Abstract:

Objective This research aims to design a highly elastic knitted artificial bladder to overcome the limitations of current alien bladder implants, such as complex installation, more short-term complications, and demanding tissue engineering requirements. By employing spandex/polyethylene (PE) and spandex/polypropylene (PP) uniting with the polyurethane coating, the study seeks to enhance mechanical properties, durability, and pressure-controlled urination of the artificial bladder. The ultimate goal is to provide a more effective and reliable artificial bladder solution, thereby improving the quality of life of patients suffering from bladder resection.
Method The study used knitting techniques to create highly elastic fabrics from spandex/polyethylene covered yarn and spandex/polypropylene covered yarn. These fabrics were then sewn into bladder shapes and coated with a waterborne polyurethane membrane to produce the spandex/PE artificial bladder (FE), spandex/PP artificial bladder (FP), and pure polyurethane artificial bladder (FM). The mechanical properties, including tensile strength, burst resistance, and abrasion resistance, were evaluated to investigate the influence of the coating process on their mechanical properties. Microscopy and contact angle measurements were adopted to analyze the surface characteristics, so as to optimize the design of artificial bladder. Finally, the artificial bladders underwent compression urination tests to identify the optimal pressure-responsive urination functionality.
Results Under the microscope, spandex in the spandex/PE fabric exhibited a more compact loop structure compared to the spandex/PP fabric, with a smooth and flawless surface, making it more suitable to used as artificial bladders. Tensile tests showed that the knitted loop structure provided excellent elasticity to the artificial bladders. The FE achieved an elastic recovery rate of 92% at 100% elongation, outperforming both the FP and the FM. This high elasticity is because of the combined effect of the spandex core and polyurethane coating, which effectively disperses and absorbs stress during deformation. Burst tests further indicated a significant increase in the bursting strength of both FP and FE, with FE reaching a maximum of 74.71 N, an increase of 34.52% compared to the pre-coated fabric, demonstrating that the polyurethane coating significantly enhances the structural integrity. Rubbing tests showed that the coating process greatly improved the durability of the fabrics. The wear times of FP and FE increased by 6.15 and 6.27, respectively, compared to their pre-coated counterparts, confirming the protective role of the polyurethane layer. Surface analysis through contact angle measurements revealed that the coating process altered the fabric's surface properties, making the front side of the FE fabric hydrophilic (contact angle of 44.5°) and the back side hydrophobic (contact angle of 106.4°). This dual characteristic is crucial for preventing bacterial adhesion and maintaining urine flow. In compression urination tests, the FE bladder demonstrated superior performance, achieving the highest instantaneous flow under low pressure (125 mL/s under 3 N) and maintaining efficient urination control across varying pressures. The FP bladder performed best at high pressure, reaching the highest flow rate (289 mL/s under 9 N) but was less efficient under lower pressures. These findings suggest that the FE bladder offers a more balanced response across different pressure ranges, making it more suitable for practical applications.
Conclusion The highly elastic spandex/polyethylene and spandex/polypropylene artificial bladders were prepared by virtue of the elastic adjustable and flexible deformation of the looped structure of the knitted fabrics. The waterborne polyurethane coating process successfully improved the mechanical properties of the artificial bladder and validated the feasibility of the pressure urination strategy. In practical applications, the spandex/polyethylene artificial bladder shows stable and efficient compression urination performance under various pressures. This highly elastic artificial bladder with compression urination function can provide a possible alternative treatment for bladder resection.

Key words: artificial bladder, knit, membrana tectoria, coated elastic silk, high elasticity, medical textiles