Antimicrobial Expanded Polytetrafluoroethylene Film Prepared by 3-ray Radiation Induced Grafting of Poly（acrylic acid）

The simultaneous γ-ray-radiation-induced grafting polymerization of acrylic acid on ex- panded polytetrafluoroethylene （ePTFE） film was investigated. It was found that the degree of grafting （DG） of poly（acrylic acid） （PAA） can be controlled by the monomer concentration, absorbed dose, and dose rate under an optimal inhibitor concentration of [Fe2＋]=18 mmol/L. SEM observation showed that the macroporous structure in ePTFE films would be covered gradually with the increase of the DG of PAA. The prepared ePTFE-g-PAA film was im- mersed in a neutral silver nitrate solution to fabricate an ePTFE-g-PAA/Ag hybrid film after the addition of NaBH4 as a reduction agent of Ag＋ to Ag atom. SEM, XRD, and XPS results proved that Ag nanoparticles with a size of several tens of nanometers to 100 nanometers were in situ immobilized on ePTFE film. The loading capacity of Ag nanoparticles could be tuned by the DG of PAA, and determined by thermal gravimetric analysis. The quart- titative antibacterial activity of the obtained ePTFE-g-PAA/Ag hybrid films was measured using counting plate method. It can kill all the Escherichia coli in the suspension in 1 h. Moreover, this excellent antibacterial activity can last at least for 4 h. This work provides a facile and practical way to make ePTFE meet the demanding antimicrobial requirement in more and more practical application areas.

Effect of Expanded Polytetrafluoroethylene Combined with Autologous Ear Cartilage in Nasal Plastic Surgery

Objective:To explore the effect of combined application of expanded polytetrafluoroethylene and autologous ear cartilage in nasal plastic surgery.Methods:76 cases of nasal plastic surgery patients in our hospital from September 2019 to September 2020 were selected as the research objects and divided into experimental group(38 cases,treated with expanded polytetrafluoroethylene+autologous ear cartilage surgery)and control group(38 cases,treated with autologous ear cartilage surgery).The treatment effect,appearance score and complications were compared.Results:The total effective rate of the experimental group(97.37%,37/38)was higher than that of the control group(78.95%,30/38),P<0.05;After treatment,the appearance score of the experimental group was(8.97±0.37),which was significantly higher than that of the control group(P<0.05);The total incidence of complications in the experimental group(5.26%,2/38)was significantly lower than that in the control group(21.05%,8/38),P<0.05.Conclusion:In the process of nasal plastic surgery,the combined application of autologous ear cartilage surgery and expanded polytetrafluoroethylene has obvious effect,improves the appearance of patients,and has less postoperative complications,which is worthy of promotion.

Research and clinical translation of trilayer stent-graft of expanded polytetrafluoroethylene for interventional treatment of aortic dissection

The aortic dissection(AD)is a life-threatening disease.The transcatheter endovascular aortic repair(EVAR)affords a minimally invasive technique to save the lives of these critical patients,and an appropriate stent-graft gets to be the key medical device during an EVAR procedure.Herein,we report a trilayer stent-graft and corresponding delivery system used for the treatment of the AD disease.The stent-graft is made of nitinol stents with an asymmetric Z-wave design and two expanded polytetrafluoroethylene(ePTFE)membranes.Each of the inner and outer surfaces of the stent-graft was covered by an ePTFE membrane,and the two membranes were then sintered together.The biological studies of the sintered ePTFE membranes indicated that the stent-graft had excellent cytocompatibility and hemocompatibility in vitro.Both the stent-graft and the delivery system exhibited satisfactory mechanical properties and operability.The safety and efficacy of this stent-graft and the corresponding delivery system were demonstrated in vivo.In nine canine experiments,the blood vessels of the animals implanted with the stent-grafts were of good patency,and there were no thrombus and obvious stenosis by angiography after implantation for 6months.Furthermore,all of the nine clinical cases experienced successful implantation using the stent-graft and its postrelease delivery system,and the 1-year follow-ups indicated the preliminary safety and efficacy of the trilayer stent-graft with an asymmetric Z-wave design for interventional treatment.

Biaxial stretching of polytetrafluoroethylene in industrial scale to fabricate medical ePTFE membrane with node-fibril microstructure

Expanded polytetrafluoroethylene(ePTFE)is promising in biomedical fields such as covered stents and plastic surgery owing to its excellent biocompatibility and mechanical properties.However,ePTFE material prepared by the traditional biaxial stretching process is with thicker middle and thinner sides due to the bowing effect,which poses a major problem in industrial-scale fabrication.To solve this problem,we design an olive-shaped winding roller to provide the middle part of the ePTFE tape with a greater longitudinal stretching amplitude than the two sides,so as to make up for the excessive longitudinal retraction tendency of the middle part when it is transversely stretched.The as-fabricated ePTFE membrane has,as designed,uniform thickness and node-fibril microstructure.In addition,we examine the effects of mass ratio of lubricant to PTFE powder,biaxial stretching ratio and sintering temperature on the performance of the resultant ePTFE membranes.Particularly,the relation between the internal microstructure of the ePTFE membrane and its mechanical properties is revealed.Besides stable mechanical properties,the sintered ePTFE membrane exhibits satisfactory biological properties.We make a series of biological assessments including in vitro hemolysis,coagulation,bacterial reverse mutation and in vivo thrombosis,intracutaneous reactivity test,pyrogen test and subchronic systemic toxicity test;all of the results meet the relevant international standards.The muscle implantation of the sintered ePTFE membrane into rabbits indicates acceptable inflammatory reactions of our sintered ePTFE membrane fabricated on industrial scale.Such a medical-grade raw material with the unique physical form and condensed-state microstructure is expected to afford an inert biomaterial potentially for stent-graft membrane.

Handmade tri-leaflet ePTFE conduits versus homografts for right ventricular outflow tract reconstruction

Background This study aimed to investigate the performance of handmade tri-leaflet expanded polytetrafluoroethylene(ePTFE)conduits in the absence of a suitable homograft.Methods Patients who underwent right ventricular outflow tract reconstruction with tri-leaflet ePTFE conduits or homografts between December 2016 and August 2020 were included.The primary endpoint was the incidence of moderate or severe conduit stenosis(>36 mmHg)and/or moderate or severe insufficiency.The secondary endpoint was the incidence of severe conduit stenosis(>64 mmHg)and/or severe insufficiency.Results There were 102 patients in the ePTFE group and 52 patients in the homograft group.The median age was younger[34.5(interquartile range:20.8-62.8)vs.60.0(interquartile range:39.3-81.0)months,P=0.001]and the median weight was lower[13.5(10.0-19.0)vs.17.8(13.6-25.8)kg,P=0.003]in the ePTFE group.The conduit size was smaller(17.9±2.2 vs.20.5±3.0 mm,P<0.001)and the conduit Z score was lower(1.48±1.04 vs.1.83±1.05,P—0.048)in the ePTFE group.There was no significant difference in the primary endpoints(log rank,T3=0.33)and secondary endpoints(log rank,P=0.35).Multivariate analysis identified lower weight at surgery[P=0.01;hazard ratio:0.75;95%confidence interval(CI)0.59-0.94]and homograft conduit use(P=0.04;hazard ratio:8.43;95%CI 1.14—62.29)to be risk factors for moderate or severe conduit insufficiency.No risk factors were found for moderate or severe conduit stenosis or conduit dysfunction on multivariate analysis.Conclusion Handmade tri-leaflet ePTFE conduits showed acceptable early and midterm outcomes in the absence of a suitable homograft,but a longer follow-up is needed.

Photometric analysis of absorbable barbed suture for periareolar closure in mastopexy

Aim:The primary author previously described his technique for periareolar closure in mastopexy using a pinwheel interlocking purse string with absorbable barbed suture and now reports the results of a retrospective photometric analysis comparing this technique with the same closure using Gortex®suture.This study is designed to compare the degree of areolar widening and safety profile of using absorbable barbed sutures for periareolar closure versus permanent smooth suture.Methods:A retrospective chart review was conducted of all patients whose periareolar closures were performed using an interlocking purse-string technique over a 10-year period.Only patients undergoing circumvertical mastopexy were included.All had photometric evaluation and follow-up performed within 6-24 months.Results:In total,20 patients(40 areolas),which were closed with absorbable barbed suture,were analyzed photometrically.In this suture group,areola size increased a mean of 4.9%from baseline,and no complications(0%)were observed.This compared favorably with previously reported complication rates using permanent sutures and with a series of cases presented herein in which permanent smooth suture was used for purse string closure.The degree to which absorbable barbed suture controls areolar spread was shown to be significantly better than those where permanent smooth purse string techniques were employed.Conclusion:Circumvertical mastopexy closures using absorbable barbed suture was shown to be safe and effective and compared favorably to older techniques using permanent smooth suture for similar closures.This paper lends support to the safety of using absorbable barbed suture in circumareolar closures to limit areolar spread.