DPD) to simulate the interactions between vesicles and hydrophilic/hydrophobic substrate. We find that when the volume of vesicle is small and the lipid tail is more hydrophobic, the order parameter of vesicle is small and membrane tension is large; when the volume of vesicle is large and the lipid tail is less hydrophobic, the order parameter of vesicle is large and membrane tension is small. When the membrane tension of the vesicle is low, the final morphology of vesicle interacting with hydrophilic substrates is non disintegrated formation; the morphology becomes partially disintegrated vesicle as tension increases; when tension is large, the vesicle develop into completely disintegrated state and a lipid bilayer is formed on the hydrophilic substrate. When vesicles interact with hydrophobic substrates, the key factors controlling the final morphology are healing and receding processes of lipids. After vesicle ruptures, vesicle tends to heal itself to the original form while lipid bilayer recedes from the rupture point. If the speed of healing is higher than that of receding, then the final morphology is partially disintegrated, or else the vesicle is completely disintegrated, and a lipid monolayer is formed on the hydrophobic substrate. Increasing the tension of vesicle by putting more water into the interior water region of the vesicle makes vesicle which interacting with hydrophilic substrate change from non disintegrated to completely disintegrated state. However there is no effect on the vesicle interacting with hydrophobic substrate. Shrinking the interior water region from vesicle to reduce the tension, which is the same as two vesicles fusion together, makes vesicle which interacting with hydrophilic substrate change form completely disintegrated to partially disintegrated status. For vesicle interacting with hydrophobic substrate, the shrinking of interior water region of vesicle leads to completely disintegrated formation. If we lower the interaction parameter of hydrophilic (hydrophobic) substrate and lipid hydrophilic (hydrophobic) beads, then the final morphology of vesicle tend to be completely disintegrated form. The result indicated that it is feasible to obtain lipid bilayer or lipid monolayer by changing substrates. Both hydrophilic and hydrophobic sections coexisting in one substrate is studied. The vesicles preferentially interact with hydrophobic section to prevent the hydrophobic part exposed to water. Also, the lipid bilayer or lipid monolayer formed first would cause vesicle to rupture and then become completely disintegrated.