3D分层纳米钛层层自组装人β-防御素3构建智能抗菌涂层抑制内植物感染的实验研究

Bone and joint infections, including chronic implant-related infection are refractory to treatment. The most important mechanism of chronic infection is the existence of bacterial biofilms and antibiotic-resistant bacterias which can evade most of antibiotics and the immune systems. Duo to their good mechanical properties and excellent biocompatibility，titanium has been widely used as hard tissue implants. However, there are still some disadvantages such as inadequate osteogenesis inducing ability and susceptibility to bacterial infection. First, our previous studies provided encouraging evidences that endogenous antibiotic polypeptides, human β-defensin-3（HBD-3）, activity against antibiotic-resistant biofilm cells, and biofilm-associated and methicillin-resistance genes. Our research group independently prepared and characterized three dimension (3D) hierarchical nanoporous on titanium surface, which showed good bioactivity. More importantly, this elaborately designed titanium surface can effectively inactivate the adherent S. aureus on surface by virtue of a contact-killing mode. Second, the designed titanium surface can significantly facilitate the initial adhesion and spreading behaviors of bone marrow mesenchymal stem cells on titanium. The results suggested that, the elaborately designed titanium surface might own a cell-favoring ability that can help mammalian cells win the initial adhesion race against bacteria. At last，We design the 3D hierarchical nanostructuring of titanium and the subsequent coating of resulting topographical features with an ultrathin tannic acid/HBD-3 antibacterial layer-by-layer film, that kill sessile bacteria but support stem cells adhesion and this modified surface can steadily release the antibacterial peptide HBD-3 in a self-defensive manner. As a consequence, the elaborate HBD-3-loaded surface demonstrated a powerful anti-bacterial and biofilm-resistant capability, modulated innate and adaptive immune responses without significant cytotoxicity. Therefore, the integration of HBD-3 onto titanium-based implant surface may be a hopeful tool to prevent implant-associated infections in the orthopaedic surgery.

内植物感染的治疗是困扰骨科医生的难题，迁延不愈的最主要机制包括细菌生物膜的形成及耐药菌的出现，从而逃避抗生素和体内的免疫机制。由于具有良好的机械性能和生物相容性，钛被广泛用作硬组织植入材料，但是尚有诱导骨组织修复的能力不足、抗菌性能差的缺陷。前期研究表明，内源性抗菌肽人β-防御素3对生物膜内耐药葡萄球菌的杀灭作用明显增强，抑制细菌成膜及耐药基因表达，并调控免疫应答。本项目首先构建3D分层二氧化钛纳米管，使上述钛表面具有良好的生物活性，能有效减少耐药金黄色葡萄球菌在表面黏附。其次，验证改性钛表面能够有效促进骨髓间充质干细胞的早期黏附和聚集。最后，通过钛表面已赋予的抗菌性能和细胞相容性，构建层层自组装构建单宁酸/人β-防御素3智能抗菌涂层以进一步增强钛表面的抗菌活性。钛表面的抗菌肽智能释放，体内体外抗菌效果满意，调控免疫应答，且无细胞毒性，并希望未来在预防和治疗假体周围感染有一定临床应用前景。

由于抗生素的滥用及耐药病原体的增加，感染仍是全球健康的主要威胁之一。特别是骨科手术中所涉及的内固定或人工关节置换术后，一旦机体局部免疫力下降，常伴随细菌在内植物表面黏附、生物膜形成、细菌内化、细菌耐药变异，继而逃避机体免疫应答。为此，我们拟通过纳米材料学、免疫学、微生物学等交叉研究手段，系统阐明新材料的本征结构对抗菌免疫识别、互作与应答的分子机制。我们制备的生物膜微环境响应型生物材料可以响应酸性环境释放抗菌药物。同时，材料也会参与感染微环境处的免疫调控，更好的清除内植物相关生物膜感染以及促进由感染引起的组织损伤的修复。本研究创新性的提出了的内植物晚期感染治疗的非抗生素治疗思路，并推动研究成果与临床需求紧密对接与转化。