Structural investigation of chitosan-based microspheres with some anti-inflammatory drugs

► Chitosan hydrogels carrying some anti-inflammatory drugs were prepared. ► Their structural characterization was performed by spectroscopic techniques. ► Antioxidant activity for the supramolecular cross-linked assemblies was determined. ► Drug molecules are forming temporary chelates in chitosan hydrogels and sponges. The use of chitosan as an excipient in oral formulations, as a drug delivery vehicle for ulcerogenic anti-inflammatory drugs and as base in polyelectrolyte complex systems, to prepare solid release systems as sponges was investigated. The preparation by double emulsification of chitosan hydrogels carrying diclofenac, acetyl-salycilic acid and hydrocortisone acetate as anti-inflammatory drugs is reported. The concentration of anti-inflammatory drug in the chitosan hydrogel generating the sponges was 0.08 mmol. Chitosan-drug loaded sponges with anti-inflammatory drugs were prepared by freeze–drying at −60 °C and 0.009 atm. Structural investigations of the solid formulations were done by Fourier-transformed infrared and ultraviolet-visible spectroscopy, spectrofluorimetry, differential scanning calorimetry and X-ray diffractometry. The results indicated that the drug molecules are forming temporary chelates in chitosan hydrogels and sponges. Electron paramagnetic resonance demonstrates the presence of free radicals in a wide range and the antioxidant activity for chitosan-drug supramolecular cross-linked assemblies.