Chitosan-gellan electrostatic complexes: influence of preparation conditions and surfactant presence.

Nanoparticles were obtained by electrostatic complexation between chitosan and gellan gum at different polysaccharide ratios. The effect of the chitosan:gellan ratio on the particle charge and particle size distribution was determined by dynamic light scattering measurements. The particle stability was studied during storage in an aqueous medium at 25°C for 100 h. The effect of the preparation procedure (mixing steps) on the characteristics of the complexes was also determined. In addition, the influence of a nonionic surfactant (polysorbate-20) on the chitosan:gellan electrostatic complexes (PECs) was evaluated. The charge of the PECs depended on the polysaccharide ratio. During storage, structural reorganization of the complexes was observed. The mixture protocol was a determinant factor for PEC size. Multilayered particles formed by a 2-step mixing of polysaccharide solutions showed a considerable increase in size as compared to the complexes formed by a 1-step mixing. The PEC size, count rate and zeta potential were not affected by the presence of polysorbate-20.