Originally Published EMDM January/February 2002
TECHNOLOGY NEWS
MaterialsStable Matrix Enables Use of Antimicrobial Systems in Range of Polymers
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| Wells Plastics used a zone-of-inhibition method to show the effectiveness of antimicrobial synthetic fibres against five bacteria: Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus agalactiae, and Stenotrophomonas maltophilia. |
A compounder of additive master batches has developed a technology that encapsulates silver ion antimicrobial systems within a soluble matrix. According to Wells Plastics Ltd. (Stone, Staffs, UK), the silver ion formulations can help reduce infection in wound dressings, urinary catheters, and other medical applications.
"The silver ions are locked in the matrix and are only released as the matrix is gradually hydrolyzed when it comes into contact with moisture," says chemist Julie Simmons. The matrix, which protects the silver ions during processing and controls their release, is sufficiently stable to allow the system's use in a range of polymers. Its chemical flexibility enables products to be designed for specific applications; particle size and chemical resistance can be modified, and different metal ions can be specified. By altering the solubility of the matrix, varying rates of ion release can be achieved.
The silver ion systems have low toxicity, as validated by US FDA 510(k) approval of one product that uses the technology, notes Simmons. "Film containing one of these systems has also passed 90/128/EEC, the directive on migration limits for plastic materials and articles that come into contact with food products," she adds.
Tests conducted by Wells Plastics on polymeric tubing and fibres have shown the efficacy of the antimicrobial systems.
Plastic tubing containing 2% of a silver ion master batch was tested against Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli. Against initial inoculum concentrations of 10,000 to 80,000 bacteria, the tubing achieved reductions of log 3, or 99.9%, reducing each of the three bacteria populations to <100 colony-forming units.
Synthetic fibres for a wound-dressing application were manufactured with the inclusion of a rapid-release silver ion system, which enabled the fibres' efficacy to be assessed using a zone-of-inhibition method. The accompanying photograph shows clear zones of inhibition against four gram-positive organisms. Subsequent viable count testing established that the antimicrobial fibres were also effective against gram-negative bacteria.
Norbert Sparrow
Copyright ©2002 European Medical Device Manufacturer
