Biobased AntimicrobialCoatings: Layer-by-Layer AssembliesBased on Natural Polyphenols

Natural polyphenols possess inherent defensive properties against pathogens. This study investigated the radical scavenging and antimicrobial activity of biobased polyphenol nanoparticles (PNPs) derived from grape seeds. Scanning electron micrographs and dynamic light scattering confirmed the synthesized nanoparticles’ spherical shape, showing an average hydrodynamic radius of 93.9 ± 4.0 nm. The PNPs exhibited radical scavenging activity at about 433 mg Trolox per gram and a microbial inhibitory effect against Micrococcus luteus and Escherichia coli. The negatively charged PNPs were used to prepare thin multilayer films combined with positively charged polyelectrolytes such as poly(allylamine hydrochloride), poly-l-lysine, poly(diallyldimethylammonium chloride), or polyethylenimine. The viscoelastic properties of polyelectrolyte/PNP films were monitored using a quartz crystal microbalance with dissipation. The PNPs showed the best interface compatibility with poly-l-lysine (PLL), enabling the preparation of mechanically stable thin multilayer films. The antioxidant activity of PLL/PNP films was 72 ± 6 μg Trolox per cm² at pH 10. The PLL/PNP films displayed antimicrobial activity against M. luteus and E. coli, with growth inhibition of 50.7 ± 0.6% and 12.1 ± 0.6%, respectively. The prepared biobased PLL/PNP Layer-by-Layer assemblies can potentially prevent biofilm formation on a large spectrum of materials.