CHEMICAL MODIFICATIONS OF COTTON TEXTILES
Location: Cotton Chemistry and Utilization Research
Title: Silver(I) Antimicrobial Cotton Nonwovens and Printcloth
Submitted to: Polymers for Advanced Technologies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 2006
Publication Date: June 6, 2007
Citation: Sachinvala, N., Parikh, D.V., Sawhney, A.P., Chang, S., Mirzawa, J., Jarrett, W., Joiner, B. 2007. Silver(I) Antimicrobial Cotton Nonwovens and Printcloth. Polymers for Advanced Technologies. 18:620-628.
Interpretive Summary: Silver has been used as an antimicrobial agent for over 2000 years. The Romans and the Arabs kept silver coins in their water bags to keep their drinking water fresh. Silver nitrate has historically been used as an antiseptic agent as it has a broad antibacterial spectrum and is effective against most strains; this method was at one time a mainstay in the treatment of burns. In the Middle Ages, it was often used to destroy dead or unwanted tissue to prevent the spread of infection. Topical use of Ag (I) ions remains popular in the treatment of skin wounds and infections. Many Ag (I) dressings are available today and they include: Ag (I) ions on activated carbon and absorbent alginates, and Ag (I) coordinated with carboxymethyl (CM) cellulose. Yet, there remains a need for low-cost dressings that can serve many needs and it appears that CM cotton wovens, nonwovens, and composites are well suited for such applications. We evaluated the antimicrobial properties of alginate and cotton fabrics against Gram-positive Staphylococus aureus, Gram-negative Klebisiella pneumoniae by challenging inoculums with silver containing fabrics, and determined them as excellent antimicrobials. From the present work we realize that CM-cottons offer useful functional properties at low cost for exchanging a wide variety of cations for use as dressings in the healing of burn and chronic wounds, and ulcers.
In this paper we discuss the preparation and comparative evaluation of silver (I) [Ag(I)] nonwoven and woven antimicrobial barrier fabrics generated from commercial calcium-sodium alginates and laboratory prepared sodium carboxymethyl (CM) cotton nonwovens and CM-cotton printcloth for potential use as wound dressings. Degrees of CM substitution (DS) in cotton nonwoven and printcloth samples by titrimetry were 0.38 and 0.10, respectively. Coordination of Ag(I) with carboxylates on fabrics was effected by ion exchange and nitrates were removed by washing to mitigate nitrate ion toxicity issues. Durability of silver coordinated fabrics was tested by soaking them in deionized water with slight agitation at 50-C. Ag(I) alginates and nonwoven Ag(I)-CM-cottons lost structural integrity in water. Ag-CM-cotton printcloth samples retained structural integrity even after four soak-and-dry cycles, were smooth to the touch when dry, and were smoother when moistened. They could be easily peeled from wound surfaces without inducing trauma. Solid-state carbon-13 (13C) nuclear magnetic resonance (NMR) spectrometry was used to observe changes in carbonyl resonances in Ag(I) alginates and Ag(I)-CM-printcloth, and the chemical shift positions of carbonyl resonances of uncoordinated and Ag(I) coordinated fabrics did not change. Inductively coupled plasma-mass spectrometry (ICP-MS) was used following fabric digestion to determine the total Ag(I) ion content in fabrics. Ag(I) alginates were found to hold about 10–50mg Ag(I) per gram fabric; and Ag(I) cotton woven and nonwoven fabrics held about 5–10mg Ag(I) ions per gram fabric. Kinetic release of Ag(I) after soaking once in physiological saline was studied with ICP-MS to estimate the availability of Ag(I) upon a single exchange with Na(I) ions on wound surfaces. Alginates released between _13 and 28% of coordinated Ag(I), and CM-cotton nonwovens and CM-cotton printcloth released _14 and 3% of coordinated Ag(I) ions, respectively. Finally, Ag(I) alginates and Ag(I)-CM-cotton printcloth samples were evaluated against Grampositive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae. Ag(I) alginates suppressed 99.95% of bacterial growth in vitro. Even after four soak-and-dry cycles in deionized water Ag(I)-CM-cotton printcloth suppressed 99.99% of bacterial growth in vitro.