Journal of Photochemistry and Photobiology A: Chemistry
Antibacterial textiles prepared by RF-plasma and vacuum-UV mediated deposition of silver
Introduction
Silver has been known as a disinfectant for many years and is being used in many forms in the treatment of infectious diseases [1], [2], [3] and has a broad spectrum antibacterial activity while exhibiting low toxicity towards mammalian cells. In a very low concentration silver-ions are effective against bacteria in water systems [4], [5]. The mechanism of silver antibacterial action is poorly understood. Three mechanisms for the latter effect have been proposed: (a) interference with bacterial electron transport; (b) binding to the bacterial DNA after in low concentration Ag enters the cell. As a reaction against the denaturation effect of Ag/Ag-ions, DNA condenses loosing their replication ability [6] or interacts with protein thiol groups inactivating the latter; and (c) interaction with cell wall membrane without entering the cell forming reversible sulfhydryl or histidyl complexes on the cell surface and preventing dehydro-oxygenation process [7], [8], [9].
This investigation is directed towards the fixation and catalytic performance of Ag-clusters on polyamide–polystyrene textile fabrics. After a long series of preliminary experiments, the most suitable experimental conditions for the RF-plasma and vacuum-UV (V-UV) activation of the fabric surface were found. Then the chemical deposition of Ag-clusters was carried out on these activated surfaces checking subsequently each Ag deposit against the antibacterial activity observed. Once the optimization of the Ag-clusters was completed the latter clusters were characterized by complementary surface techniques like: diffuse surface reflectance (DRS), elemental analysis, X-ray photo-electron spectroscopy (XPS), and transmission electron microscopy (TEM).
Section snippets
Materials
Reagents like AgNO3, ammonia, isopropanol, Ag2CO3 were Fluka p.a. and used without further purification. Deionized water was employed throughout this work.
Functionalization of textile fabrics by RF-plasma
The textile polymer fabric surface was treated in a RF-plasma cavity (Harrick Corp., 13.56 MHz, 100 W) at a pressure of 0.8 Torr. A variety of oxygen functional groups: CO, CO,OCO, COH, COOH were produced on the fabric through the reaction between the active species induced by the plasma in the gas phase and the C-surface atoms [10].
Biological testing of the Ag-loaded textile prepared by RF-plasma activation
Fig. 1(a) shows the effect of Ag-loaded textiles surfaces activated by RF-plasma on the airborne bacteria after 24 h. The antibacterial effect reported in Fig. 1(a) was carried out in the dark. Adsorption of bacteria on the textile was observed on the unloaded fabric and as well as on the Ag-loaded fabric. The abscissa refers to the AgNO3 grams in 200 ml solution used in the silver loading after the RF-plasma treatment. After the relative index of 0.3 g AgNO3/200 ml solution (Fig. 1 trace (A)), the
Conclusions
This study has shown the beneficial antibacterial activity of silver grafted on textile fabrics by RF-plasma and vacuum-UV followed by chemical treatment of the silver salt on the fabric surface. A minimum loading of silver was seen to be necessary to inhibit the airborne bacterial growth depending on the method used to activate the textile surface. This effect was also investigated and reported for aqueous suspensions of E. coli K-12 taken as a bacterial model. The electron microscopy carried
Acknowledgements
The financial support of KTI/CTI TOP NANO 21 (Bern, Switzerland) under Grant no. 5601.1 TNS is appreciated.
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