Novel Coating Approaches for Polyethylene Biliary Stents to Reduce Microbial Adhesion, Prevent Biofilm Formation, and Prolong Stent Patency.

Background: Occlusion of plastic biliary stents is a common complication in biliary drainage, often requiring exchange procedures every 2-4 months due to microbial colonization and sludge formation. This study aimed to evaluate diamond-like carbon (DLC) coatings, with and without silver nanoparticle additives, for preventing stent occlusion. Methods: Polyethylene (PE) stents were coated with DLC using PlasmaImpax for DLC-1 and pulsed laser deposition for DLC-2. Silver ions (Ag) were incorporated into the DLC-2 coatings. To simulate in vivo conditions, a co-culture of Enterococcus faecalis (E. faecalis), Escherichia coli (E. coli), and Candida albicans (C. albicans) was used for microbial colonization. Standardized human bile simulated physiological conditions. Adhesion tests, weight measurements, and scanning electron microscopy (SEM) quantified bacterial adherence to stents. Results: DLC-1 coatings demonstrated higher bacterial growth than uncoated PE stents with E. faecalis (adhesion assay difference: 0.6 log [p = 0.19] and 0.1 log [p = 0.75] in rounds 1 and 2, respectively). In the bile incubation model, DLC-1 did not significantly reduce bacterial counts at 5 days (0.4 log [p = 0.06]) or 14 days (0.2 log [p = 0.44]). DLC-2 showed no significant reduction either. DLC-2-Ag significantly reduced bacterial adhesion (5 days: -0.3 log [p = 0.00]; 14 days: -0.4 log [p = 0.16]) and exhibited inhibition zones against E. faecalis (2.3 mm), E. coli (2.1 mm), and C. albicans (0.6 mm). SEM revealed cracks and flaking in the coating. Conclusions: DLC coatings alone did not prevent microbial adhesion. Tendencies of anti-adhesive properties were seen with Ag-doped DLC coatings, which were attributed to the antibacterial effects of Ag. Optimization of the DLC-coating process is needed to improve stent performance. Future studies with larger samples sizes are needed to confirm the observed trends.