Antimicrobial effect and toxicity of cellulose nanofibril/silver nanoparticle nanocomposites prepared by an ultraviolet irradiation method

The objective of this study was to synthesize a novel antimicrobial cellulose nanofibril/silver nanoparticle (CNF/AgNP) nanocomposite by an ultraviolet (UV) irradiation method and evaluate the toxicity of the nanocomposite to human colon cells. AgNPs coated on CNFs have an average size of (similar to)28 nm and exhibited a surface plasma resonance absorption peak at 402 nm. Coating AgNPs on CNFs interfered with the formation of intra-chain and inter-chain hydrogen bonds of cellulose. Moreover, the CNF/AgNP nanocomposite exhibited significant antimicrobial activities against two important food-borne pathogens, including Escherichia coli O157:H7 and Staphylococcus aureus. No apparent toxicity of the CNF/AgNP nanocomposite to Caco-2 and FHC human colon cells was observed, except when a high content of (>= 500 mu g/m L) of the nanocomposite was used for which a significant decrease of cell viability was observed. The nanocomposite's toxicity was related to the content, size, and surface charge of UV-synthesized AgNPs on CNFs. These results indicate that the antimicrobial CNF/AgNP nanocomposite prepared by UV irradiation method can be potentially used as an active filler applied in food packaging materials.