Professor Pennsylvania State University, United States
Introduction: : Electrical nerve block delivers localized stimulation to peripheral nerves to reversibly suppress pain without drugs. Unlike opioids or anesthetics, it enables targeted, on-demand modulation with reduced systemic risks. However, commercial devices often use non-degradable materials like polyurethane, causing fibrosis, inflammation, and nerve compression. Their stiffness (Young’s modulus ~10–100 MPa) contrasts sharply with soft nerve tissue (~10–100 kPa), increasing injury risk and necessitating surgical removal. To address this, biodegradable nerve block catheters made from citrate-based elastomers have emerged. These materials offer high elasticity, tunable degradation, and safe resorption. These catheters naturally degrade after use, removing the need for extraction while maintaining efficacy in preclinical pain models. Overall, biodegradable nerve block devices offer a safer, mechanically compatible, and fully resorbable platform for temporary neuromodulation therapies.
Materials and
Methods: : The citrate-based prepolymer CXBE was synthesized via cost-effective, catalyst-free polycondensation of citric acid, 1,8-octanediol, and xylitol. After precipitation in DI water and lyophilization, the prepolymer was reacted with hexamethylene diisocyanate (HDI, 1.5:1 molar ratio) at 60 °C for 14 days to form CXBE urethane-doped polyester (CXBE-UPE), enhancing elasticity and molecular weight. For catheter fabrication, solvent evaporation at room temperature yielded a flexible sheet, which was rolled and thermally crosslinked at 80 °C and 120 °C over three days. Mechanical properties under dry and wet conditions were assessed using an Instron to evaluate flexibility and softness. Degradation and swelling studies confirmed biodegradability over several weeks. The antibiotic properties were confirmed by cultivating Staphylococcus aureus (S. au) with CXBE-UPE and optical density was read by plate reader. DPPH, ion chelation, and ABTS assays were performed to confirm the antioxidant properties of our innovative catheter. Biocompatibility was verified using L929 cells exposed to catheter leachates.
Results, Conclusions, and Discussions:: CXBE, a citrate-based elastomer, exhibits exceptional swelling behavior—exceeding 200%—and tunable degradation rates ranging from under one week to over six months, depending on formulation parameters. However, despite its biodegradability and hydrophilic nature, the addition of xylitol, a tri-functional crosslinking agent, imparts brittleness to the polymer matrix, rendering CXBE unsuitable for applications requiring high flexibility, such as catheterization. To overcome this limitation and better mimic the mechanical performance of commercial catheters, hexamethylene diisocyanate (HDI) was introduced as a crosslinking reagent to form urethane linkages. This modification led to the development of CXBE-UPE, a urethane-crosslinked prepolymer with significantly improved elasticity and mechanical strength. To facilitate real-time tracking and localization of the implant post-surgery, a fluorescent moiety was incorporated into the CXBE network. The resulting fluorescent CXBE materials exhibited strong emission across a broad spectral range (250–700 nm), enabling non-invasive, in-situ monitoring of both degradation and positioning within biological tissues. In vitro studies demonstrated that CXBE-UPE retains biodegradability, with approximately 50% mass loss observed and maintain functional mechanical properties by week 10 under physiological conditions. Furthermore, the material exhibited antibacterial activity against Staphylococcus aureus, likely due to the release of degradation products. Antioxidant properties were validated through three independent assays, showing superior radical scavenging capability compared to commercial catheter materials. Importantly, biocompatibility assessments using L929 fibroblast cells revealed nearly 100% viability when cultured with leachates from the CXBE-UPE catheter, confirming its safety for in vivo application. Building on these promising results, the study plans to evaluate the catheter in porcine models to confirm its functionality, degradation profile, and biocompatibility in a large animal system, advancing the potential clinical translation of this biodegradable and trackable neural catheter.
