Preparation And Properties Of Eletrospun3-hydroxybutyrate-co-3-hydroxyhexanoate(PHBHHx) For Small-diameter Vascular Graft

According to the Report Cardiovascular Disease In China(2012),there are some dangerous factors which cause cardiovascular disease in China.The death rate that people die from cardiovascular disease rank first among death causes,of which rural district accounts for 38.7%and 41.1% in urban district.In China nearly one person dies from cardiovascular disease in one second time.Because of the limitation of allografts and xenografts in clinical utility,development of vascular grafts has been the most efficient way for transplanting vascular graft and attracting much attention.Therefore,the study on preparation of vascular graft is of great significance.Poly(3-hydroxybutyrate-co-3-hydroxhexanoate)(short as PHBHHx) is one of newly popular biomaterials in recent years.It is the third-generation product generated by Polyhydroxyalkanoates(PHAs). PHAs,a class f naturally occurring biodegradable copolyesters with good general biocompatibility,are produced by a wide variety of different microorganisms.PHBHHx consists mainly of 3-HB(3-hydroxybutyate) and partially of3-HHx(3-hydroxyhexanoate).This polymer shows higher break strength and flexibility than PHBV,greater higher biocompatibility and hemocompatibility,and high affinity to a variety of cells,which makes it even more advantageous for medical sutures application.Through electrospinning technology,we plan to explore the feasibility of PHBHHx in the field of vascular graft.We investigated the electrospun process parameters,such as solvent 、the concentration of solution、voltage 、feeding speed 、receiving distance and research environment like temperature and relative humidity.PHBHHx was dissoluble in the mixture of CH2Cl2 and DMF.After lots of trials,we finally find the best parameters for electrospun process.With the suitable proportion of CH2Cl2 and DMF at 99/1,the PHBHHx nanofibers were obtained with thedistance between the needle tip and the collector 20 cm,voltage at 14 kV, flow rates of the solution at 1.0 ml/h, and temperature at 40℃ under the 40% relative humidity.Based on the optimized eletrospun parameters,we managed to make 6mm-diameter vascular graft including straight types and corrugated ones.Then they were evaluated in vitro for their performance which include tubular width、configuration 、mechanical properties、water permeability and dynamic radical compliance comparison with business vascular grafts.Through comprehensive test and analysis,it proved that 7h was most suitable time for receiving fibers.It proved that the thickness of the prepared vascular graft under 7h receiving time is 284.70 ±11.45μm and it showed a better mechanical performance than that of the commercial SW-ePTFE.Furthermore,this paper studied the blood compatibility and cytotoxicity properties.The test result showed that the hemolysis ratio was 0.46% which is much better than the medical standard for vascular graft and cell activity reached as high as 89% which means low or even no toxicity to cells.In summary,electropsun PHBHHx vascular graft showed amazing bio-property、water permeability with good mechanical properties than business vascular graft.This research will lay a basic foundation for the following vascular graft.