Pérez-Altamar, Melina L.

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    Synthesis and characterization of Chitosan/Cellulose-Zno Nanocomposites for bacterial aplications
    (2016) Pérez-Altamar, Melina L.; Perales-Pérez, Oscar J.; College of Agricultural Sciences; Román, Félix R.; Orellana, Lynnette; Rivera, Aixa; Department of Food Science and Technology; Méndez, Rafael
    The use of non-biodegradable plastics used in food packaging has generated a major environmental concern because of the waste generated. Besides, microbial contamination of food is a serious problem affecting the human health and the food industry. An alternative to face these concerns is the use of biopolymers-based nanocomposites, which are biodegradable and can be modified to provide protection against bacteria based on the tenability of their functional properties. On this basis, the present work focuses on the fabrication of chitosan/cellulose films hosting environmental friendly ZnO nanoparticles (NPs) as an attempt to produce nanocomposites with enhanced bactericidal capacity. Doping nanostructures is an efficient method of control and enhance their properties; it has been suggested that Mg doping influenced the bactericidal capacity of ZnO while enhancing UV blocking capacity. The solution casting method was used to fabricate the chitosan/cellulose blend films at various chitosan/cellulose w/w ratios. Highly monodisperse Mg doped ZnO nanoparticles were synthesized using Zinc acetate, Magnesium acetate and Triethylene glycol (TEG) via a modified Polyol route. The nanoparticles were inserted in the polymeric matrix at different weight percentages. Optical properties of ZnO nanoparticles, pure and Mg-doped, were studied by UV–Vis Spectroscopy and Photoluminescence Spectroscopy (PL) techniques. The nanoparticles’ size and morphology were determined by X- ray diffraction and Scanning Electron Microscopy (SEM). The chitosan/cellulose blend films and chitosan/cellulose- ZnO-Mg nanocomposites were characterized by Fourier Transform – Infrared spectroscopy (FTIR). The mechanical properties of produced bare and ZnO-bearing composites were determined from stress-strain tests. The Standard Plate Count methods was used to evaluate the bactericidal properties of the pure and Mg-doped ZnO nanoparticles and chitosan/cellulose/ZnO-Mg nanocomposites against Escherichia coli. The results reveal the formation of spherical nanoparticles of zinc oxide with a crystalline structure wurtzite and a crystal size in a range from 6 to 8 nm. The higher bactericidal capacity against E. coli was obtained for nanoparticles with a magnesium doping level of 0.5 at. %. In addition, all synthesized nanoparticles exhibited singlet oxygen generating capacity. Films made with chitosan and cellulose showed greater deformation when compared with the chitosan film. The tensile strength and water vapor permeability of the films increased with the insertion of the nanoparticles in the polymeric matrix. All nanocomposites formed by chitosan, cellulose and Mg-ZnO nanoparticles exhibited high bactericidal capacity against E. coli.