Sustained release of usnic acid from graphene coatings ensures long term antibiofilm protection

Abstract

Protecting surfaces from bacterial colonization and biofilm development is an important challenge for the medical sector, particularly when it comes to biomedical devices and implants that spend longer periods in contact with the human body. A particularly difficult challenge is ensuring long-term protection, which is usually attempted by ensuring sustained release of antibacterial compounds loaded onto various coatings. Graphene have a considerable potential to reversibly interact water insoluble molecules, which makes them promising cargo systems for sustained release of such compounds. In this study, we developed graphene coatings that act as carriers capable of sustained release of usnic acid (UA), and hence enable long-term protection of surfaces against colonization by bacterial pathogens Staphylococcus aureus and Staphylococcus epidermidis. Our coatings exhibited several features that made them particularly effective for antibiofilm protection: (i) UA was successfully integrated with the graphene material, (ii) a steady release of UA was documented, (iii) steady UA release ensured strong inhibition of bacterial biofilm formation. Interestingly, even after the initial burst release of UA, the second phase of steady release was sufficient to block bacterial colonization. Based on these results, we propose that graphene coatings loaded with UA can serve as effective antibiofilm protection of biomedical surfaces.

Phytochemical Analysis, Antioxidant, Antimicrobial, and Cytotoxic Activity of Different Extracts of Xanthoparmelia stenophylla Lichen from Stara Planina, Serbia

“…In a study by Pompilio et al [48], the antibiofilm activity of usnic acid and atranorin, as pure substances, was examined, and it was shown that atranorin exhibited better action compared to usnic acid. A recent study showed that novel-type formulations such as usnic acid-impregnated graphene flakes could have a more prolonged antibiofilm activity [49]. In our study, XSH, the only extract that contained atranorin, showed the weakest antibiofilm effect compared to the other two tested extracts.…”

Graphene and its derivatives: “one stone, three birds” strategy for orthopedic implant-associated infections

“…Lyu et al 68 further constructed Dex-laden hierarchical ZnO nanotube/GO nanostructures via anodic oxidation, which brought osteogenicity and synergistic bactericidal activity to pure Zn implants. Pandit et al 69 developed usnic acid (UA)-graphene coatings, steadily releasing UA to enable long-term protection of implant surfaces against colonization by S. aureus and Staphylococcus epidermidis , even after the burst release of concentrations of UA. A team 70 synthesized polydopamine/GO- d -leucine ( d -leu) films which possessed pH-responsive antibacterial properties.…”

Graphene Properties, Synthesis and Applications: A Review

“…In another study, graphene coatings have been reported as a promising contender for anti-biofilm formation to prevent infection in medical implants. When the graphene layer is loaded with usnic acid (a strong antibacterial additive), the coating provides long-term anti-biofilm protection for up to 96 h. 167 The coating is highly effective against Staphylococcus aureus and S. epidermidis , two common biofilm-forming bacteria on medical implants.…”