(656a) Synthesis and Characterization of Environmentally-Benign Silver Ion/Lignin Antimicrobial Nanoparticles

The introduction of antimicrobial silver nanoparticles (AgNPs) in industrial applications may lead to persistent and potentially toxic nanowaste in the environment. We will present a new class of antimicrobial environmentally-benign nanoparticles (EbNPs) designed with green chemistry principles, which can serve as highly efficient microbicidal substitutes of the AgNPs. The EbNP core is made of biodegradable lignin, and is infused with an optimal amount of silver in the form of adsorbed Ag⁺ ions. We show that Ag⁺ ion functionalized EbNPs exhibit higher antimicrobial activity towards Gram-negative human pathogens Escherichia coli and Pseudomonas aeruginosa in direct comparison with silver nanoparticles and silver nitrate solution. The EbNps are also effective against quaternary ammonium resistant Ralstonia species. The enhanced antimicrobial action is due to highly biocidal Ag⁺ ions released from the EbNP adhered to the cell. The functionalized EbNPs exhibit broad spectrum biocide action, while using 10× less silver when compared with conventional AgNPs and AgNO₃ aqueous solution. These particles are fabricated by environmentally friendly water-based acid precipitation methods. We obtained EbNPs with diameters ranging from 40 to 200 nm and with pH stability ranging from pH 4.0 to 9.0. High-throughput bioactivity screening using mammalian cell and zebra fish embryo assays performed in collaboration with the U.S. Environmental Protection Agency (US EPA) did not reveal increased toxicity of the EbNPs, when compared to equivalent amount of AgNPs or AgNO₃ solution. The EbNP synthesis illustrates how green chemistry principles including atom economy, use of renewable feedstocks, and design for degradation can be applied to design more sustainable nanomaterials with increased functionality and decreased environmental footprint. This abstract does not necessarily reflect US EPA policy.