Design of a simulated urethra model for the quantitative assessment of urinary catheter lubricity

Catheters designed for intermittent urological catheterization should possess appropriate lubricity and mechanical properties to ensure optimal clinical performance. However, the lack of a reproducible in vitro method that simulates clinical use makes it difficult to evaluate the lubricity of urinary catheters and other devices for urethral insertion. Therefore, this study describes a suitable method based on use of a Texture Analyzer to characterize the lubricity of such devices. The novel method was susequently applied to the evaluation of commercially-available intermittent urinary catheters. In addition, other important physicochemical properties of these catheters were examined, namely Young's modulus, degree of hydration and morphology. Catheter lubricity was quantified, using a Texture Analyzer, by measurement of the forces required for insertion and removal of the device from two model substrates, agar and mucin-coated silicone tubing. Significant differences in lubricity were identified between the commercially-available catheters, with Aquacath and Lofric exhibiting the lowest forces of insertion and removal. There were no significant differences between the extent of hydration between the catheters, with the exception of Uro-flo which exhibited the lowest hydration. Therefore, the differences in lubricity were not directly related to the extent of hydration. The forces required for insertion/removal of all catheters were markedly greater in the simulated mucin model than in the agar substrate and the former, simulated urethra model, was accepted to mimic more accurately, the in vivo situation. Significant differences were observed between the Young's Moduli of the catheter biomaterials, with Aquacath possessing the largest value. In conclusion, this study has described the use of a texture analyzer and polymeric substrates for the evaluation of biomaterial lubricity. Using these methods, Aquacath and Lofric catheters exhibited greatest lubricity. However, following additional consideration of the mechanical properties of these biomaterials, Aquacath possessed the most appropriate physicochemical properties for use in intermittent catheterization.