Cytocompatibility with osteogenic cells and enhanced in vivo anti-infection potential of quaternized chitosan-loaded titania nanotubes

Infection is one of the major causes of failure of orthopedic implants. Our previous study demonstrated that nanotube modification of the implant surface, together with nanotubes loaded with quaternized chitosan （hydroxypropyltrimethyl ammonium chloride chitosan, HACC）, could effectively inhibit bacterial adherence and biofilm formation in vitro. Therefore, the aim of this study was to further investigate the in vitro cytocompatibility with osteogenic cells and the in vivo anti-infection activity of titanium implants with HACC-loaded nanotubes （NT-H）. The titanium implant （Ti）, nanotubes without polymer loading （NT）, and nanotubes loaded with chitosan （NT-C） were fabricated and served as controls. Firstly, we evaluated the cytocompatibility of these specimens with human bone marrow-derived mesenchymal stem cells in vitro. The observation of cell attachment, proliferation, spreading, and viability in vitro showed that NT-H has improved osteogenic activity compared with Ti and NT-C. A prophylaxis rat model with implantation in the femoral medullary cavity and inoculation with methiciUin-resistant Staphylococcus aureus was established and evaluated by radiographical, microbiological, and histopathological assessments. Our in vivo study demonstrated that NT-H coatings exhibited significant anti-infection capability compared with the Ti and NT-C groups. In conclusion, HACC-loaded nanotubes fabricated on a titanium substrate show good compatibility with osteogenic cells and enhanced anti-infection ability in vivo, providing a good foundation for clinical application to combat orthopedic implant-associated infections.

Hemodynamic evaluation of different stent graft schemes in aortic arch covered stent implantation

Implantation of the left subclavian artery(LSA)stent graft used in fenestration technique of the thoracic endovascular aortic repair(TEVAR)may interfere with the aortic helical blood flow that is believed to have important protective functions against atherogenesis.The present study investigated four different LSA stent graft implantation schemes for their resulted blood flow patterns in the thoracic aortic with hemodynamic computational simulation methods:the flush branch(FB),the protruding branch(PB),the straight cuff branch(SCB)and the cured cuff branch(CCB).The results showed that the PB scheme could slightly enhance helicity of the swirling flow in the aorta,but the other three schemes had less effect on blood flow helicity.The PB scheme produced lowTAWSS,high-OSI and high-RRT around the LSA root,and the FB scheme had similar TAWSS,OSI and RRT in both value and distribution to those in the aorta without LSA stent graft implantation.The SCB and CCB schemes led to less area of high-OSI and high-RRT values along the walls of the LSA branch arteries.The results also showed that the PB scheme would significantly reduce blood supply to the LSA,on the contrary,the CCB scheme enhanced LSA blood supply and less effect on the total blood supply to the three branches of the thoracic aorta.In summary,all of the four schemes have no significant effect on the aortic swirling flow,however,in the terms of TAWSS,OSI,RRT and blood supply to the LSA,the CCB model might be the best option with less area of low-WSS,high-OSI,high-RRT and well blood supply in the LSA.

An in vivo study on the effect of coating stability on osteointegration performance of collagen/hyaluronic acid multilayer modified titanium implants

Aseptic loosening of implant is one of the main causes of Ti-based implant failure.In our previous work,a novel stable collagen/hyaluronic acid(Col/HA)multilayer modified titanium coatings(TCs)was developed by layer-by-layer(LBL)covalent immobilization technique,which showed enhanced biological properties compared with TCs that were physically absorbed with Col/HA multilayer in vitro.In this study,a rabbit model with femur condyle defect was employed to compare the osteointegration performance of them.Results indicated that Col/HA multilayer with favourable stability could better facilitate osteogenesis around implants and bone-implant contact.The Col/HA multilayer covalentimmobilized TC may reduce aseptic loosening of implant.

De novo strategy with engineering a multifunctional bacterial cellulose-based dressing for rapid healing of infected wounds

The treatment and healing of infected skin lesions is one of the major challenges in surgery.To solve this problem,collagen I(Col-I)and the antibacterial agent hydroxypropyltrimethyl ammonium chloride chitosan(HACC)were composited into the bacterial cellulose(BC)three-dimensional network structure by a novel membrane-liquid interface(MLI)culture,and a Col-I/HACC/BC(CHBC)multifunctional dressing was designed.The water absorption rate and water vapor transmission rate of the obtained CHBC dressing were 35.78±2.45 g/g and 3084±56 g m^(-2)⋅day^(-1),respectively.The water retention of the CHBC dressing was significantly improved compared with the BC caused by the introduced Col-I and HACC.In vitro results indicated that the combined advantages of HACC and Col-I confer on CHBC dressings not only have outstanding antibacterial properties against Staphylococcus aureus(S.aureus)compared with BC and CBC,but also exhibit better cytocompatibility than BC and HBC to promote the proliferation and spread of NIH3T3 cells and HUVECs.Most importantly,the results of in vivo animal tests demonstrated that the CHBC dressings fully promoted wound healing for 8 days and exhibited shorter healing times,especially in the case of wound infection.Excellent skin regeneration effects and higher expression levels of collagen during infection were also shown in the CHBC group.We believe that CHBC composites with favorable multifunctionality have potential applications as wound dressings to treat infected wounds.