Multilayer Chitosan/Lignin Nanocoating with Silver Nanoparticles for Antimicrobial Cotton

Abstract

The demand for antimicrobial textiles is rapidly growing particularly in medical sector. In an effort to develop a simple and efficient antimicrobial treatment for cotton, layer-bylayer deposition of chitosan and magnesium lignosulfonate, followed by in situ synthesis of silver (Ag) nanoparticles, was accomplished. Lignin is exploited as a natural reducing and stabilizing agent1,2, producing Ag nanoparticles in amounts even larger than those obtained with sodium borohydride as a strong reducing agent. The influence of the number of bilayers (4 and 12) and initial concentration of AgNO3 solution (10 and 20 mM) on antimicrobial activity of cotton fabric against Gram-negative bacteria E. coli, Gram-positive bacteria S. aureus, and C. albicans, yeast was examined. The presence of evenly scattered Ag nanoparticles all over the fiber surface is confirmed by FESEM analysis (Figure 1). The number of bilayers does not affect the size of nanoparticles (~56 nm), but an increase of bilayers results in greater Ag content. The samples treated with 20 mM AgNO3 solution contain more Ag than those treated with 10 mM solution. The formation of metallic Ag nanoparticles is confirmed by XPS analysis. Synthesized Ag nanoparticles provide excellent antibacterial activity against bacteria S. aureus (99.9 %), independent of the initial concentration of AgNO3 and number of bilayers. Larger content of Ag nanoparticles i.e., higher initial concentration of AgNO3 solution leads to considerably enhanced antibacterial activity against E. coli. A similar trend is evident with the C. albicans yeast, but the desired yeast reduction of 99 % was not obtained.