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Antibacterial Efficacy of Silver-Impregnated Polyelectrolyte Multilayers Immobilized on a Biological Dressing in a Murine Wound Infection Model

Guthrie, Kathleen M. DVM; Agarwal, Ankit PhD; Tackes, Dana S. BS; Johnson, Kevin W. BS; Abbott, Nicholas L. PhD; Murphy, Christopher J. DVM, PhD; Czuprynski, Charles J. PhD; Kierski, Patricia R. BA, CVT; Schurr, Michael J. MD; McAnulty, Jonathan F. DVM, PhD

doi: 10.1097/SLA.0b013e318256ff99
Original Articles

Objective: To investigate the antibacterial effect of augmenting a biological dressing with polymer films containing silver nanoparticles.

Background: Biological dressings, such as Biobrane, are commonly used for treating partial-thickness wounds and burn injuries. Biological dressings have several advantages over traditional wound dressings. However, as many as 19% of wounds treated with Biobrane become infected, and, once infected, the Biobrane must be removed and a traditional dressing approach should be employed. Silver is a commonly used antimicrobial in wound care products, but current technology uses cytotoxic concentrations of silver in these dressings. We have developed a novel and facile technology that allows immobilization of bioactive molecules on the surfaces of soft materials, demonstrated here by augmentation of Biobrane with nanoparticulate silver. Surfaces modified with nanometer-thick polyelectrolyte multilayers (PEMs) impregnated with silver nanoparticles have been shown previously to result in in vitro antibacterial activity against Staphylococcus epidermidis at loadings of silver that are noncytotoxic.

Methods: We demonstrated that silver-impregnated PEMs can be nondestructively immobilized onto the surface of Biobrane (Biobrane-Ag) and determined the in vitro antibacterial activity of Biobrane-Ag with Staphylococcus aureus. In this study, we used an in vivo wound infection model in mice induced by topical inoculation of S aureus onto full-thickness 6-mm diameter wounds. After 72 hours, bacterial quantification was performed.

Results: Wounds treated with Biobrane-Ag had significantly (P < 0.001) fewer colony-forming units than wounds treated with unmodified Biobrane (more than 4 log10 difference).

Conclusions: The results of our study indicate that immobilizing silver-impregnated PEMs on the wound-contact surface of Biobrane significantly reduces bacterial bioburden in full-thickness murine skin wounds. Further research will investigate whether this construct can be considered for human use.

A new method of augmenting biological dressings with silver has been developed that allows very low concentrations of silver to be immobilized in the dressing. The antibacterial efficacy of this new technology is tested in an in vivo full-thickness murine model. Wounds are inoculated and covered with an untreated dressing, or a dressing augmented with silver.

*School of Veterinary Medicine, Department of Surgical Sciences

Department of Chemical and Biological Engineering

School of Veterinary Medicine, Department of Pathobiological Sciences

§School of Medicine, Department of Surgery, University of Wisconsin

School of Medicine, Department of Ophthalmology and Vision Science and School of Veterinary Medicine, Department of Surgical and Radiological Sciences, University of California, Davis.

Reprint: Jonathan McAnulty, DVM, PhD, Department of Surgical Sciences, University of Wisconsin, School of Veterinary Medicine, 2015 Linden Drive, Madison, WI 53706, E-mail: mcanultj@svm.vetmed.wisc.edu; and Michael Schurr, MD, University of Wisconsin, School of Medicine, Department of Surgery, G5/331 Clinical Science Center, 600 Highland Avenue, Madison, WI 53792. E-mail: schurr@surgery.wisc.edu.

Disclosure: Funding for all experiments was provided by the National Institutes of Health (RC-2 grant). A.A., N.L.A., C.J.M., C.J.C., M.J.S., and J.F.M. are founding members of Imbed Biosciences, Inc.

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