Date of Award

5-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Bioengineering

Committee Member

Dr. Jiro Nagatomi, Committee Chair

Committee Member

Dr. O. Thompson Mefford

Committee Member

Dr. John Desjardins

Abstract

Approximately 92,000 ureteral stents are implanted every year to maintain urine flow after treatment of kidney stones, kidney transplants, and urinary incontinence. However, current ureteral stents have several downsides that include encrustation, urgency due to the proximal curl pressing on the bladder, patient pain from inflexible stents, and most importantly, the need for a follow up removal surgery. To address many of these current issues, a novel biodegradable stent was designed, fabricated, and characterized in the present studies. The innovative stent design features the use of biodegradable, FDA approved polydioxanone polymer material that was aimed to reduce encrustation and eliminate the need for a removal surgery. Additionally, the stent's novel coiled shape is intended to provide flexibility and anchor into the ureter. By eliminating the clinically conventional "double J" anchors, this could prevent the issue of the proximal anchor pressing on the bladder, remove the risk of encrustation on the distal anchor, and provide for better patient comfort by creating a more axially flexible stent. The novel stent was fabricated by winding a PDO suture around a mandrel and annealing at 100 °C. This annealing step increased the stiffness of the polymer as determined by cantilever bend testing. The source of this stiffness increase was determined to be due to an increase in crystallinity as verified by Differential Scanning Calorimetry and Wide Angle X-Ray Scattering. The results of custom testing in the present study also provided evidence that the stent exhibits adequate anchor strength and radial strength to maintain patency, which would allow standard ureteral flow conditions. Finally, an in vitro experiment demonstrated that the stent degrades in four weeks under normal physiological conditions, which is believed to be the ideal degradation time for the majority of ureteral stent applications. The results of this thesis provide strong supporting evidence that the proposed stent design has the ability to improve patient outcomes by addressing the drawbacks of current stent technology. However, further characterization efforts using animal models will be necessary to assure the safety and efficacy of this technology before it is ready for clinical use.

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