Effects of Hydrodynamic Diameter of Nanoparticles on Antibacterial Activity and Durability of Ag-treated Cotton Fabrics

In this paper, silver nanoparticles (Ag-NPs) colloidal suspensions with different particle sizes of 5 to 40 nm were prepared. Dynamic light scattering (DLS) technique showed that the average hydrodynamic diameters of Ag-NPs were much larger than the particle diameters obtained using transmission electron microscopy and UV-Vis spectroscopy. The as-prepared Ag-NPs with different average hydrodynamic diameters were incorporated in cotton fabrics by the pad-dry-cure method. The silver content before and after washing cycles were determined by inductively coupled plasma spectrometry (ICP). The antibacterial properties of the fabrics after 0, 5 and 10 laundering cycles against both the Gram-negative bacterium ofEscherichia coli(E. coli) and the Gram-positive bacterium ofStaphylococcus aureus(S. aureus) were examined and a clear volcano trend was observed between the bacterial reduction rate (BR) and the hydrodynamic diameter of Ag-NPs loaded on the fibers. The cotton fabric treated by the Ag-NPs with the hydrodynamic diameter of 52 nm, exhibited the highest antibacterial activity (about 98 %) after 10 laundering cycles, while the other samples on either side of the volcano were less active. The cytotoxicity of the cotton fabrics treated with Ag-NPs was assayed on mouse embryonic fibroblast cells and evaluated by an MTT assay. The results showed that Ag-NPs were not toxic. Field emission scanning electron microscopy (FESEM) obtained from the cotton fabric before and after washing cycles demonstrated that the Ag-NPs had tight bonds with the surface of cotton fabric.