A transcriptomic analysis of the bioactive properties of a polypropylene surgical mesh modified with silver-containing microparticles.

Permanent synthetic meshes are a prized option to promote soft-tissue support and repair in several surgical procedures. Contrariwise, the risk to develop biomaterial-associated infection (BAI) has not been solved. Intrinsically antibacterial materials, such as those that include metals with antimicrobial activity as part of their composition, are an advanced approach to be further explored for BAI prevention. In this study, a panel of in vitro, ex vivo and in vivo assays was used to compare a novel polypropylene-based surgical mesh modified with silver-containing microparticles with a commercially available similar device normally used for hernia repair. To comprehensively identify specific mechanisms of how the new silver-containing meshes influence the full host-tissue response in the presence and absence of infection, prostheses were screened for cytotoxicity, biological integration and transcriptomic responses, and additional antibiofilm production behaviour. Silver-modified polypropylene meshes exhibited good properties in terms of mechanical and cytotoxic values, as well as a modest prevention of biofilm formation. Moreover, they promoted connective tissue deposition and angiogenesis and, outstandingly, induced “immunomodulating” effects that may be potentially useful in the clinical context. Overall, the results substantiate the potential use of polypropylene surgical meshes modified with silver-containing microparticles as a means to prevent BAI in soft tissue repair. New silver-containing permanent polypropylene meshes were compared with a conventional lightweight polypropylene mesh commonly used in abdominal wall reconstructive surgery). Meshes (3 sq cm each) were placed onto the pre-fascia avascular plane and fixed in 7-wk-old male Sprague-Dawley Hairless rats (n=8 per mesh). Half of the implanted meshes (n=4) were directly inoculated with a suspension of Staphylococcus aureus-Xen 29 strain obtained from the exponential phase of growth (107 CFU). After 10 days, rats were euthanized and the engrafted prostheses together with the surrounding tissues were explanted by cutting around the area. Half of each implant was frozen for total RNA extraction. Once isolated, biological pools each containing 3 individual replicates of an equal quantity of RNA from each animal were constructed. Gene expression was analyzed in 3 different pools per condition using the Affymetrix Rat Gene 2.1 ST 16-Array Plate.