在金屬合金類生醫材料的領域中，由於鈦基材料具有相對良好的生物相容性，良好的機械強度及非磁性，以及良好的抗腐蝕性而被廣泛用以取代傳統的不鏽鋼及鈷合金材料。然而在臨床上發現鈦基材料有血液相容性及抗生物聚集(anti-biofouling)能力不佳、植體與原骨整合時間過長等問題而限制其在硬組織取代、骨接合裝置以及心臟瓣膜、血管支架等方面的應用性。
目前常見的鈦金屬表面改質技術有以微加工、研磨、噴砂、拋光及化學蝕刻、陽極處理等方式使其表面產生奈米級粗糙度，表面以物理或化學方式固定具良好血液相容性、抗生物聚集性或骨相容性的分子等等方式，然而現今的改質方式大多針對特定用途而施行，因此並不足以涵蓋其廣泛的應用。由先前學者研究中發現表面固定化技術常使用矽烷基(silane)以及亞磷酸/亞磷酸酯基(phosphonic acid/phosphonate)作為錨定基團(anchoring group)。因傳統使用的矽烷改質層在生物體內穩定性不佳，且不易形成均勻表面而逐漸為亞磷酸/亞磷酸酯所取代；此外因高分子共聚物有可藉由單體所帶不同官能基並經由簡易的聚合反應展現出不同的外顯功能，綜合以上兩點，在本研究中希望發展出一改質平台除能與鈦金屬表面有良好連結性外並具有功能上的可調性以及製作上的便利性，以期能因應鈦基材料的廣泛應用。
先前研究發現受限於亞磷酸/亞磷酸酯吸附於金屬氧化物之機制，如以傳統浸泡方式欲得到一緻密表面吸附層需要較長時間，因此在本研究中將採用Tethering By Aggregation and Growth (T-BAG)之新式塗佈方式以求能在更短時間內得到一均勻且緻密之表面吸附層。
學者研究指出硫代甜菜鹼官能基(-N+(CH3)2(CH2)3SO3-)具有無毒性、在大範圍pH內可保持其雙電性、良好的血液相容性以及抗生物聚集功能，故在本研究中將合成一共聚物同時具有可與鈦金屬錨合之亞磷酸基團以及此一硫代甜菜鹼官能基，並藉由NMR、FTIR、GPC 、TGA對共聚物進行鑑定；再將高分子以T-BAG方式塗佈於鈦金屬表面後以XPS (X-ray photoelectron spectroscopy)、CA (contact angle)、in vitro platelets adhesion以及SBF (simulated body fluid)-soaking探討其改質層穩定性、血液相容性以及潛在的骨誘導能力。
綜合所有實驗分析可知經由本研究提出之共聚系統可成功合成接近單分布(monodisperse)之共聚產物，並且在錨定單體與雙電性單體的進料比例為2：8時可得到具有最佳血液相容性之共聚物；然而在模擬體液浸泡時可能因所用錨定單體結構疏水性影響而抑制改質層對鈣成分之親和力，並使改質表面無法展現預期的骨誘導性。

Because of titanium-based materials having a relatively good biocompatibility, good mechanical and non-magnetic properties, and good corrosion resistance, it has been widely used to replace traditional stainless steel and cobalt alloy in the field of metallic and alloy type of biomaterials. However, owing to the problems associated with poor hemocompatibility and anti-biofouling ability and long bio-integration time after implantation, the application of titanium-based materials have been limited on hard tissue replacement, osteosynthesis devices, heart valves and vascular stents.
There are some commonly used titanium surface modification techniques, for example, micro-machining, grinding, sandblasting, polishing, chemical etching and anodizing for creating nanoscale roughness onto titanium surface; and surface immobilization of specific molecules through physical or chemical way for making surfaces with good hemocompatibility, anti-biofouling capability or osteocompatibility. Nevertheless, these surface modification schemes are mostly limited to specific applications and cannot be applied for the needs of other biomedical application. Hence, to create a versatile surface modification scheme is greatly needed.
From previous scholars' researches, surface immobilization technique commonly utilized a silane or phosphonic acid/phosphonate as the anchoring group. Due to poor stability of silane modified layer in vivo and difficulty in forming an uniform surface, silane was gradually replaced by the phosphonic acid/phosphonate as the anchoring group of choice. In addition, copolymerization between different functional monomers can lead to materials with a wide variety of functions conveniently. Henceforth, creating a monomer with unsaturated functionality and phosphonic acid/phosphonate terminal end for subsequent copolymerization is proposed in this investigation for surface modification of titanium-based metallic biomedical material.
Previous studies have noted that it will cost time to form a dense phosphonic acid/phosphonate containing layer onto titanium metal oxide surface using traditional dipping process. To overcome this drawback, a novel coating process, T-BAG (Tethering By Aggregation and Growth), is proposed with an aim to form a uniform and dense phosphonic acid/phosphonate layer in a shorter period.
Researchers have pointed out polymer with sulfobetaine functionalities is non-toxic, zwitterionic in a wide range of pH, hemocompatible as well as anti-biofouling. To incorporate these unique properties for biomedical application, a copolymer with sulfobetaine functionality and phosphonic acid group, by which a covalent bond can be formed between the titanium and copolymer through the T-BAG process, is synthesized in this investigation and will be characterized with NMR, FTIR, GPC and TGA. After that, the stability of this copolymer layer on titanium as well as its hemocompatibility and osteoinductivity will be characterized through XPS, static contact angle, in vitro platelets adhesion and simulated body fluid-soaking testing.
The copolymerization scheme employed can generate a copolymer with PDI close to 1. In addition, the copolymer with the highest hemocompatility is synthesized under feeding ratio of 2:8 (anchoring monomer to zwitterionic-terminated monomer). Nevertheless, the hydrophobic characteristic associated with the long alkyl chain within the anchoring monomer may inhibit the attachment of calcium ion onto the modified layer, resulting a low osteoinductivity.

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