PAPERmaking! g FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 1, Number 1, 2015
adsorption of Nanosilver led to higher anti-microbial effects in handsheets. Also, turbidity in samples including Staphylococcus aureus was lower. As a rule, Gram-positive bacteria are more sensitive to Nanosilver particles than Gram-negative bacteria due to a difference in the cell walls. In Gram-positive bacteria, the cell wall is rich in mucopeptide component, while in Gram-negative ones the cell wall just contains a thin layer of mucopeptide and is primarily composed of lipoproteins and lipoprotein polysaccharides. Therefore, Escherichia coli shows more resistance to antibacterial materials (Tassou and Nychas 1995). The present findings confirmed the other results reported by Sondi et al . (2004) and Giange et al . (2004). It is clear in Figure 8 that treated paper showed higher resistance to bacteria than the reference samples.
Figure 8. Effect of CPAM and Nanosilver in Banknote paper on turbidity of bacterial medium Microscopic Investigation Figure 9 shows the optical microscope images of papers on the solid culture in the vicinity of bacteria. As can be seen, Esherichia coli was able to grow more abundantly and closer to paper due to greater resistance to Nanosilver than Staphylococcus aureus . Therefore, the inhibition zone in S. aureus was larger. These images confirm the results of the previous section. The present findings are consistent with the results of Haji Mirza Baba et al . (2011). The results provide evidence of the reaction mechanism of Nanosilver with biological macromolecules, inhibition zone formation, and also the transformation of microorganism by conversion of SH bond of proteins that are present on the bacterial surfaces. These proteins give rise to a bulge in the outside of cell membranes and allow passage of nutrients through the cell wall (Baumgartner and Cooper 1996; Sung Kaworn et al . 2007). In this mechanism, Nanosilver particles release silver ions over time. These ions convert SH bonds to SA-g bonds in the microorganism membrane during the substitution reaction. In this way, Nanosilver particles deactivate protein, reduce
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Article 3 – Hygiene (nanosilver)
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