Chitosan modified with bio-extract as an antibacterial coating with UV filtering feature

Benzophenone-3 grafted chitosan (CS-BP-3) was successfully synthesized and applied as an antibacterial coating for the first time. The grafting mechanism is based on the reaction between ketone and primary amine to form imine derivatives and the chemical structure of grafted chitosan was studied by Fourier transform infrared (FT-IR) spectroscopy. Water solubility of BP-3 is enhanced after covalently grafted on chitosan and consequently renders the chitosan coating with UV blocking property. Results of thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) further confirmed the thermal stability of BP-3 modified chitosan is enhanced. The CS-BP-3 coating was applied on a variety of substrates of glass, plastics, wood, and metal. The surface features of the coatings such as morphology, water contact angle (WCA), and surface roughness were investigated. The optical and thermal stabilities of the coatings under UV irradiation were studied for 16 h. Antibacterial activity of CS-BP-3 was evaluated against both Gram-negative and Gram-positive bacteria. And the results of bacterial inhibition by CS-BP-3 coating indicate its potential for future application in food packaging.