A facile method for the deposition of volatile natural compound-based nanoparticles on biodegradable polymer surfaces

In the current work, stable nanoparticles (NPs) of vanillin are formed in situ from an aqueous/ethanol solution and deposited on the surface of chitosan, a natural polymer, using a high-intensity ultrasonic method. The spectroscopic, physical, mechanical and morphological properties of the coated chitosan films are examined by helium-ion microscopy (HIM), atomic-force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), UV-vis spectroscopy, X-ray diffractometry (XRD), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and texture analysis, and compared with the original film properties. Vanillin NPs were detected on the film surface. It was also found that the sonochemical deposition method does not affect the bulk properties of the chitosan films. All the chitosan films demonstrated antimicrobial activity against Gram-negative and Gram-positive bacteria. The deposition of vanillin NPs on the chitosan film also leads to significant antibiofilm activity, especially against the biofilm formation of Escherichia coli bacteria. The in vivo antimicrobial effect of the modified chitosan films was examined on fresh-cut watermelon, melon and strawberry. Vanillin NP-coated chitosan films led to inhibition of total microbial growth and the substantial inhibition of mold and yeast on the fruit. This research can serve as a platform for the development of a mild and effective method for the activation and modification of natural polymers for their future application in biomedical devices and biodegradable active packaging materials.