The effective long-term use of indwelling ureteral
stents is often hindered by the formation of encrusting deposits which may cause obstruction and blockage of the
stent. Development of improved ureteral
stent biomaterials capable of preventing or reducing encrustation is therefore particularly desirable. In this study, the suitability as a ureteral
stent biomaterial of
Aquavene, a novel poly(
ethylene oxide)/
polyurethane composite
hydrogel was compared with that of
silicone and
polyurethane, two materials widely employed in ureteral
stent manufacture. Examination of
Aquavene in dry and hydrated states by confocal
laser 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 microm in diameter in the hydrated state.
Aquavene provided superior resistance to encrustation and intraluminal blockage over a 24-week period in a simulated urine flow model. Unobstructed urine flow continued with
Aquavene at 24 weeks, whereas
silicone and
polyurethane stents became blocked with encrustation at 8 and 10 weeks, respectively.
Weight loss within
Aquavene on the order of 9% (w/w) over the 24-week flow period indicates that extraction of the noncrosslinked poly(
ethylene oxide)
hydrogel may be responsible for the prevention of encrustation blockage of this
biomaterial. In the dry state,
Aquavene was significantly harder than either
silicone or
polyurethane, as shown by Young's modulus, and rapidly became soft on hydration. These additional properties of
Aquavene would facilitate ease of
stent insertion in the dry state past obstructions in the ureter and provide improved patient comfort on subsequent
biomaterial hydration in situ.
Aquavene is a promising candidate for use in the urinary tract, as it is probable that effective long-term urine drainage would be maintained in vivo. Further evaluation of this novel
biomaterial is therefore warranted.