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

<b>Background</b>: 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. <b>Methods</b>: 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 <i>Enterococcus faecalis (E. faecalis)</i>, <i>Escherichia coli (E. coli),</i> and <i>Candida albicans (C. albicans)</i> 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. <b>Results</b>: DLC-1 coatings demonstrated higher bacterial growth than uncoated PE stents with <i>E. faecalis</i> (adhesion assay difference: 0.6 log [<i>p</i> = 0.19] and 0.1 log [<i>p</i> = 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 [<i>p</i> = 0.06]) or 14 days (0.2 log [<i>p</i> = 0.44]). DLC-2 showed no significant reduction either. DLC-2-Ag significantly reduced bacterial adhesion (5 days: -0.3 log [<i>p</i> = 0.00]; 14 days: -0.4 log [<i>p</i> = 0.16]) and exhibited inhibition zones against <i>E. faecalis</i> (2.3 mm), <i>E. coli</i> (2.1 mm), and <i>C. albicans</i> (0.6 mm). SEM revealed cracks and flaking in the coating. <b>Conclusions</b>: 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.