利用聚電解質多層膜修飾材料表面以調節宿主反應

Abstract

普遍上，人造的植入物，往往會面臨一個被緻密膠原所包覆的宿命，這也就是所謂的異物莢囊包覆反應。文獻上，許多學者嘗試由許多方向著手，去防止異物反應的產生。最近，有一種簡單且重要的表面修飾方法，此種方法係藉由兩種不同電荷的聚電解質之間的靜電吸引力來修飾材料表面，它於固定胜肽物質於材料表面上，展現巨大的潛力。這種一層接著一層，所形成之極薄多層膜，係藉由交互吸附兩種相反電荷電解質於其溶液中而達成。此研究的主要目標即是利用聚電解質多層膜修飾材料表面，以改善宿主對生醫材料所產生的負面反應。 在初部階段，我們使用膠原蛋白與玻尿酸此兩種公認具良好生物相容性的材料，並於pH 4的醋酸的緩衝液中，組裝該多層膜。我們分別在體外與動物體內進行生物相容性的檢視。我們使用RAW 264.7老鼠巨噬細胞細胞株，以進行體外實驗。實驗結果顯示細胞數與一氧化氧的產生量，相對於PDMS表面上，有降底的趨勢。細胞形態方面，多層膜上的細胞呈現較圓的形態，且彼此相互聚集，然而細胞於PDMS表面上，則是較為伸展、攤平；施加酯聚醣刺激後，多層膜上的細胞大部分依舊維持原本的型態而在PDMS上則更為伸展並延伸它們的觸角，呈現樹狀細胞的形態。經由染色發現，所有的表面皆無對細胞產生傷害。我們接著將多層膜修飾的表面植入老鼠體內，經過3週與6週後取出觀察，結果顯示，相較於PDMS，多層膜修飾過的表面產生較低程度的緻密包覆。而我們歸因這些現象與影響是膠原蛋白或者玻尿酸的特性所產生的貢獻。 接著我們固定使用十偶層數的多層膜，並探討不同pH及正電荷電解質種類的影響。結果顯示在pH 10環境下所組裝的PLL/HA 多層膜是細胞數最低的條件之一。然而之後的螢光染色卻顯示，大部分細胞在該表面上是死亡的，且細胞是呈現活化的狀態。我們繼續挑選其它的表面，沿用了初始部分的pH 4緩衝液來組裝多層膜，以避免過多的正電解質被吸附於材料表面。我們使用數種常見之合成與天然聚電質的多層膜組合，進行短時間的貼附測試。結果顯示由天然高分子組成的多層膜，有較少細胞貼附的趨勢，而同時我們改變吸附在最上層的種類與吸附時的鹽濃度，可以發現細胞貼附數量，因此被影響。幾個細胞貼附較少的表面被繼續投入測試，而結果顯示在這些表面上細胞的一氧化氮產生量亦有降低的趨勢，特別是於某些表面上，產生的量甚低於未加酯聚醣刺激的PDMS表面。我們將結果最好的三種表面，再次植入老鼠體內進行觀察，三週後組織被取出分析，而結果顯示經修飾過的表面能縮減緻密包覆的產生。 整體而言，我們成功降低宿主對於生醫材料產生的負面反應，而此種聚電解質多層膜修飾材料表面的方法，展現它對於改善植入物生物相容性的無限潛力。

It is well known that long-term artificial implants frequently failed to turn on normal healing process, but were encapsulated by a thick, fibrous collagen layer, known as foreign body reaction (FBR). Attempts to prevent FBR to artificial implants have been the focus of many studies. Recently, a simple and versatile method based on electrostatic attractions between oppositely-charged polyelectrolytes shows its potential for peptide immobilization. This technique of layer-by-layer (LBL) polyelectrolyte multilayer (PEM) deposition is based on the alternate adsorption of positively and negatively charged polyelectrolytes to build an ultra-thin film onto a substratum. The aim of this work is to apply this surface modification technique for improving host response to implants. In the first part, PDMS samples were alternatively adsorbed in variant solutions at pH 4 acetate buffer to build the multilayer films. The formed substrates were tested in vitro and in vivo models for evaluating biocompatibility. Macrophage-like cells, RAW 264.7 murine macrophage / monocyte cells were applied in our study. The cell numbers and NO production were decreased on the PDMS precoated with 20 bilayers of COL/HA compared to the unmodified PDMS. Cell morphology on the unmodified PDMS was spread, while that on the LBL modified PDMS was aggregated and rounded. No sign of cytotoxicity of the LBL films was found on. These results were discussed, and we contributed these effects to the biological function of COL or HA. The COL/HA modified PDMS was implanted subcutaneously in rats and explanted after 3 or 6 weeks. Preliminary results indicated that LBL-modified surface elicited a thinner collagen encapsulation compared to the unmodified samples. For the second part, we fixed the number of bilayers at 10, and investigate the factor of pH and species of polycations. Result indicated PLL/HA built at pH 10 were with a lowest cell number while it was proven due to the cytotoxicity which might result from PLL by both live and dead staining and activation test. We kept on searching other surfaces of multilayer films while they were assembled at pH 4 buffers instead of neutral or higher pH values in later experiments. Both synthesized and natural polymers were used. Results showed there were fewer RAW 264.7 cells on PEM composed of specific natural polycations and the performance could be varied by condition of construction such as salt concentration and adsorbed species of the top. Activation test revealed that surfaces with fewer cells brought about lower level of NO production. The NO production on some of them was even lower than the PDMS control without LPS. Surfaces with prefer expression were implanted, and preliminary results indicated these surface had a reduced capsule formation as previous. In conclusion, the technique of LBL deposition shows a potential to improve the biocompatibility of implants.