Background: Prolonged antimicrobial action of nanocrystalline silver particles incorporated into dressings has revolutionized the treatment of burns and complex wounds. Nearly one million nosocomial infections a year occur in patients with implanted materials and devices. Therefore, we analyzed the antibacterial qualities of polypropylene mesh coated with nanocrystalline silver particles.
Methods: Nanocrystalline silver particles were applied to a polypropylene mesh using physical vapor deposition to make a coated mesh (CM) in three doses: low (0.31 mg/cm²), medium (0.64 mg/cm²), and high (1.13 mg/cm²). The zone of inhibition (ZOI) test consisted of incubating Staphylococcus aureus on agar plates with either a polypropylene uncoated mesh (UM) or a CM. ZOI beyond the mesh was calculated by the difference in area between the ZOI and the mesh. The optical density (OD) test was performed by incubating either UM or CM in medium with S. aureus. A Perkin-Elmer Spectrometer measured the change in OD. Higher OD readings correlated with higher bacterial concentrations. Scanning electron microscopy (SEM) (Geiss 982 FESEM) was used to visualize the surface of UM and CM. Analysis of variance was used to compare the different mesh.
Results:

There was an increasing ZOI for low, medium, and high doses of silver CM and no ZOI for UM (p<0.0001 for all CM compared to UM, Figure 1). The OD test demonstrated an increasing reading for the bacterial medium and UM and a stable OD for low, medium, and high doses of silver CM (p<0.0001). SEM visualized clusters of S. aureus on the surface of UM and no clusters on CM.
Conclusions: The nanocrystalline silver polypropylene CM demonstrated significant antimicrobial activity compared to UM. Coating mesh and other devices with nanocrystalline silver particles may decrease infection rates of patients receiving surgically implanted materials for both urological and non-urological diseases. In vivo studies are ongoing.

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