In Vitro Dynamic Encrustation Simulator And Its Application In The Study Of Anti-encrustation Of Ureteral Stent

Long-term ureteral stent encrustation is an important factor leading to urinary system infection and other clinical complications.In vitro encrustation simulation can feedback the antiencrustation performance of scaffold materials and structures in time,but it is difficult to simulate the complex dynamics of micro-environment in vivo.Therefore,the design L of this project has developed an in vitro encrustation dynamic simulation device,which can be used to simulate the urinary flushing and ureter peristalsis,to evaluate the antiencrustation performance of ureter stent,and to optimize the preparation method of ureter stent,to improve the antiencrustation performance of braided Ni-Ti alloy ureteral stent.The main contents and findings of the study are as follows:(1)The design and preparation of a dynamic simulator for encrustation in vitro.Five major components,which are suitable for human anatomy and urodynamics,are designed,including pelvis simulation system,ureter simulation system,fluid delivery system,stress simulation system and flow monitoring system,first,the antiencrustation performance of the device was optimized,and then the repeatable performance of the device was verified,qualitative and quantitative characterization of the encrustation degree of the same batch of scaffolds after dynamic simulation of encrustation in vitro confirmed that the device had high repeatability and stable performance.(2)The comparative study between the dynamic simulation experiment and the static simulation experiment of encrustation in vitro.The dynamic and static simulation experiments were carried out for 4 weeks on 8Fr braided Ni-Ti alloy ureteral stent The components of calcified crystals on the surface of Ni-Ti alloy ureteral stent after 4 weeks were analyzed by energy dispersive spectrometer,scanning electron microscopy and Inductively coupled plasma atomic emission spectrometry,the encrustation degree of the scaffolds was evaluated by measuring the calcium and magnesium content of the scaffolds after dynamic and static simulation in vitro.The results showed that the degree of scaffold encrustation and the extent of encrustation increase in the static simulation of in vitro encrustation were greater than that in the dynamic simulation of in vitro encrustation,the accelerated dynamic simulation based on the in vitro calcification dynamic simulation device is closer to the clinical.(3)In vitro encrustation dynamic simulation device is used for the in vitro antiencrustation evaluation of a new type of coated stent tube.Ni-Ti alloy stents with different wall structures were fabricated and Chemical vapor deposition with parylene C coating.Firstly,the surface morphology of the stent was observed by scanning electron microscopy,and the static contact angle of the stent surface was measured by suspension method to characterize the infiltration,the number of adherent bacteria was measured by coating plate counting method.The surface contact angle increased to 125.97°,the hydrophobicity increased by 19.33% and the bacterial adhesion decreased by 45.41%.The results show that the coating treatment reduces the surface energy and dynamic friction coefficient of the stent,and makes it difficult for particles to adhere to the stent surface.Furthermore,the dynamic simulation device was used to simulate the preparation of the scaffolds for 2～4 weeks,and the content of calcium and magnesium ions on the scaffolds was determined,the results showed that the inhibition rates of Ca and Mg deposition on stent were 65.98% and 81.52% in 2 weeks group,61.69% and 71.03% in 4 weeks group,respectively.The results were in good correspondence with the results of antibacterial adhesion and surface hydrophobicity.The results show that the coating treatment can inhibit the encrustation deposition and has good antiencrustation stability.To sum up,this project designed and made a dynamic encrustation simulation device to reproduce the upper urinary tract environment in vitro,which improved the evaluation system of the encrustation performance of ureter stent in vitro.The antiencrustation performance of parylene C coated braided Ni-Ti alloy ureter stent was verified by simulation test in vitro.