Structural analysis of chitosan hydrogels containing polymeric nanocapsules

• The polymeric nanocapsules are initially agglomerated in the chitosan hydrogels.
• The nanocapsules caused a decrease in the degree of chitosan chains entanglement.
• High amounts of nanocapsules led to a reorganization of the microdomains.
• Sedimentation of nanocapsules and physical interaction with chitosan were verified.
• The gels presented shear-thinning and elastic properties, besides structured network.

The incorporation of different concentrations of polymeric nanocapsule suspensions into chitosan hydrogels is proposed, in order to study the structure of a formulation with the properties of great tissue adhesion and controlled release of the nanoencapsulated drugs, represented here by capsaicinoids. The gels presented acceptable acid pH values and the nanoparticles were visually observed in the system. A transition from the micrometer to the nanometer scales suggested that the nanocapsules are initially agglomerated in the hydrogel. A sedimentation tendency of the nanocapsules in the system was observed and only physical interaction between the chitosan chains and polymeric nanocapsules was verified. The hydrogels, despite the presence of nanocapsules, presented shear-thinning properties and an elastic behavior under low and high frequencies, showing a very structured gel network. The observed variation in the elasticity of the hydrogels may arise from a decrease in the number of interactions and degree of entanglement between the chitosan chains, caused by the presence of nanoparticles.

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