Title: Swellability of Silver (I) Antimicrobial Wound Dressings Authors
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: February 10, 2010
Publication Date: N/A
Technical Abstract: An important characteristic of moist wound dressings is their ability to swell and absorb exudates from the wound, while maintaining a moist atmosphere at the wound site. At the Southern Regional Research Center, we have developed antimicrobial silver- CM-cotton print cloth from CM-Printcloth with low DS (degree of substitution), and silver alginates from four commercially available alginate dressings. As an ongoing research of silver antimicrobials, this report delineates the swellabilty of silver antimicrobial dressings, commercially available calcium-sodium alginate dressings and printcloth (controls) in water and in 0.9% sodium chloride solution after 8 hours and after one week of immersion. The swelling characteristics were then correlated with the absorption of saline g/g. Four commercially available sterile needlepunched calcium/sodium alginate moist wound alginate felt dressings were: Sorbsan (Bertex Pharmaceuticals, 94.0 g/m2), Kaltostat (ConvaTec, 110 g/m2), Curasorb (Kendall Healthcare, 175 g/ m2), and AlgiSite M (Smith and Nephew, 165 g/m2). Their silver alginates were prepared using non-aqueous medium. Measurements of the diameter of swollen silver antimicrobial alginate dressings in water and in 0.9% NaCl solution, after 8 hrs, and after 1 wk were done using the following procedure: approximately 1 cm2 of the dressing was put into a Petri dish with sufficient water (or 0.9% NaCl solution) and covered. The sample was removed carefully after specified time of immersion and the wet sample was placed on a slide (without a coverslip) and observed with reflected light using accessory fiber optic lights separate from the microscope. The diameters of the dry and wet fibers were either measured directly using an ocular micrometer or from photographs using image analysis. Fiber diameters were measured on four different dates, and the combined data are reported. The data were analyzed statistically and the findings are reported with standard deviations. This research shows that most of the diameter increase occurs within the initial 8 hours of immersion, and continued immersion for a week produces only a modest further increase. In general, silver-alginates swelled less than their controls in either solution at 8 hours and at one week. The data suggest that Sorbsan may be best suited for highly exudating wounds whereas Curasorb for the moderately/less exudating wounds. The swelling of CM-printcloth is much lower than the swelling of alginates. The silver printcloth swelled less than its control. Single fiber measurements were taken to determine if swelling involved increase in diameter as well as length. Fibers were cut to a length approximately 1-2 mm and placed on a slide. The dry fibers were then photographed, and distilled water or 0.9% NaCl was added with a pipette. Single fiber swelling measurements of alginate dressings indicate that fluid absorption led to expansion in the diameter of the fiber but not in the length (true also for the silver CM-printcloth). The saline absorbency of silver antimicrobials (g of saline absorbed per g of the dressing of silver alginate or silver-CM-printcloth) from our earlier research were correlated with the fiber swelling data. Per our earlier findings, the silver antimicrobials are effective against both Gram-positive (Staphylococcus aureus) and Gram-negative (Klebsiella pneumoniae) organisms as determined by Dow Corning Shake Flask Test. Silver antimicrobial dressings with absorptive properties should make them ideal for treatment of exudative wounds that are at risk of infection.