利用兩階段常壓電漿技術於聚乳酸表面改質處理之研究

Abstract

本研究主要致力於發展使用氮氣為主要反應氣體的介電質兩階段常壓電漿處理程序，來改進聚乳酸材料之表面性質。最佳化之兩階段電漿處理程序包含且依序地使用以下兩個步驟，1) 前處理電漿:氮氣加0.1%氧氣及2) 氨氣電漿: 氮氣加5%氨氣。結果顯示利用兩階段電漿處理，能讓我們有效且快速地植入大量的胺基於聚乳酸的表面，其氮/碳比 (N/C ratio)被提升至約0.19。另一方面，表面能，接觸角及表面粗糙度亦被分別提高至70.5 mJ/m2， 38˚ 及 73.22 nm。在細胞的實驗中，我們觀察到了細胞快速增生的結果，其表示這些改質後的表面性質皆十分有利於細胞的生長。更重要的是相較於傳統的gelatin改質方法，使用兩階段電漿處理能夠大幅地縮減處理且準備試片的時間由原本使用之13-15小時減至5-15分鐘。另一方面，使用不同電極長度對於電漿溫度，表面改質效果及細胞貼附與增生亦在此論文中被研究及討論。 結果顯示使用較短的電極能有效地降低電漿溫度，但也同時弱化了表面改質效果及細胞貼附與增生。最後，基於電漿光譜，X光電子能譜儀及原子力顯微鏡的分析，我們提出了一個簡化的表面化學反應機制來解釋對於使用兩階段電漿處理後胺基植入量大幅提升之現象。

A two-step plasma treatment procedure using the post-discharge jet region of atmospheric pressure (AP) nitrogen-based dielectric barrier discharge (DBD) was developed for better surface modification on Polylactide (PLA). The optimized plasma treatments were carried out in two steps in sequence, which include: 1) pretreatment plasma treatment to pretreat the surface using the N2 DBD jet with 0.1% addition of O2 in company with a moving speed of 1 cm/s for 40 passes, and 2) an ammonia plasma treatment to incorporate nitrogen-containing groups using the same N2 DBD jet, but with the addition of 5% NH3 and a moving speed of 2 cm/s for 80 passes. After applying the two-step plasma treatment, the X-ray photoelectron spectra (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analyses shows a remarkably enhanced nitrogen containing group, such as primary amine and primary amide, incorporation (N/C ratio of ~0.19) compared to that of either treatment alone. Moreover, the surface energy, contact angle and surface roughness are improved to 70.5 mJ/m2, 38˚ and 73.22 nm, respectively. These modified surface properties are confirmed to be very beneficial in improving cell growth on the PLA surface for mouse muscle myoblast cells (C2C12). On the other hand, the performance of surface modification and cell growth on two-step plasma treated PLAs implemented by electrodes with various lengths is investigated. the result shows that employing shortened electrodes allows not only an omission of water cooling system but also dramatic reduction of the plasma temperature down to 17℃ maximally compared to that using 5 cm electrode (52℃). Furthermore, 1 cm electrode would be chosen as the optimal approach for processing delicate medical devices owing to its low treatment temperature of 30℃ and greatly improved cell proliferation, which performs approximately 7% lowered optical density (OD) compared to that obtained by 5 cm electrode after 48 hours of culture. Lastly, a surface amination mechanism is proposed based on the observations of optical emission spectra (OES), atomic force microscope (AFM) and XPS analyses for explaining experimental observations.