Development of a 3D-Printed Biodegradable Polymeric Ureteral Stent

Development of a 3D-Printed Biodegradable Polymeric Ureteral Stent

Aaliya Nausheen¹, Drishya Bhandary¹, Kumkum Bharadwaj¹, Nehasri SH¹, Mr K Ram Kumar² ¹ U.G. Student, Biomedical Engineering, ACS College of Engineering, Bangalore, India

² Department of Biomedical Engineering, ACS College of Engineering, Bangalore, India

i

Abstract Traditional ureteral stents, commonly made from non- biodegradable polymers or metals, are associated with several complications such as infection, encrustation, migration, and the necessity for secondary surgical removal. To overcome these limitations, this project focuses on the development of a biodegradable polymeric ureteral stent that can degrade safely within the urinary tract after fulfilling its function.

The primary objective was to design and fabricate a stent that provides temporary internal support for urinary drainage while minimizing patient discomfort and eliminating the need for retrieval procedures. Polylactic Acid (PLA) was selected as the base material due to its biocompatibility and degradability, reinforced with magnesium and zinc nanoparticles to enhance mechanical strength and control the degradation rate. Chitosan and hyaluronic acid coatings were applied to impart antimicrobial and anti-inflammatory properties.

The stent was modeled using Fusion 360, structurally analyzed through Finite Element Analysis (FEA) in ANSYS, and fabricated via 3D printing. Surface coatings were applied post-fabrication using a controlled dipping method.

Simulation and fabrication results confirmed the structural viability, dimensional accuracy, and effective surface coating of the stent. The proposed design presents a promising biodegradable alternative to conventional stents, potentially improving patient outcomes and reducing healthcare costs.

KeywordsBiodegradable stent, ureteral stent, Polylactic Acid (PLA), magnesium nanoparticles, zinc nanoparticles, chitosan coating, hyaluronic acid, finite element analysis (FEA), 3D printing, biomedical device.

1. INTRODUCTION

   Ureteral stents play a vital role in urological interventions by ensuring the continuous drainage of urine from the kidneys to the bladder in cases of obstruction, post-operative healing, or surgical intervention. Traditional stents, typically fabricated from non-biodegradable polymers such as polyurethane and silicone, or metals like stainless steel, pose several clinical challenges. These include stent encrustation, urinary tract infections (UTIs), migration, patient discomfort, and the need for a secondary surgical procedure for stent removal.

   Forgotten or retained stents may further result in serious complications, including obstructive uropathy or renal impairment.

   Biodegradable stents present a promising alternative to conventional options by eliminating the need for surgical retrieval and reducing long-term complications. These stents are designed to maintain ureteral patency for a defined duration and subsequently degrade safely within the body. Polylactic Acid (PLA), a bioresorbable polymer widely accepted in biomedical applications, offers biocompatibility, hydrolytic degradability, and compatibility with additive manufacturing techniques.

   To address the mechanical and biological limitations of PLA, reinforcement with magnesium (Mg) and zinc (Zn) nanoparticles was introduced. These nanoparticles improve tensile strength, modulate the degradation profile, and offer antimicrobial properties. In addition, the stent was coated with chitosan to inhibit bacterial colonization and hyaluronic acid to reduce inflammation and enhance tissue interaction.

   This paper presents the design, simulation, fabrication, and surface treatment of a biodegradable PLA-based ureteral stent using advanced tools such as Fusion 360 for CAD modeling, ANSYS for Finite Element Analysis (FEA), and 3D printing for prototype development. The goal is to provide a patient- specific, biocompatible, and mechanically robust solution that addresses the limitations of current ureteral stent technologies.

2. RELATED WORK

   Conventional ureteral stents, while essential for maintaining urinary drainage, are frequently associated with complications such as encrustation, infection, migration, and the need for secondary surgical removal. Mosayyebi et al. [1] highlighted that complication rates can approach 100% in clinical practice, emphasizing the urgent need for a safer, patient-friendly alternative. These limitations have fueled interest in biodegradable materials that degrade in situ and eliminate the need for follow-up procedures.

   Polylactic Acid (PLA) is among the most widely studied biodegradable polymers for biomedical applications. Sousa et al. [4] demonstrated that 3D-printed PLA stents exhibit favorable mechanical strength and support cellular growth, validating its use in temporary implants. Early clinical studies by Tammela and Talja [7], as well as Azuma and Chancellor [8], confirmed that PLA-based stents function effectively and naturally resorb in vivo, minimizing long-term risks.

   To overcome PLAs mechanical and antimicrobial limitations, nanoparticle reinforcement has been explored. Lock et al. [5] reported that magnesium not only enhances mechanical durability but also provides intrinsic antibacterial activity. Similarly, Durán et al. [3] observed that zinc-containing composites and chitosan coatings improve compatibility with human immune cells, reducing infection risks and supporting healing.

   Surface modifications further improve stent performance. Chitosan, a biocompatible and antimicrobial biopolymer, was found to enhance tissue integration and suppress bacterial colonization [3]. Hyaluronic acid has also been employed as a coating to reduce inflammation and improve epithelial response, making it an ideal adjunct in urinary implants.

   Stent geometry plays a critical role in device efficacy. Siggers et al. [6] showed through finite element analysis (FEA) that improper stent shapes can cause urine stagnation and encrustation. Amnieh et al. [9] demonstrated that geometrical optimization of PLA stents reduces stress concentrations and improves degradation uniformity. These insights informed the CAD and FEA-driven design approach used in this project.

   Together, these studies support the rationale for a biodegradable ureteral stent composed of PLA reinforced with Mg/Zn nanoparticles and coated with chitosan and hyaluronic acid engineered using 3D printing and simulation tools to achieve functional and clinical relevance.

3. METHODOLOGY

   1. Materials

      The primary material utilized for stent fabrication was medical- grade Polylactic Acid (PLA), selected for its biodegradability, biocompatibility, and compatibility with additive manufacturing. PLA was procured in the form of 1.75 mm filament from certified biomedical polymer suppliers (e.g., NatureWorks, Evonik), with a molecular weight of 150,000 200,000 g/mol. The material exhibits a glass transition temperature of 5560°C and a melting point of 170180°C, making it suitable for Fused Deposition Modeling (FDM).

      To improve mechanical properties and impart antibacterial functionality, the PLA matrix was reinforced with magnesium (Mg) and zinc (Zn) alloy nanoparticles. Magnesium nanoparticles, with an average particle size of 50100 nm, enhance tensile strength and release antibacterial ions during degradation. Zinc alloy nanoparticles, ranging from 3080 nm in size and composed primarily of Zn with trace Mg and Ca, moderate the degradation rate hile contributing to antimicrobial action. Nanoparticles were sourced from vendors such as Sigma-Aldrich and NanoResearch Elements.

      For surface functionalization, chitosan and hyaluronic acid (HA) were employed. Chitosan powder with a molecular weight of 190,000310,000 Da and a degree of deacetylation

      80% was used for its antimicrobial and anti-inflammatory properties. Pharmaceutical-grade HA (molecular weight

      >1,000,000 Da) was used to enhance epithelial compatibility and reduce inflammatory responses.

      Fig. 1 illustrates the step-by-step process of developing a biodegradable ureteral stent using PLA reinforced with Mg/Zn nanoparticles, including material selection, design, simulation, fabrication, post-processing, and evaluation.

   2. Stent Design

      Computer-Aided Design (CAD) modeling was performed using Autodesk Fusion 360, which allowed parametric control of geometry. The stent was modeled as a cylindrical, mesh- patterned structure to provide flexibility, radial strength, and uniform degradation. The final design parameters were as follows: 25 cm in length, 0.3 cm inner diameter, 0.356 cm outer diameter, and a mesh density of 8260 triangular elements, resulting in a high-resolution model suitable for simulation and fabrication. The aspect ratio of 17.5 ensured anatomical compatibility and resistance to kinking.

   3. Simulation and Analysis

      Structural simulations were conducted using ANSYS Workbench, employing Finite Element Analysis (FEA) to validate the stents mechanical performance under physiological conditions. The PLAMg/Zn composite was

      modeled as an isotropic biodegradable thermoplastic using estimated material properties from the literature.

      Simulation parameters included:

      • Boundary conditions: One end fixed to simulate renal anchoring.

      • Loading: Uniform radial pressure between 1020 mmHg to replicate peristalsis.

      • Meshing: Fine tetrahedral elements for accurate stress distribution.

      • Analyses: Static structural analysis for stress/deformation and fatigue analysis for cyclic loading.

        Simulation results guided iterative design refinement and confirmed that the stent structure could withstand physiological pressures without collapse or fracture.

   4. Fabrication Process

      The optimized CAD model was fabricated using a high-resolution desktop FDM 3D printer, capable of

      processing composite PLA filaments. Printing was performed with the following parameters:

      • Layer height: 0.1 mm

      • Infill density: 90%

      • Extruder temperature: 200210°C

      • Bed temperature: 60°C

      • Printing speed: 40 mm/s

      • Cooling: Active fan-based solidification

        The mesh geometry was printed in a vertical cylindrical orientation to maintain uniform mechanical integrity and dimensional accuracy. Post-processing steps included cleaning with 70% isopropyl alcohol, rinsing with distilled water, and UV sterilization for 1520 minutes prior to coating.

   5. Coating Procedure

   A chitosan solution was prepared by dissolving 0.15 g of chitosan in a mixture of 0.1 mL 100% lactic acid and 9.9 mL distilled water. The solution was stirred and gently heated until clear. The stents were immersed in the solution and uniformly coated using a sterile soft brush. After coating, the stents were air-dried at ambient conditions for 45 hours.

   An optional secondary coating of hyaluronic acid was applied either as a top layer or co-dissolved with chitosan to enhance mucosal compatibility. Coating uniformity was assessed through visual inspection and weight measurement before and after application. The final coating adhered uniformly, forming a bioactive layer to support antimicrobial action and controlled degradation.

4. RESULTS

   1. CAD Modeling

      The ureteral stent was successfully designed in Autodesk Fusion 360 with precise control over dimensions and geometry. The final model consisted of a cylindrical mesh structure with hexagonal lattice units, optimized to balance

      flexibility and radial strength. Design specifications included a length of 25 cm, an inner diameter of 0.3 cm, and an outer diameter of 0.356 cm. A high-resolution mesh comprising 8260 triangular elements ensured manufacturability and simulation accuracy.

      Fig. 2 presents the rendered CAD model, demonstrating the uniformity of the mesh structure and the stents elongated profile suitable for ureteral insertion.

   2. Finite Element Analysis (FEA) Simulation

   FEA simulations were performed using ANSYS Workbench to validate the stents structural performance under physiological loading conditions. A static structural analysis was conducted using a radial inward pressure of 1020 mmHg to simulate peristaltic compression. The material model included a PLA matrix reinforced with Mg/Zn nanoparticles, approximated as an isotropic biodegradable thermoplastic.

   Fig. 3 Finite element mesh design of the stent structure generated using FEA simulation.

   Fig. 4. Distribution of von Mises stress and displacement along the length of the stent. The stress peaks at approximately

   7.84 MPa, remaining below the material's yield strength, while the maximum displacement reaches 0.48 mm, indicating no structural failure.

   The CAD design was fabricated using a high-resolution FDM 3D printer with Mg/Zn-infused PLA filament. The mesh structure was successfully printed in a cylindrical orientation with no visible defects. Layer bonding was consistent, and the printed dimensions closely matched the CAD specifications (within ±0.01 cm tolerance). The mesh openings were well- defined, allowing post-processing steps such as coating and drying to be effectively applied.

   Fig. 5 shows the 3D-printed prototype after fabrication, displaying structural integrity and clarity of the mesh geometry.

   D. Coating Characterization

   The coating procedure resulted in a uniform chitosan layer across the entire surface of the stent. Visual inspection confirmed complete coverage, particularly in mesh joints and

   curvature zones. The coating adhered firmly to the PLA substrate without flaking or peeling after drying. A secondary layer of hyaluronic acid was optionally applied in selected samples, which also demonstrated smooth coverage.

   Fig. 6 displays the final coated stent, showing smooth surface finish and coloration typical of chitosan-treated PLA.

   Weight measurements before and after coating showed an average increase of 0.012 g per stent, indicating consistent application across all samples.

5. DISCUSSION

   The development and evaluation of the biodegradable polymeric ureteral stent in this study offer a compelling solution to long-standing issues associated with conventional stents, including infection risk, encrustation, patient discomfort, and the need for surgical removal. By integrating biodegradable materials, nanoparticle reinforcement, and bioactive coatings, this design aligns with current biomedical innovation trends aimed at reducing patient morbidity and healthcare costs.

   1. Addressing Conventional Stent Limitations

      Traditional stents, typically composed of polyurthane or silicone, require a secondary invasive procedure for removal and are prone to complications such as encrustation and biofilm formation [1]. The proposed stent, fabricated from PLA reinforced with magnesium and zinc nanoparticles, is designed to degrade safely in situ after fulfilling its clinical function. This eliminates the need for retrieval and reduces associated procedural risks and costs.

      The mesh-patterned geometry, optimized through CAD and validated via FEA, enhances flexibility and radial strength

      while maintaining patency under peristaltic motion. These features ensure that the stent adapts to the dynamic ureteral environment without causing obstruction or trauma challenges frequently encountered in non- biodegradable stents.

   2. Role of PLA and Nanoparticles

      Polylactic Acid (PLA) was selected as the base polymer due to its established use in resorbable medical devices and its favorable degradation profile [4], [7]. However, PLA alone has limitations in mechanical performance and antibacterial activity. Reinforcing PLA with magnesium and zinc alloy nanoparticles significantly enhanced mechanical integrity and introduced antimicrobial properties, as supported by Lock et al.

      [5] and Durán et al. [3].

      Magnesium ions are known to disrupt bacterial cell walls, and zinc contributes to both structural stability and immune modulation. The composite material was shown through FEA simulation to withstand physiological pressure ranges (1020 mmHg), with a safety factor greater than 1.5, confirming its mechanical viability.

   3. Effectiveness of Coatings

      Surface functionalization using chitosan and hyaluronic acid coatings played a critical role in improving biocompatibility. Chitosan, a naturally derived polymer, has been demonstrated to inhibit bacterial adhesion and support healing [3], while hyaluronic acid serves as an anti-inflammatory agent that minimizes urothelial irritation and fibrosis.

      Visual and tactile inspection of coated prototypes revealed a uniform bioactive film with excellent adhesion, suggesting effective surface interaction. These findings are consistent with literature reports advocating multilayered biopolymer coatings for urinary implants [3], [8].

   4. Comparison with Existing Literature

      Compared to prior studies, this project integrated multiple validated approaches into a single, cohesive design. While Sousa et al. [4] and Amnieh et al. [9] focused on PLA-based and geometrically optimized stents respectively, this study combined those design principles with nanocomposite reinforcement and biologically active coatingsan approach not fully realized in prior experimental prototypes.

      Furthermore, unlike early-generation biodegradable stents which often lacked sufficient mechanical durability [7], this stent design addresses the dual need for strength during the implantation period and complete resorption thereafter.

   5. Limitations and Future Work

      While the initial results are promising, this study has several limitations. Notably, all evaluations were conducted in vitro,

      and biological interactions such as inflammatory response, degradation kinetics in urine, and long-term biofilm resistance remain untested. Additionally, the coating characterization was limited to visual and gravimetric methods due to lack of access to advanced instrumentation like SEM or FTIR.

      Future research will focus on:

      • Conducting cytotoxicity and biocompatibility assays with urothelial cell lines;

      • Developing in vitro urine flow models to evaluate degradation and encrustation;

      • Implementing in vivo animal testing to assess stent performance in biological environments;

      • Exploring drug-eluting coatings for site-specific therapeutic delivery.

   Ultimately, clinical translation would require large-scale prototyping, regulatory validation, and cost-benefit analysis compared to current clinical stenting options.

6. CONCLUSION

This study presents the design, simulation, fabrication, and preliminary evaluation of a biodegradable polymeric ureteral stent aimed at overcoming the limitations of conventional non- degradable stents. The stent was developed using medical- grade Polylactic Acid (PLA), reinforced with magnesium and zinc alloy nanoparticles to enhance mechanical strength and antimicrobial performance. The use of a mesh-based geometry, designed in Fusion 360 and validated through Finite Element Analysis (FEA) in ANSYS, demonstrated sufficient structural integrity under physiological conditions.

Fabrication using Fused Deposition Modeling (FDM) achieved high dimensional accuracy and structural consistency. The application of chitosan and hyaluronic acid coatings further improved surface biocompatibility, suggesting the potential for reduced encrustation, inflammation, and bacterial colonization.

Compared to prior research, the current approach integrates multiple advancesincluding biodegradable materials, mechanical reinforcement, and functional coatingsinto a single stent prototype. While initial results support the feasibility of this design, further biological validation, including in vitro cytotoxicity testing and in vivo animal trials, is essential before clinical application.

The study lays a strong foundation for the future development of customizable, resorbable ureteral stents that reduce the need for retrieval procedures, improve patient comfort, and lower healthcare costs

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