Thermal Treatment Effects on Biopolymer Multilayered Thin Films

Abstract

Sterilization is very important for the use of biomaterials in the medical field. This work describes the preparation of chitosan/carboxymethylcellulose thin films with the layer-by-layer deposition technique, and the investigation on the effects that thermal treatments have on them during sterilization. The influence of different heating and sterilization methods on the chemical and physical structure of biopolymer thin films composed of chitosan and carboxymethylcellulose was evaluated. Films were heated in an oven at specified temperatures or autoclaved and their characteristics analyzed with contact angle, profilometry, FTIR, anionic dye uptake and UV-Vis measurements. Results show that, depending on the heating conditions, these thin films may undergo the Maillard reaction that turns the films from being transparent to brownish in color. This reaction may lead to a decrease in the free hydroxyl groups of both carboxymethylcellulose and chitosan and free ammonium groups of chitosan - consequently leading to changes in hydrophilicity and wettability of the film. Temperature effects on the characteristics of the synthetic pre-layer coating composed of poly (diallyldimethylammonium chloride) and poly (sodium 4-styrene-sulfonate) - used to provide a high cationic surface for the deposition of the biopolymer films - were also observed. These findings are of practical interest because biopolymer thin films find a great number of applications where sterilization is a must, such as clinical and medical applications and in the areas of materials science and biotechnology.