Studies of degradable ureteric stents

A fully bioresorbable ureteric stent to clear occlusion, provide mechanical support for the ureter lumen during healing and as a post-operation prophylaxis is an ideal treatment for urinary obstructions. Metallic ureteric stents are available but problems due to bio-incompatibility and repeated cystoscopy are hindering their widespread usage. Meanwhile, investigations on biodegradable ureteric stent applications are insufficient to counteract the complications, in particular the failure of bioresorbable stents to degrade completely, encrustations and long-term usage. Durations of stent placements are also patient-dependent. Therefore, a sole biodegradable stent cannot fit the demands. The study investigates five types of bioresorbable polymeric stents, prepared by dip-coating, in a 16-week in vitro degradation study. The candidate polymers are poly-l-lactide-co-ε-caprolactone 70/30 (PLC), poly-l-lactide (PLLA), poly-l-lactide-co-glycolide (PLGA) 80/20 and two types of PLGA 50/50 intrinsic viscosities (IV) 1.01 and IV 0.16. The residual solvent, glass transition temperature and melting temperature are recorded. The in vitro degradation study investigates the water uptake, weight loss, molecular weights and effects of the porous tubes. PLGA 50/50 (IV 0.16) is not pursued for the in vitro degradation studies as it fragmented after vacuum-drying due to its low molecular weight. PLGA 50/50 IV 1.01 disintegrated after 21 days of immersion in PBS at 37ºC. PLGA 80/20 tubes were soft but remained intact after 84 days. PLC tubes cracked after 112 days while wrinkles were seen in PLLA structure. An interesting note is the tubular outer surfaces degraded faster than the inner surfaces. Further studies to optimize stent design, drug delivery and mechanical properties can be done.Bachelor of Engineering (Materials Engineering