Antibacterial multilayer of chitosan and (2-carboxyethyl)-β-cyclodextrin onto polylactic acid (PLLA)

There is a wide demand for new biodegradable materials with innovations to improve the basic functions of traditional food packaging and prolong the shelf life of food, enhancing its security and sensorial properties. Poly (L-lactic acid) (PLLA) is a biodegradable biopolymer used in traditional packaging of food because of its non-toxicity, biodegradability, biocompatibility and transparency. The aim of this work is to modify PLLA films in order to prepare an improved material for food active packaging. For this, PLLA was internally blended with zinc oxide (ZnO) nanoparticles and, it was also superficially modified by the deposition of chitosan (CHI) and beta-cyclodextrins (beta-CD) by layer-by-layer (LbL). These prepared multilayers were characterized by confocal fluorescence microscopy, contact angle measurements, transmission electron microscopy and UV-Vis spectroscopy. On one hand, the proposed multiple modification inhibits polymer-bacterial interactions and improves the biological properties of the PLLA due to the bactericide effect of ZnO nanoparticles and the contact killing capacity of chitosan. On the other hand, the release of the carvacrol incorporated in beta-CDs improves the antibacterial and antioxidant properties of prepared films (more than 95 wt% of totally released carvacrol was released within 14 days). This investigation demonstrates that here specifically modified PLLA films could be promising materials in the new trends of biodegradable and active food packaging.