Abstract
In this study, sodium alginate (SA)-based, eco-friendly nanocomposites films were synthesized for potential food packaging applications using silver nitrate (AgNO3) as the metal precursor, reactive nitrogen and oxygen species (RNOS) created within plasma activated water (PAW), or through cold plasma treatment (CP) as reducing agent and SA as stabilizing agent. The formation of silver nanoparticles (AgNPs) was confirmed via the absorption peaks observed between 440 and 450 nm in UV-vis spectroscopy. The tensile strength (TS) and tensile modulus (TM) of the nanocomposite films were significantly higher than those of the SA films. An increase in the TS was also observed as the AgNP concentration was increased from 1 to 5 mM. The storage modulus (G’) of the nanocomposite solution was higher than that of the SA solution. The synthesis of AgNPs resulted both in a higher solution viscosity and a more marked shear-thinning effect. The synthesized AgNPs showed antimicrobial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The AgNPs were spherical in shape with an average size of 22 nm.
Highlights
AgNPs with an average size of 22 nm were successfully synthesized using the reactive nitrogen and oxygen species present in the plasma activated water (PAW), or produced during cold plasma treatment as the reducing agent within sodium alginate (SA) solution, which acts as a stabilizing agent for the nanoparticles
The UV-vis spectroscopy and color change of the solution confirmed the successful synthesis of AgNPs using both processes (PAW and cold plasma)
Irrespective of the silver nitrate concentration and test dose, the nanocomposites prepared using both plasma and PAW treatments significantly inhibited the growth of both bacterial strains
Summary
AgNPs are considered to be a new class of antimicrobials, providing a new means to combat a wide range of bacterial pathogens Due to their high specific surface area, AgNPs are more able to interact with the membranes of bacterial cells [4]. Several studies have reported that AgNPs can damage the cell membrane, leading to structural changes that make the bacterial cell more permeable [5,6] This effect is highly influenced by the size, shape, and concentration of AgNPs. It has been reported that the reduction in the size of AgNPs can lead to an increased antibacterial activity [7,8]. Rautela reported the synthesis of silver nanoparticles in the size range between 10 and 30 nm using tectona grandis seed extracts as the reducing agent [11].
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