Design And Fabrication Of Silk/PET Small-diameter Vascular Grafts Without Preclotting

Vascular transplantation is an effective way to cure human’s vessel diseases. Large or medium diameter vascular grafts have been successfully applied in clinical for decades. However, varies of problems existed in the application of the small diameter arterial grafts. An ideal small-diameter vascular graft should have excellent mechanical properties, well-controlled inner diameter, thickness, proper water permeability values and good biocompatibility. Although plenty of research have been done both by domestic and foreign scholars in small calibre vascular grafts, there are still many problems to solve in the field of small diameter arterial prostheses.With easy-processing, excellent mechanical properties and controlled inner diameter and thickness, textile based vascular prostheses are considered as a potential suitable blood vessel replacement. But it is difficult to control the water permeability of the vascular graft and the balance between the diameter and the thickness. Therefore this study aimed at developing a silk-PET small diameter vascular graft (targeted inner diameter=4mm) using medical grade silk and PET as material with good mechanical properties, moderate thickness and proper water permeability. Finally the woven silk-PET seamless small diameter vascular graft with good performance overall avoiding preclotting was constructed on a transformed shuttle loom and obtained after degumming treatment.In this study a series of small diameter woven tubes were made by different weaving structures and different materials. Braided silk yams, with the density of204.5D and130.8D, and braided polyester (PET) yarns,179.0D and112.2D, were selected as warp yarns,100D PET and84.36D silk as weft yarns. Combining the selected yarns using structures of plain,2/2twill and1/3twill,18samples were obtained including6silk-PET samples,6pure silk prototypes as well as6pure PET ones. Some common problems have been solved in this study such as deckle tube edge and uniformity. The study also researched the after treatment of silk-based tubular fabrics in order to get the fibroin/PET small diameter vascular grafts. The results showed that the silk/PET tubular fabric could be degummed completely under the condition of0.05(wt)%Na2CO3solution at87℃for90min with mechanical washing despite of the different weaving structures. Finally the well-constructed silk fibroin-PET prototype grafts were obtained.Dimension including thickness, inner tube diameter, fabric tightness and silk coverage rate, mechanical properties including probe bursting strength and circumferential strength were tested in order to discover the relationship between wall structure and dimension or mechanical properties. The study also compared the samples with the commercial ePTFE small diameter vascular graft in mechanical properties. The results showed that16samples were selected except the two samples of SPT5and SST6. At last fibroin/PET small diameter vascular grafts with good mechanical properties and values of water permeability under300mL·cm-2·min-1had varies of silk coverage rates.By selecting the fiber materials, optimizing fabric structures and improving the forming technology of small-diameter vascular grafts, this study achieved the goal to fabricate the vascular grafts free of preclotting. The study is a building process for further developfhent of antithrombosis and endothelialization of silk-PET small vascular grafts.