In vivo study on heparin/poly-L-lysine-copper coating for surface functionalization of ureteral stent

Polyurethane(PU)ureteral stents are used in clinics to maintain the ureteral patency.Due to biofilm formation and encrustation complications,long-term clinical usage has been limited.It is therefore necessary to develop an effective response to this unmet medical need.A heparin/poly-L-lysine/copper(NPs)coating was developed in our previous work that showed the effect of preventing infection and encrustation in vitro.In this work,a further study was conducted by grafting NPs on clinical ureteral stents that then were implanted into the infectious bladders of Wistar rats to investigate the effects of nanoparticles on bacterial growth and crystal deposition in vivo.It was found that decreased numbers of adherent microbes,urease amount splitting by bacteria,and deposited crystals were observed on the NPs stents with significant differences in comparison with PU stents.Besides,histological analysis showed that the NPs stents decreased the host tissue inflammation in close relation to the decrease biofilm formation and encrustation after 28 days of implantation.

Degradation and biological properties of Ca-P contained micro-arc oxidation self-sealing coating on pure magnesium for bone fixation

Poor corrosion resistance is one of the main disadvantages for biodegradable magnesium-based metals,especially applied for bone fixation,where there is a high demand of bio-mechanical strength and stability.Surface coating has been proved as an effective method to control the in vivo degradation.In this study a Ca-P self-sealing micro-arc oxidation(MAO)coating was studied to verify its efficacy and biological properties by in vitro and in vivo tests.It was found that the MAO coating could effectively retard the degradation according to immersion and electrochemical tests as well as 3D reconstruction by X-ray tomography after implantation.The MAO coating exhibited no toxicity and could stimulate the new bone formation.Therefore,the Ca-P self-sealing MAO coating could be a potential candidate for application of biodegradable Mg-based implant in bone fixations.

Design and preparation of polyurethane-collagen/ heparin-conjugated polycaprolactone double-layer bionic small-diameter vascular graft and its preliminary animal tests

Background People recently realized that it is important for artificial vascular biodegradable graft to bionically mimic the functions of the native vessel. In order to overcome the high risk of thrombosis and keep the patency in the clinical small-diameter vascular graft （SDVG） transplantation, a double-layer bionic scaffold, which can offer anticoagulation and mechanical strength simultaneously, was designed and fabricated via electrospinning technique. Methods Heparin-conjugated polycaprolactone （hPCL） and polyurethane （PU）-collagen type I composite was used as the inner and outer layers, respectively. The porosity and the burst pressure of SDVG were evaluated. Its biocompatibility was demonstrated by the 3-（4,5-dimethyl-2-thiazol）-2,5-diphenyl-2H tetrazolium bromide （MTT） test in vitro and subcutaneous implants in vivo respectively. The grafts of diameter 2.5 mm and length 4.0 cm were implanted to replace the femoral artery in Beagle dog model. Then, angiography was performed in the Beagle dogs to investigate the patency and aneurysm of grafts at 2, 4, and 8 weeks post-transplantation. After angiography, the patent grafts were explanted for histological analysis. Results The double-layer bionic SDVG meet the clinical mechanical demand. Its good biocompatibility was proven by cytotoxicity experiment （the cell＇s relative growth rates （RGR） of PU-collagen outer layer were 102.8%, 109.2% and 103.5%, while the RGR of hPCL inner layer were 99.0%, 100.0% and 98.0%, on days 1, 3, and 5, respectively） and the subdermal implants experiment in the Beagle dog. Arteriography showed that all the implanted SDVGs were patent without any aneurismal dilatation or obvious anastomotic stenosis at the 2nd, 4th, and 8th week after the operation, except one SDVG that failed at the 2nd week. Histological analysis and SEM showed that the inner layer was covered by new endothelial-like cells. Conclusion The double-layer bionic SDVG is a promising candidate as a replacement of native small-diameter vascular graft.