The in vitro degradation of a novel gradient-degradable ureteral stent based on copolymers of TMC and GA

Ke Hu^1,2Yu Zhang¹Xinmiao Ma¹Shouhua Han²Tianyang Zhou³Xiancheng Li^1*Zhipeng Hou^2*

• ¹Department of Urology, Second Affiliated Hospital of Dalian Medical University, Dalian, China
• ²Research Center for Biomedical Materials, Shengjing Hospital of China Medical University, Shenyang China, China
• ³Division of Hepatobiliary and Pancreatic Surgery, Department of General Surgery, The Second Hospital of Dalian Medical University, Dalian, Liaoning, 116023, China, Dalian, Liaoning, China

Ureteral stent placement is a commonly executed clinical intervention for the treatment of upper urinary tract diseases. However, conventional non-degradable stents necessitate secondary extraction and are associated with complications such as infections, stone formation, and irritative symptoms when left indwelling for extended durations. To mitigate these risks, we introduce a novel three-layer gradient degradable ureteral stent (PTGGDG) developed from copolymers of TMC and GA [P(TMC-co-GA), abbreviated as PTG] using a multilayer impregnation technique. The structural design comprises PTG6040, PTG5050, and PTG4060 layers arranged from the inner layer to the outer layer. The present study systematically explored the relationship between the molecular chemical structure of the stent and its macroscale performance under varying proportions. The findings of this study demonstrate that PTGGDG exhibits a tensile strength of 34.69 MPa, coupled with exceptional flexibility, thus substantiating its compliance with the stringent mechanical support criteria stipulated for ureteral stents. The degradation behavior of PTG ureteral stents was rigorously assessed in artificial urine (AU) and aspergillus oryzae lipase-PBS (AP) environments. By modulating the PGA content in the formulation, the stents exhibited controllable degradation rates and maintained satisfactory morphological stability. In the present study, the stent was found to undergo predominantly hydrolytic degradation driven by GA, with the gradient structure extending functional support and minimising abrupt structural failure over a degradation period of 42 days. The PTGGDG stent undergoes preferential degradation of the outer layer in the AU due to the rapid degradation of its PTG4060 component. The middle layer's PTG5050 plays a buffering role in this process. The inner layer's PTG6040 degrades more slowly, ensuring a smooth lumen flow and allowing the degradation fragments to be discharged with artificial urine. This prevents obstruction of the ureteral stent fragments.In AP, the predominant form of erosion was enzymatic, driven by TMC, resulting in a degradation timeframe of 13 days. This gradient design is promising as it maintains urinary luminal patency while facilitating degradation in accordance with clinical requirements, thereby keeping urine pH within physiological ranges and providing insights for the optimization of materials and structural integrity in degradable ureteral stents.