Objective: To develop dexamethasone plus minocycline-loaded liposomes (Dex/Mino liposomes) and apply them to improve bioinert polyetheretherketone (PEEK) surface, which could prevent post-operative bacterial contamination, enhance ossification for physiologic osseointegration, and finally reduce implant failure rates.
Methods: Dex/Mino liposomes were covalently grafted onto the PEEK surface using polydopamine (pDA) coating as a medium. Confocal laser scanning microscopy was used to confirm the binding of fluorescently labeled liposomes onto the PEEK substrate, and a microplate reader was used to semiquantitatively measure the average fluorescence intensity of fluorescently labeled liposome-decorated PEEK surfaces. Moreover, the mouse subcutaneous infection model and the beagle femur implantation model were respectively conducted to verify the bioactivity of Dex/Mino liposome-modified PEEK in vivo, by means of micro computed tomography (micro-CT) and hematoxylin and eosin (HE) staining analysis.
Results: The qualitative and quantitative results of fluorescently labeled liposomes showed that, the red fluorescence intensity of the PEEK-pDA-lipo group was stronger than that of the PEEK-NF-lipo group (P < 0.05); the liposomes were successfully and uniformly decorated on the PEEK surfaces due to the pDA coating. After mouse subcutaneous implantation of PEEKs for 24 hours, HE staining results showed that the number of inflammatory cells in the PEEK-Dex/Mino lipo group were lower than that in the inert PEEK group (P < 0.05), indicating a lower degree of infection in the test group. These results suggested that the Mino released from the liposome-functionalized surface provided an effective bacteriostasis in vivo. After beagle femoral implantation of PEEK for 8 weeks, micro-CT results showed that the PEEK-Dex/Mino lipo group newly formed more continuous bone when compared with the inert PEEK group; HE staining results showed that more new bones were formed in the PEEK-Dex/Mino lipo group than in the inert PEEK group, which were firmly bonded to the functionalized PEEK surface and extended along the PEEK interface. These results suggested that the Dex released from the liposome-functionalized surface induced effective bone regeneration in vivo.
Conclusion: Dex/Mino liposome modification enhanced the bioactivity of inert PEEK, the functionalized PEEK with enhanced antibacterial and osseointegrative capacity has great potential as an orthopedic/dental implant material for clinical application.
目的: 制备地塞米松/米诺环素(dexamethasone/minocycline，Dex/Mino)脂质体(liposome，lipo)修饰的聚醚醚酮(polyetheretherketone，PEEK)，探究功能化PEEK在体内应用时是否能有效预防感染且促进新骨再生，实现生理骨整合。
方法: 利用聚多巴胺(polydopamine，pDA)涂层作中间介质，将Dex/Mino脂质体修饰到PEEK表面，通过荧光脂质体接枝进行定性和定量检测，评价脂质体是否成功共价修饰在该表面。分别建立小鼠皮下植入感染模型和比格犬股骨植入模型，通过Micro-CT及苏木精-伊红(hematoxylin-eosin，HE)染色分析，评价Dex/Mino脂质体修饰的PEEK的体内生物活性。
结果: 荧光脂质体接枝定性和定量结果显示，pDA功能化修饰组的红色荧光强度强于非功能化修饰组(P < 0.05)，由于pDA涂层的存在，脂质体成功接枝于PEEK表面并在其表面均匀分布。小鼠皮下PEEK片植入24 h后，HE染色结果显示，与纯PEEK组相比，PEEK-Dex/Mino lipo组的炎性细胞数量较低(P < 0.05)，即感染程度较低，提示脂质体中Mino的释放在体内能有效地预防感染。比格犬股骨植入8周后，Micro-CT和HE染色结果显示，在PEEK-Dex/Mino lipo组中，新骨形成比纯PEEK组多，且牢固地结合在功能化修饰的PEEK表面，沿着PEEK界面延伸，提示脂质体中Dex的释放在体内有效地刺激和引导了新骨再生。
结论: Dex/Mino脂质体修饰提高了惰性PEEK的生物活性，功能化PEEK具有增强的骨整合能力(预防感染和促进新骨再生)，其作为牙科/骨科替代修复材料极具临床应用前景。
Keywords: Bacteriostasis; Dexamethasone; Liposomes; Minocycline; Osseointegration; Polyetheretherketone.