Aerogel hollow tubes from natural-origin polysaccharides as tailor-made urinary stents

A urinary stent is defined as a thin tube which is inserted in the ureter to prevent or treat the obstruction of urine flow from the kidney. Silicone, latex, polyvinylchloride and polyurethanes are the most widely used materials for the preparation of the stents. Nonetheless, major drawbacks still concern urologists regarding their application. Severe clinical complications may result from the use of these materials such as fracture, encrustation and infection. Particularly serious are bacterial infections which represent the cause of several morbidity and mortality cases. Furthermore, the use of these materials requires the need for a second surgery to remove the stent.

In this work, the possibility to prepare aerogel hollow tubes from natural origin polysaccharides, in particular alginate, k-carragenaan, gellan gum and a blend of these with gelatin was evaluated. The hollow tubes were prepared following the conventional aerogel processing steps and were characterized by different techniques. Scanning electron microscopy (SEM) was used to evaluate their surface morphology. Water uptake and degradation were followed by weigh measurements at predetermined timeframes in simulated urine solution. SEM and FTIR was used to evaluate the encrustation (the deposition of calcium salts that may obstruct the stent) of the developed stents. The mechanical properties of the prepared materials were evaluated in tensile mode. In vitro performance demonstrates that the degradation of the materials in solution can be tuned between 14 and 60 days, preventing therefore the need for a second surgery. Additionally, no encrustation was observed for the tested time periods (up to 60 days).

We demonstrated that it is possible to use natural origin, biodegradable polymers (with inherent anti-bacterial properties) to prepare urinary stents with adequate morphology and mechanical properties. The developed devices do not present encrustation, avoiding the need for a second surgery. All the reported characteristics are foreseen as major breakthroughs in the development of biocompatible and biodegradable urinary stents.