Study On Properties And Preparation Method Of Biodegradable Polymer Stent Coating

Due to its natural biocompatibility and biodegradability,biodegradable polymer(BP)stents have been widely developed and applied as the main way to treat vascular stenosis.However,compared with metal materials,polymer materials still have insufficient mechanical properties.Therefore,improving the mechanical properties of biodegradable polymer scaffolds has become an important research direction.Coatings,as conventional drug carriers,play an important role in controlling drug release in the treatment of lesions.With the deepening of research,BP coatings have been found to have the potential to improve the mechanical properties of BP stents.This paper mainly takes poly(Llactide)(PLLA)engraved stent and PLLA braided stent as the objects,analyzes the effect of coating on the mechanical properties of the two.On the one hand,the effect of poly(D,L-lactide)(PDLLA)/ poly(L-lactide-glycolide)(PLGA)blend coating on the mechanical properties of PLLA engraved stent was explored;On the other hand,the effect of six-arm poly(L-lactide-co-ε-caprolactone)(6SPLCL)/ hexamethylene diisocyanate(HDI)cross-linked coating on the mechanical properties of PLLA braided stent was explored.The main contents and results are as follows:(1)It is proposed to apply BP coating to improve the mechanical properties of stents to solve the problem of insufficient mechanical properties of BP stents due to differences in material properties.Firstly,the restrictive factor of the mechanical properties of polymer vascular stents is the difference in material properties,and the research status of improving the mechanical properties of vascular stents is summarized.At the same time,the main functions of polymer coatings are analyzed,and the application of polymer coatings to improve mechanical properties of vascular stents is proposed.(2)The coating preparation process and detection method were determined,and related experimental equipment was built.Through comparative analysis of various coating materials and coating preparation methods,according to the structural characteristics of engraved stents and braided stents,it is proposed to use ultrasonic atomization spraying to prepare stent coatings,and related spraying equipment was built.Aiming at the detection and evaluation of stent coating,the treatment method and equipment,observation method and equipment,and mechanical property detection method and equipment of coated stent are given.(3)The PDLLA/PLGA blend coating was proposed as a means of improving the mechanical properties of PLLA engraved stents(balloon-expandable),which increased the maximum peak force and radial stiffness by 6.53% and 0.47%,respectively,compared with uncoated stents..By analyzing the structural characteristics of PLLA engraved stents and the compression and expansion during implantation,it is proposed to enhance the mechanical properties of PLLA engraved stents by blending coatings.The results showed that the coating with a mass ratio of 80/20 significantly improved the mechanical properties of the engraved stent after compression and expansion compared with other ratio coatings,and the maximum peak force and radial stiffness of which increased by 6.53% and 0.47% respectively compared with the uncoated stent.(4)It is proposed to use the super-elastic coating as the coating of the PLLA braided stent(self-expanding type),which greatly improves the mechanical properties of the PLLA braided stent,among which the radial resilience is increased by 236.7%.By analyzing the deformation characteristics of PLLA braided scaffolds during self-expansion and release during implantation,it is proposed to enhance the mechanical properties of PLLA braided stent by restricting the movement of monofilaments at the braided intersections by cross-linked super-elastic coatings.The method can greatly improve the mechanical properties of the PLLA braided stent.When the mass ratio of the cross-linked coating is 5:1,it has sufficient toughness and Young’s modulus to maximize the reinforcement effect and increase the radial resilience by 236.7%.In conclusion,different coating preparation strategies were adopted in this paper to enhance the mechanical properties of PLLA engraved stent and PLLA braided stent,which has positive significance for the effect of extended coating on vascular stents.