Nakano Hiroki, Noguchi Yuri, Kakinoki Sachiro, Yamakawa Mai, Osaka Issey, Iwasaki Yasuhiko
Graduate School of Science and Engineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-0836, Japan.
Faculty of Chemistry, Materials and Bioengineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-0836, Japan.
ACS Appl Bio Mater. 2020 Feb 17;3(2):1071-1078. doi: 10.1021/acsabm.9b01040. Epub 2020 Jan 10.
For improving lubricity, the formation of zwitterionic polymer brushes on material surfaces is one of the most promising approaches. In this study, the photoreactive zwitterionic monomer 2-[2-(methacryloyloxy)ethyldimethylanmmonium] ethyl benzophenoxy phosphate (MBPP) was synthesized to improve the stability of zwitterionic polymer brushes. Although MBPP contains a benzophenone moiety in this molecule, it is water-soluble because of the zwitterionic linker. As a substrate, poly(ether ether ketone) (PEEK) was selected because it has recently been used to replace metals in orthopedic implants. Furthermore, PEEK is photosensitive, and UV graft polymerization of (meth)acrylic monomers on the surface can be performed without using any photoinitiators. Aqueous solutions containing various molar ratios of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and MBPP were prepared, and the PEEK specimens were immersed in these solutions. UV light was used to irradiate the solutions for 180 min, and the formation of grafting layers of zwitterionic polymers on PEEK specimens was confirmed using contact angle measurement and X-ray photoelectron spectroscopy. The surface friction of PEEK was effectively reduced via the photopolymerization of zwitterionic monomers. However, the surface lubricity of poly(MPC) (PMPC)-grafted surface deteriorated during continuous friction because of the removal of PMPC from the surface. Nevertheless, the stability of polymer brushes was effectively improved by adding only 0.5-0.75 mol % of MBPP in the monomer solution. Moreover, the reduction of wear on the surface was determined using confocal laser microscopy. The excellent lubrication phenomenon was attributed to preserving the hydration state of grafted polymers under compressive stress. Moreover, bacterial adhesion on substrates was tested and observed on a neat PEEK and scratched regions of uncross-linked PMPC-grafted PEEK. Note that bacterial adhesion was completely suppressed on the surface of PEEK modified with cross-linked PMPC brushes with MBPP. Thus, we conclude that the surface modification of PEEK with MPC and MBPP can provide ideal surface properties for orthopedic devices.
为了提高润滑性，在材料表面形成两性离子聚合物刷是最有前景的方法之一。在本研究中，合成了光反应性两性离子单体2-[2-(甲基丙烯酰氧基)乙基二甲基铵]乙基二苯甲酰氧基磷酸酯(MBPP)，以提高两性离子聚合物刷的稳定性。尽管MBPP分子中含有二苯甲酮部分，但由于两性离子连接基，它是水溶性的。作为基材，选择了聚醚醚酮(PEEK)，因为它最近被用于替代骨科植入物中的金属。此外，PEEK是光敏性的，(甲基)丙烯酸单体在其表面的紫外光接枝聚合可以在不使用任何光引发剂的情况下进行。制备了含有不同摩尔比的2-(甲基丙烯酰氧基)乙基磷酰胆碱(MPC)和MBPP的水溶液，并将PEEK试样浸入这些溶液中。用紫外光照射溶液180分钟，通过接触角测量和X射线光电子能谱确认了PEEK试样上两性离子聚合物接枝层的形成。通过两性离子单体的光聚合有效地降低了PEEK的表面摩擦力。然而，聚(MPC)(PMPC)接枝表面的表面润滑性在连续摩擦过程中由于PMPC从表面的去除而恶化。尽管如此，通过在单体溶液中仅添加0.5-0.75 mol%的MBPP，有效地提高了聚合物刷的稳定性。此外，使用共聚焦激光显微镜测定了表面磨损的减少情况。优异的润滑现象归因于在压缩应力下保持接枝聚合物的水合状态。此外，还测试了细菌在基材上的粘附情况，并在纯PEEK以及未交联的PMPC接枝PEEK的划痕区域进行了观察。请注意，在含有MBPP的交联PMPC刷修饰的PEEK表面，细菌粘附被完全抑制。因此，我们得出结论，用MPC和MBPP对PEEK进行表面改性可以为骨科器械提供理想的表面性能。
