Practice Innovations
Chronic and acute dermal wounds can get infected, resulting in biofilm formation. Biofilms disrupt wound healing and are hard to eradicate (1). Thus, there is interest in developing wound dressings that can destroy biofilms with minimum cytotoxicity. We will present data on a dressing which has a 1) collagen matrix that promotes the transition of the wound to a remodeled, healed state; 2) embedded within this matrix are porous nanozeolite crystals with positively charged surfactant molecules 3) these nanozeolite crystals also encapsulate antimicrobial silver ions (2). We will present data comparing the zeolite-dressing with four of the leading silver-based commercial dressings in their ability to reduce bacterial load of mature Pseudomonas aeruginosa (PA01) biofilms using an invitro colony biofilm assay.
Methods: Wound dressings were prepared by deposition of silver-zinc ion-exchanged nanozeolites along with benzalkonium chloride on a commercially available ECM matrix. These dressings and the commercial dressings were introduced on top of a SWF (simulated wound fluid) layer on a 48-hour PA01 biofilm grown on a cellulose membrane resting on a nutrient-loaded agar gel. After well-defined periods of time (1-7 days), the bacteria on the dressing and the cellulose membrane were extracted and the bacterial colonies counted.
Results: The zeolite-encapsulated silver-based nanozeolite dressing performed significantly better (p< 0.05) than the commercial dressings in reducing the bacterial load of the biofilms. For days 1-4, there was no bacteria detected on the nanozeolite dressing or the cellulose membrane. The four commercial membranes all had residual bacteria on the dressing and the membrane.
Discussion: Silver will precipitate in wound fluids. The commercial dressings release silver into the SWF and are deactivated (3). By protecting the silver via encapsulation into the nanozeolite, we prevent its deactivation. We hypothesize that this advantage will translate to real infected wounds, thus requiring lower amounts of silver to maintain the antimicrobial efficacy as compared to commercial silver-dressings. We also hypothesize that lower amounts of silver will lead to lower cytotoxicity, and that the ECM dressing will promote wound healing. These hypotheses are currently being confirmed using an infected partial burn thickness porcine model.