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Influence of Ionic Strength and Anion Type on the Properties of Chitosan-Carboxymethylcellulose Nanofilm

Polyelectrolyte multilayer films based on natural polymers, such as polysaccharides, polyaminoacids and proteins are interesting due to their intrinsic properties such as biocompatibility and non-toxicity to humans. Combined with antibacterial and antifungal properties, such nanofilms could be used as protective agents in medicine and food packaging industry [1]. It is known that antibacterial activity of the nanofilms arises from its morphology and thickness [2], which in turn depends on the conditions of the solution in which they are prepared as well as the type of the surface they are grafted on [3]. In order for the nanofilms to be successfully used as food packaging materials their growth and preparation method has to be predictable and somewhat affordable. Compared to polyaminoacids and proteins, polysaccharides such as chitosan (CHI) and carboxymethylcellulose (CMC) are not expensive because they are derived from an abundant source. In our study, CHI-CMC multilayers were prepared by layer-by-layer (LbL) technique on silicon wafers (Si-SiO2) and titanium plates (Ti-TiO2) as solid surfaces. For both surfaces the growth regime of the CHI-CMC film has been studied by ellipsometry. After dissolution of the polyelectrolytes the pH has been adjusted to desired value and different sodium salts have been added to examine the thickness dependance on both ionic strength and anion type. The surface morphology, more precisely roughness of the final layer and porosity of the film has been determent by atomic force microscopy (AFM) in tapping mode. The thickness of the films obtained by ellipsometry has been confirmed with AFM measurements by comparing the height of the film relative to the solid surface. It was shown that both anion type and ionic strength influence the growth of CHI-CMC multilayers. The obtained results could be helpful for designing polyelectrolyte multilayers with tuned properties, especially suited for applications in the field of medicine.

polyelectrolyte multilayers ; ellipsometry ; atomic force microscopy ; chitosan ; carboxymethylcellulose

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