Novel Silver Dressing Preserves Reparative Cells in Wounds

An experimental approach to wound healing takes advantage of silver's antibacterial properties, sidestepping the damage it can cause to the cells needed for healing.

A researcher at the University of Wisconsin (Madison, USA) embedded silver nanoparticles within polyelectrolyte multilayers (PEMs), with 6.45 cm2 of the PEM material containing just 0.4% of the amount of silver that is usually found in the silver-treated antibacterial bandages currently used. In laboratory tests, the low concentration of silver killed 99.9999% of the bacteria, but did not damage the fibroblast cells that are required to repair a wound. PEMs are constructed using a layer-by-layer deposition technique. During deposition, a suitable growth substrate (usually charged) is dipped back and forth between dilute baths of positively and negatively charged polyelectrolyte solutions. During each dip, a small amount of polyelectrolyte is adsorbed and the surface charge is reversed, allowing the gradual and controlled build-up of electrostatically cross-linked films of polycation-polyanion layers. A precise dose of silver is then added, since the system is so sensitive that increasing the silver dose from 0.4% to just 1% of the level commonly used in a commercial dressing severely damaged the fibroblasts. The study was presented at the American Chemical Society's national meeting and Exposition, held during August 2009 in Washington DC, (USA).

"This study goes beyond prior reports by characterizing the interactions of silver-impregnated polyelectrolyte multilayers with mammalian cells, and by identifying the minimum silver loading required for antibacterial activity,” said study presenter Ankit Agarwal, Ph.D. "A significant finding of the study is that it is indeed possible to design silver-loaded polyelectrolyte multilayers that exhibit antimicrobial activity while allowing attachment and spreading of mammalian cells.”

Silver is widely used as a biocidal agent in ointments and wound dressings. However, typical loadings of silver employed in silver delivery systems can cause tissue toxicity and impaired wound healing, and they have been shown to be cytotoxic to mammalian cells in vitro.

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