RADIATION-CLEAVABLE MICROPARTICLE CHAPERONES FOR DURABILITY-CONTROLLED NANOCOMPOSITE BIOPLASTICS

Polysaccharide micro/nanoparticles, incorporating stabilizers (natural antioxidants), prodegrading agents (such as enzymes or metal oxide nanoparticles) or other active ingredients, can be considered ideal chaperones to introduce various and heterogeneous substances into polysaccharide films in virtue of their structural affinity. The possibility of obtaining biodegradable and colloidally stable nanoparticles from xyloglucan has been here investigated. Xyloglucans are a major class of structural polysaccharides found in the primary cell walls of higher plants. They are particularly interesting raw materials for their excellent film forming properties, thermal stability and hydroxyl rich, highly branched molecular structure, which controls hydrophobicity and solubility characteristics and, thereby, temperature or solvent responsiveness. If the branching degree and molecular weight are properly modified, stable xyloglucan nanoparticles dispersions can be obtained. During the first part of this CRP protocols for xyloglucan purification and dispersion in water in the form of stable colloids have been developed. 60Co γ irradiation has been applied to modify the molecular weight distribution of a partially degalactosylated xyloglucan variant. Aqueous dispersions of the irradiated materials have been characterized by both dynamic light scattering measurements at different temperatures and gel filtration chromatography. The aggregation kinetics at 37°C of nonirradiated and irradiated variants have been studied by dynamic light scattering measurements in order to confirm their temperature-responsive behavior, when dispersed in water at low concentration. Chemical modification of xyloglucan with nitrocinnamic acid has been performed in order to graft nitrocinnamate pendant groups through an esterification reaction, thereby inducing reversible photocrosslinking. The success of the reaction has been confirmed through UV-vis and FTIR spectroscopies, whereas a more quantitative estimation of the derivatisation degree is undergoing.