Comparison of Ureteral Stent Biomaterials: Encrustation Profile in Lithogenic Artificial Urine Models

Ureteral stent encrustation significantly limits indwellingtimeand can lead to downstream urological problems. However, no idealpolymeric biomaterials have been shown to completely resist encrustationin long-term urine exposure. Recently, 2-hydroxyethyl methacrylate(HEMA)-coated Pellethane was reported as a promising biomaterial resistantto encrustation. This study compared HEMA-coated Pellethane to commerciallyavailable stents under two different artificial urine environments.To evaluate the degree and composition of encrustation on HEMA-coatedPellethane, Boston Scientific Tria, Bard InLay Optima, Cook UniversaHydrogel, and Cook Black Silicone stents were used at various dwellingtimes in two different artificial urine environments. In a batch-flowmodel, samples of stents were suspended in an artificial urine solution(AUS) at 37 & DEG;C. Every 24 h for 11 weeks, 50% of the AUS wouldbe replaced with fresh components using a programmable peristalticpump system. The stent materials were removed at suitable time intervalsand air-dried for 24 h under sterile conditions before follow-up analysis.SEM was used to assess the degree of encrustation, and inductivelycoupled plasma mass spectrometry (ICP-MS) was employed to quantifythe encrusted compositions, specifically for calcium, magnesium, andphosphorus. We measured the weight gain over time due to encrusteddeposits on the stents and quantified the amount of Ca, Mg, and Pdeposited on each encrusted stent. After the 11 week trial, HEMA-coatedPellethane showed the most average mass change. SEM showed that HEMA-coatedPellethane was fully encrusted in just 2 weeks in the AUS environments,and ICP-MS showed that Ca is the most abundant deposit. Among allthe tested stents, Black Silicone performed the best. The two AUSswere formulated to encrust more rapidly than physiological conditions.HEMA-coated Pellethane is not an ideal stent material, while siliconeis a promising material for advancing ureteral stents.