For the surgical treatment of cardiovascular disease(CVD),there is a clear and unmet need in developing small-diameter(diameter<6 mm)vascular grafts.In our previous work,sulfated silk fibroin(SF)was successfully fabricated as a potential candidate for preparing vascular grafts due to the great cytocompatibility and hemocompatibility.However,vascular graft with single layer is difficult to adapt to the complex internal environment.In this work,polycaprolactone(PCL)and sulfated SF were used to fabricate bilayer vascular graft(BLVG)to mimic the structure of natural blood vessels.To enhance the biological activity of BLVG,nicorandil(NIC),an FDA-approved drug with multi-bioactivity,was loaded in the BLVG to fabricate NIC-loaded BLVG.The morphology,chemical composition and mechanical properties of NIC-loaded BLVG were assessed.The results showed that the bilayer structure of NIC-loaded BLVG endowed the graft with a biphasic drug release behavior.The in vitro studies indicated that NIC-loaded BLVG could significantly increase the proliferation,migration and antioxidation capability of endothelial cells(ECs).Moreover,we found that the potential biological mechanism was the activation of PI3K/AKT/eNOS signaling pathway.Overall,the results effectively demonstrated that NIC-loaded BLVG had a promising in vitro performance as a functional small-diameter vascular graft.
Zheng XingChen ZhaoChunchen ZhangYubo FanHaifeng Liu
Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament（ACL）reconstruction.Interference screw,as a surgical implant in ACL reconstruction,may influence natural loading transmission and contribute to tunnel enlargement.The aims of this study are（1）to quantify the alteration of strain energy density（SED）distribution after the anatomic single-bundle ACL reconstruction;and（2）to characterize the influence of screw length and diameter on the degree of the SED alteration.A validated finite element model of human knee joint was used.The screw length ranging from 20 to 30 mm with screw diameter ranging from 7 to 9 mm were investigated.In the post-operative knee,the SED increased steeply at the extra-articular tunnel aperture under compressive and complex loadings,whereas the SED decreased beneath the screw shaft and nearby the intra-articular tunnel aperture.Increasing the screw length could lower the SED deprivation in the proximal part of the bone tunnel;whereas increasing either screw length or diameter could aggravate the SED deprivation in the distal part of the bone tunnel.Decreasing the elastic modulus of the screw could lower the bone SED deprivation around the screw.In consideration of both graft stability and SED alteration,a biodegradable interference screw with a long length is recommended,which could provide a beneficial mechanical environment at the distal part of the tunnel,and meanwhile decrease the bone-graft motion and synovial fluid propagation at the proximal part of the tunnel.These findings together with the clinical and histological factors could help to improve surgical outcome,and serve as a preliminary knowledge for the following study of biodegradable interference screw.
Jie YaoGuan-Ming KuangDuo Wai-Chi WongWen-Xin NiuMing ZhangYu-Bo Fan
The woodpecker does not suffer head/eye impact injuries while drumming on a tree trunk with high acceleration （more than 1000xg） and high frequency. The mechanism that protects the woodpecker＇s head has aroused the interest of ornithologists, biologists and scientists in the areas of mechanical engineering, material science and electronics engineering. This article reviews the literature on the biomechanisms and materials responsible for protecting the woodpecker from head impact injury and their applications in engineering and human protection.
A significant limitation in the engineering of artificial small-diameter vascular scaffolds is that the number of endothelial cells(ECs)is not sufficient to generate a confluent coverage of the vascular scaffolds,so that the surfaces of vascular scaffolds form thrombus via platelet adhesion and aggregation.Thrombus decrease relies on three-dimensional(3D)scaffolds to mimic the natural extracellular matrix(ECM)as templates to regulate cell behavior and facilitate tissue maturation.Here,we developed 3D scaffolds consisting of silk fibroin(SF)nanofibers and homogeneous microspheres by electrospinning and microfluidics.The nanofibers with diameters ranging from 250 to 350 nm doped with microspheres(2–10μm)formed bridge-shaped structures.ECs were seeded and maintained on the 3D microsphere-nanofiber scaffolds with a mean fiber diameter of 300 nm.A 10%higher ratio of cell proliferation on 3D microsphere-nanofiber SF scaffolds was noted as compared to that on microporous and sponge-like SF scaffolds with small surface network fabricated by freeze-drying.Moreover,the gene transcript levels including CD146,VE-C and PECAM-1 were better preserved on 3D microsphere-nanofiber SF scaffolds than those on freeze-dried scaffolds.Thus,the developed 3D microsphere-nanofiber structure may have a myriad of applications in vascular tissue engineering scaffolds and cardiovascular devices.
Qiang LiuGuoliang YingNan JiangAli KYetisenDanyu YaoXiaoying XieYubo FanHaifeng Liu
