Improving resistance to biliary stent occlusion by surface hydrophilization and amidation through plasma treatment to the inner surface of polyethylene tubes.

Biliary stents are medical devices inserted into the bile duct to treat biliary strictures. However, inserted stents can become occluded within a few months after placement. In this study, the inner surface of a polyethylene (PE) tube was plasma-treated with helium (He), nitrogen (N2), oxygen (O2), and their gas mixtures to improve resistance to stent occlusion. Surface characteristics were analyzed by water contact angle (WCA) and x-ray photoelectron spectroscopy (XPS) measurements. In the WCA results, bare PE without plasma treatment was the most hydrophobic at 100.7°, whereas PE(He) plasma-treated with He gas became the most hydrophilic at 26.1°. XPS deconvolution analysis revealed that the PE(He) and PE(He/N2) contained a considerable proportion of O 1s present as amide (-CONH-) groups exceeding 40%, whereas the other samples had proportions below 7%. The resistance to stent occlusion was verified through microbial and cancer cell adhesion assays. In the microbial adhesion assay, Escherichia coli (E. coli) was used, and PE(He) showed a statistically significant reduction in E. coli growth compared to bare PE. Inhibition of cancer cell adhesion was the most pronounced in PE(He) and PE(He/N2), with reductions in fluorescence intensities of 75.5% and 81.5%, respectively. Overall, both surface hydrophilization and amidation were found to be effective in inhibiting the adhesion of organic contaminants. It was proposed that plasma surface treatment has the potential to improve resistance to biliary stent occlusion.