Fabrication And Biological Function Of EPTFE Small Diameter Artificial Blood Vessel

Cardiovascular diseases plague human healthand become the first health killer of human beings.It causes about 160 billion US dollars in economic expenditure and 17 million deaths worldwide every year.In China,there are about 230 million patients with cardiovascular and cerebrovascular diseases.Due to their high prevalence,disability,and mortality,they seriously threaten people’s health.Vascular transplantation is currently the main treatment method.It has achieved good results in large diameter blood vessels(greater than 6 mm),but in the field of small diameter blood vessels(SDBV,less than 6 mm),due to thrombus,high mechanical compatibility,and long-term stability are required,there are no artificial blood vessels that can be used for transplantation in the world clinically.Autograft transplantation was successfully adopted clinically,however,it will increase the patient’s limb pain.More importantly,30%of patients have no effective donor due to health conditions or previous autograft transplantation.Therefore,the development of transplantable SDBV was urgent and have important practical significance.As a large diameter artificial blood vessel,ePTFE has good biocompatibility and mechanical properties,long-term serviceability and stability in clinic.Therefore,PTFE is still one of the candidate materials for SDBV.In recent years,ePTFE combined with in vitro iPS differentiation technology was first proposed by the Thomson team of the University of Wisconsin-Madison for the first time.Since both PTFE materials and iPS differentiation technology have been approved by the FDA,it will accelerate the application of ePTFE as a SDBV.However,the limited function of ePTFE cannot meet the needs of SDBV,such as platelet adhesion,restenosis,thrombus,and incomplete endothelialization.Therefore,it is necessary to modify ePTFE,including,preparation,modification,and biological functions.In this paper,a series of researches on ePTFE preparation,surface modification,functional construction,and intelligent regulation are carried out along the "processingoptimization-biological full-functionalization" mentality,so as to build a biologically functional ePTFE SDBV.The main work is divided into the following four parts:The first part is the green preparation of ePTFE.In order to solve the problem of biotoxicity of lubricants during the processing of traditional ePTFE,a new type of green lubricant was first developed.Alcohols were used as lubricants to prepare PTFE,and traditional Isopar G was used as control group.Meanwhile,a set of ePTFE preparation molds,including preforming,extrusion,and extrusion were developed.By combining with 300 kN stretcher and temperature temperature machines,1.6-6 mm of ePTFE SDBV were fabricated.Then,based on the new lubricant alcohol,the process parameters(expansion ratio,stretching speed,and expansion temperature)were studied through the optimization of ePTFE structure(node ratio),morphology(porosity,fiber length),and effect of mechanical properties.By comparing with commercial products,it was found that the green ePTFE products completely covered the existing commercial products in terms of structure and performance,and had better biological safety.This part of the work innovatively developed a new lubricant,solved the green preparation of ePTFE SDBV,and established the relationship between process parameters and morphology in detail.The second part is the coating preparation and release behavior of nitric oxide(NO)on ePTFE blood vessels.In order to solve the defects of single ePTFE with low cell adhesion ability,superhydrophobicity,and thrombosis,the functionalized surface modification of ePTFE was improved.First,ePTFE was treated with O2 plasma to introduce-OH to improve its hydrophilicity.Then dopamine was used to construct a mussel inspired biomimetic coating to improve the adhesion ability,and then dopamine and SeCA with different molar ratios were coated.On the surface of ePTFE,the catalytic carrier SeCA is effectively encapsulated in the polydopamine network.Under the catalysis of RSNO and GSH,NO was released for a long time,and the release period reached 35 days,the release amount was controllable at the range of1.2 to 4.2 μM.HUVECs culture results showed that the endothelial layer was formed on the 10th day.In vitro platelet adhesion tests also proved that NO can effectively inhibit platelet adhesion.And the results of in vitro thrombosis tests show that NO can effectively inhibit the formation of thrombus.The third part is in situ drug loading of ePTFE SDBV.In order to improve the disadvantages of the surface modification method,in situ constructing biofunctional ePTFE SDBV was developed.Specifically,a 70%alcohol solution was used as a lubricant for processing ePTFE,and three commonly used macromolecules,RGD,heparin,and SeCA,are respectively dissolved in 70%alcohol(traditional lubricants cannot be achieved).After expanding at 40℃,functionalized ePTFE were obtained.The results showed that the contact angle was reduced to 60°.Importantly,biological functions are effectively expressed,such as promoting cell adhesion and inhibiting platelet adhesion.Also,HUVECs can form a relatively complete endothelial layer.According to the characterization results of CD31,the complete endothelial layer presents clear boundaries,which further proves the in vitro functional vascular endothelial layer.The fourth part is the fabrication of smart ROS responsive ePTFE SDBV.The ROS response mechanism is that the initiator of thrombosis activates the release of thrombolytic drugs,and achieves in situ elimination of thrombus.Herein,we first synthesized ROS responsive drugs,including the ESA,the response unit oxalyl chloride,and the mPEG.Then the ROS drug and PCL were dissolved in chloroform,then the PCL/drug matrix was encapsulated in the ePTFE material body,after that,the ePTFE SDBV with intelligent thrombolytic ability was obtained.NMR and FTIR results indicate successful synthesis,preparation,and loading of drugs into ePTFE samples.The release behavior proved the intelligent ROS(H2O2)response release ability.The platelet adhesion,in vtro thrombosis,and HUVECs culture tests indicated the ePTFE grafts with ROS response performance can effectively prohibit platelet adhesion,inhibit the formation of thrombus,and promote the uniform growth of HUVECs.Therefore,the smart ROS responsive ePTFE SDBV exhibit diverse biological functions and show great prospects for clinical application.