Wick effect: a comparative study of its potential for development using polypropylene and titanium mesh implant models

Background. Implant-associated infections are primarily driven by bacterial biofilm formation. While the physicochemical properties of the material surface are recognized as key factors in adhesion, the role of implant macromorphology, particularly its wicking effect that facilitates microbial spread, remains understudied. A comparative analysis of Staphylococcus aureus adhesion, a primary pathogen in such infections, on widely used polypropylene and titanium meshes in surgery is of significant interest for assessing long-term risks.

Objective. To conduct a comparative analysis of Staphylococcus aureus adhesion on titanium and polypropylene implants, focusing on the distribution pattern of microorganisms and assessing the potential biofilm formation risk associated with the wicking properties of the materials.

Materials and methods. This in vitro study used commercial mesh implants: polypropylene (Gynemesh PS, Johnson & Johnson, USA) and titanium (Titanium Silk, Elastic Titanium Implants LLC, Russia). Samples were incubated overnight with S. aureus VT209 at 37°C for 24 h. The number of adherent bacteria was quantitatively assessed using a culture-based method with colony-forming unit (CFU) counting. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to analyze the bacterial distribution and surface characteristics.

Results. The quantitative adhesion levels of S. aureus to titanium (Me=4.30×10² CFU [4.25×10²; 4.40×10²]) and polypropylene (Me=4.45×10² CFU [4.40×10²; 4.50×10²]) implants were comparable (p>0.05). However, a fundamental difference in the distribution patterns was observed. On titanium implants, adhesion was strictly localized to the edge areas with increased roughness and micro-defects, as confirmed by SEM and EDS. In contrast, the polypropylene implants showed a uniform distribution of bacteria over the entire surface, indicating the pronounced wicking properties of the material that facilitate passive spread and colonization of the entire available area.

Conclusion. Despite similar adhesion levels, the identified differences in microbial distribution indicate a higher potential risk of forming extensive biofilms that are difficult to eradicate with antibiotics and the immune system when using polypropylene implants owing to their pronounced wicking effect. Conversely, the localized nature of adhesion on titanium potentially simplifies the identification and surgical debridement of the infection focus. These findings challenge the safety of polypropylene from a long-term infectious risk perspective and highlight the critical need to develop implants with suppressed wicking properties or apply antimicrobial coatings over their entire surface.