GRAFTING OF VANILLIN NANOPARTICLES ON NATURAL AND SYNTHETIC POLYMERS SURFACES UTILIZING THE SONOCHEMICAL APPROACH

In this study vanillin, an edible natural flavor and antimicrobial agent, was deposited as nanostructures on synthetic (polyethylene) and natural (chitosan) polymer films utilizing the sonochemical method. The properties and functionality of the active films coated with vanillin nanoparticles (Np) were studied. Fourier transform infrared spectroscopy (FTIR) measurements indicated the presence of the vanillin Np on the films surface. High resolution scanning electron microscopy (HRSEM) measurements revealed homogenously dispersed Nps of 50-170 nm diameter. The water vapor permeability (WVP) of chitosan film was improved by coating with vanillin Np, while for polyethylene film water vapor permability was unchanged. No significant changes in mechanical properties (tensile strain and tensile stress) were observed for coated chitosan and polyethylene films. The antibacterial properties of the vanillin Np coated polymers were tested against Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative) bacteria species. Chitosan films coated with vanillin Np demonstrated total killing of the both bacteria after 24 hours, while chitosan film without coating revealed total killing after 48 hours (chitosan has intrinsic antimicrobial activity). Polyethylene film coated with vanillin Np revealed total killing after 24 hours only for Gram negative bacteria, while uncoated polyethylene did not show antimicrobial activity throughout the experiment. The antimicrobial activity of vanillin powder and vanillin Nps against E. coli bacteria was compared. It was found that vanillin Nps are more effective and demonstrate minimal inhibition concentration of 3 mM (vs 50 mM for vanillin powder).

Grafting of natural generally recognized as safe antimicrobial agents on polymer surfaces is of high practical relevance, for instance, for active packaging of food products.