Antimicrobial activities of silver used as a polymerization catalyst for a wound-healing matrix

Wound healing is a complex and orchestrated process that re-establishes the barrier and other functions of the skin. While wound healing proceeds apace in healthy individual, bacterial overgrowth and infection disrupts this process with significant morbidity and mortality. As such, any artificial matrix to promote wound healing must also control infecting microbes. We had earlier developed a two-part space-conforming gel backbone based on polyethyleneglycol (PEG) or lactose, which used ionic silver as the catalyst for gelation. As silver is widely used as an in vitro antimicrobial, use of silver as a catalyst for gelation provided the opportunity to assess its function as an anti-microbial agent in the gels. We found that these gels show bacteriostatic and bactericidal activity for a range of Gram-negative and Gram-positive organisms, including aerobic as well as anaerobic bacteria. This activity lasted for days, as silver leached out of the formed gels over a day in the manner of second-order decay. Importantly the gels did not limit either cell growth or viability, though cell migration was affected. Adding collagen I fragments to the gels corrected this effect on cell migration. We also found that the PEG gel did not interfere with hemostasis. These observations provide the basis for use of the gel backbones for incorporation of anesthetic agents and factors that promote wound repair. In conclusion, silver ions can serve dual functions of catalyzing gelation and providing anti-microbial properties to a biocompatible polymer.