Surface modification of vascular endothelial growth factor-loaded silk fibroin to improve biological performance of ultra-high-molecular-weight polyethylene via promoting angiogenesis

Ultra-high-molecular-weight polyethylene (UHMWPE) has been applied in orthopedics, as the materials of joint prosthesis, artificial ligaments, and sutures due to its advantages such as high tensile strength, good wear resistance, and chemical stability. However, postoperative osteolysis induced by UHMWPE wear particles and poor bone-implant healing interface due to scarcity of osseointegration is a significant problem and should be solved imperatively. In order to enhance its affinity to bone tissue, vascular endothelial growth factor (VEGF) was loaded on the surface of materials, the loading was performed by silk fibroin (SF) coating to achieve a controlled-release delivery. Several techniques including field emission scanning electron microscopy (FESEM) and attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) and water contact angle measurement were used to validate the effectiveness of introduction of SF/VEGF. The result of ELISA demonstrated that the release of VEGF was well maintained up to 4 weeks. The modified UHMWPE was evaluated by both in vitro and in vivo experiments. According to the results of FESEM and cell counting kit-8 (CCK-8) assay, bone marrow mesenchymal stem cells cultured on the UHMWPE coated with SF/VEGF and SF exhibited a better proliferation performance than that of the pristine UHMWPE. The model rabbit of anterior cruciate ligament reconstruction was used to observe the graft-bone healing process in vivo. The results of histological evaluation, microcomputed tomography (micro-CT) analysis, and biomechanical tests performed at 6 and 12 weeks after surgery demonstrated that graft-bone healing could be significantly improved due to the effect of VEGF on angiogenesis, which was loaded on the surface by SF coating. This study showed that the method loading VEGF on UHMWPE by SF coating played an effective role on the biological performance of UHMWPE and displayed a great potential application for anterior cruciate ligament reconstruction.