CHARACTERIZATION AND ASSESSMENT OF A NOVEL POLY(ETHYLENE OXIDE) POLYURETHANE COMPOSITE HYDROGEL (AQUAVENE(R)) AS A URETERAL STENT BIOMATERIAL/

The effective long-term use of indwelling ureteral stents is often hin dered by the formation of encrusting deposits which may cause obstruct ion and blockage of the stent. Development of improved ureteral stent biomaterials capable of preventing or reducing encrustation is therefo re particularly desirable. In this study, the suitability as a uretera l stent biomaterial of Aquavene(R), a novel poly(ethylene oxide)/polyu rethane composite hydrogel was compared with that of silicone and poly urethane, two materials widely employed in ureteral stent manufacture. Examination of Aquavene(R) in dry and hydrated states by confocal las er scanning microscopy, scanning electron microscopy, and atomic force microscopy showed the presence of numerous channels within a cellular matrix structure. The channel size increased considerably to as much as 10 mu m in diameter in the hydrated state. Aquavene(R) provided sup erior resistance to encrustation and intraluminal blockage over a 24-w eek period in a simulated urine flow model. Unobstructed urine flow co ntinued with Aquavene(R) at 24 weeks, whereas silicone and polyurethan e stents became blocked with encrustation at 8 and 10 weeks, respectiv ely. Weight loss within Aquavene(R) on the order of 9% (w/w) over the 24-week flow period indicates that extraction of the noncrosslinked po ly(ethylene oxide) hydrogel may be responsible for the prevention of e ncrustation blockage of this biomaterial. In the dry state, Aquavene(R ) was significantly harder than either silicone or polyurethane, as sh own by Young's modulus, and rapidly became soft on hydration. These ad ditional properties of Aquavene(R) would facilitate ease of stent inse rtion in the dry state past obstructions in the ureter and provide imp roved patient comfort on subsequent biomaterial hydration in situ. Aqu avene(R) is a promising candidate for use in the urinary tract, as it is probable that effective longterm urine drainage would be maintained in vivo. Further evaluation of this novel biomaterial is therefore wa rranted. (C) 1995 John Wiley & Sons, Inc.