Evaluations Of Degradation Procedures Of PPDO With High Molecular Weights In Vitro And A New Ppdo Made Biodegradable Setnt In Vivo

Background Biodegradable esophageal stents may be an alternative option for the treatment of refractory benign esophagus strictures.It is very important to design a new biodegradable esophageal stent with satisfactory outcomes.In this study,we applied polydioxanone monofilaments with high molecular weights for in vitro degradation.A a polydioxanone monofilaments knitted biodegradable esophageal stent with a segmented trunk and a modified stent fully covered with poly-L-lactic acid membrane in porcine models were used for in vivo evaluations.Objectives 1.To access the degradation of PPDO monofilaments with high molecular weights at different p H values.Key points and steps in degradation were analyzed.2.To evaluate the biodegradation procedures and complications of fully-covered biodegradable stents in vivo.Degradation procedures were analyzed.CBC count,liver and renal function test were performed.Methods 1.Degradation of PPDO monofilaments were performed at different p H values.Water absorption,weight loss rate,tensile test,FTIR spectroscopy and scanning electron microscopy were detected.2.Fully-covered biodegradable stents were achieved by covering PLLA membrane.The degradation procedures,complications of fully-covered stents were evaluated in porcine esophagus models.CBC count,liver and renal function test were performed.Results1.PPDO degradation rate was fast in p H=1.2 group,and kept slow and more steady in p H=7.4 and 8.5 groups 2.PPDO presented non-linear degradation procedures with a decreased tensile strength in a neutral and an alkaline environment.Degradation was slow at the early stage and fast at the late stage.3.No new chemical bonds formation was detected during PPDO degradation.4.Behaviors of pigs were not affected after stents insertion.Stents degraded after stents transplantation.The migration rate was low.No hemorrhage,perforation,ulcer,fistula and mucosal tearment were present.There was early elevation of neutrophils by CBC count.No changes of liver and renal functions were showed.Conclusions 1.PPDO monofilament with high molecular weights can be a candidate for biodegradable stent,for a good degradation procedure and a steady tensile strength during degradation.2.Biodegradable esophageal stents were with a good ability of self-biodegradation in vivo.The fully-covered biodegradable esophageal stents were with good safety due to a low stents migration rate and no incidence of severe complication.