由於自組裝單分子層的表面修飾技術製備簡易且可廣泛選用吸附物，因此在改質金屬表面性質時被視為一重要的技術。本研究利用一末端帶有仿生性亦具有雙電性質之磷脂質(PC)硫醇分子[ HS-(CH2)11-P(=O)(-O-)-O-CH2CH2N+-(CH3)3]製作自組裝單分子層，同時也利用不同的表面分析技術研究其性質。實驗變因包含三種溶劑(乙醇、甲醇以及水)與三種濃度(2mM、1mM、0.1mM)下製備不同成長條件之含磷脂質自組裝單分子層。表面分析方式包括靜態接觸角量測(CA)、化學分析電子能譜分布(XPS)、一次反射式傅立葉轉換光譜圖(RAIRS)、循環伏安法(CV)、交流阻抗頻譜分析(EIS)、界達電位量測(Zeta potential)。此外藉由在PBS緩衝液中保存35天以了解表面的穩定性，而利用血小板吸附實驗更可決定各種表面的血小板吸附行為。
表面分析結果顯示整體自組裝單分子層的排列品質以及末端磷脂質方向性受到成長環境中溶劑與濃度的差異影響。甚至溶劑與濃度效應也會影響到長時間穩定性以及血小板吸附行為。
在此我們提出假設，成長濃度、溶劑分子大小以及溶劑分子本身結構對稱性進而和磷脂質間形成偶極力的程度皆影響整體自組裝單分子層的結構以及末端磷脂質之方向性；以乙醇與甲醇為溶劑的條件下製備的自組裝單分子層時，末端磷脂質官能基較容易向外層延伸而使得在XPS實驗中觀察到較高的氮磷比；此外如乙醇與甲醇這些較大的溶劑分子以及結構使得溶劑本身能形成偶極力的能力較差，造成表面有較為無序的排列現象同時也會使得接觸角值高於水製備的樣品；相反的水分子本身較小且形成偶極力的能力也較強，因此促使硫醇分子間的-(PO3)-與-N(CH3)3+藉由靜電作用力而緊密連結在一起，而這種現象會造成末端PC官能基傾向向分子層之內層延伸同時也觀察到較低的氮磷比，由於排列現象的差異而造成水製備的樣品具有較為有序的排列以及較低的接觸角值。
濃度效應在乙醇與甲醇為溶劑的條件下製備的自組裝單分子層時，隨著成長濃度降低經由電化學分析以及接觸角量測時觀察到表面呈現較為親水以及較多缺陷的產生，這可能是因為濃度降低時造成分子間作用力較不複雜所產生的結果。此外，以水製備的表面當成長濃度下降時卻會使得排列更加無序，推測是因為分子間的靜電作用力降低以致無法在成長自組裝酖分子層時穩定排列結構，而接觸角值也說明濃度降低會有較為疏水之表面也與此現象息息相關。

Self-assembled monolayers (SAMs) technique has been recognized as an important surface modification method for tailoring the surface properties of metallic substrate due to its ease of preparation and wide choice of organic adsorbents. In this study, the structure of self-assembled monolayer formed by the alkanethiol with a cell-membrane mimicking zwitterionic terminal functionality, phosphorylchoilne [PC, HS-(CH2)11-P(=O)(-O-)-O-CH2CH2N+-(CH3)3], was investigated by various surface characterization techniques. Three different solvents (namely; methanol, ethanol and water) and three different alkanethiol concentrations (2 mM, 1mM and 0.1mM) were used to prepare various PC-terminated SAMs. The surface analysis techniques utilized include static contact angle measurement (CA), X-ray photoelectron spectroscopy (XPS), reflection adsorption infrared spectroscopy (RAIRS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and electo-kinetic analyzer (EKA). In addition, the stability of these PC-terminated SAMs was analyzed after being preserved within phosphate buffer saline (PBS) for 35 days. The in vitro platelet adhesion assay was also performed to determine the platelet compatibility of these PC-terminated SAMs.
Surface characterization results have indicated that the packing qualities and the orientation of PC terminal ends were affected by the solvent and the alkanethiol concentration used. Moreover, these two also affected the platelet compatibility and long-term stability of the PC-terminated SAMs.
A hypothetical model was proposed, in which the solvent size and dipole interactive capability and symmetry would affect the packing quality as well as the orientation of the PC-terminal ends of the SAMs prepared using different solvents and concentrations. For those prepared using methanol and ethanol, the PC-terminal ends would likely to extend outwards, leading to higher N/P ratio noted in XPS analysis. In addition, the larger molecule size and less dipole interactive capability of these two solvent molecules would lead to less ordered SAMs’ structures, resulting more tilting and more exposure of the hydrocarbon backbone as indicated by the higher contact angle values than those prepared using water as the solvent. In contrast, the water molecules that are smaller and having more symmetric dipole interactive capability would more favor the inter-chain electrostatic interactions between the –(PO3)- and –N(CH3)3+ that were associated with neighboring thiol molecules. This would result in a more inwards extension of PC-terminal ends, as indicated by lower N/P ratios, and a more ordered and less-tilting hydrocarbon backbone structure as shown by a lower contact angle value.
For those SAMs prepared with methanol and ethanol, the structure becomes less tilting as the thiol concentration was decreased, indicated by the decreasing contact angle value. This is likely due to the less complicated inter-chain interactions as the amount of solution thiol was deceased. On the other hand, for the SAMs prepared using water as the solvent, the structure become less-ordered as the thiol concentration was decreased, shown by the increase in hydrophobicity and more gauche conformation. This finding could be attributed to the decrease in electrostatic interactions that would stabilize the packing structure of these water-solvent-prepared PC-terminated SAMs.

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