Chitin Cryogels Prepared by Regeneration from Phosphoric Acid Solutions

Cryogelation is a developing technique for the production of polysaccharide materials for biomedical applications. The formation of a macroporous structure during the freeze-drying of polysaccharide solutions creates biomaterials suitable for tissue engineering. Due to its availability, biocompatibility, biodegradability, and non-toxicity, chitin is a promising natural polysaccharide for the production of porous materials for tissue engineering; however, its use is limited due to the difficulty of dissolving it. This work describes the preparation of cryogels using phosphoric acid as the solvent. Compared to typical chitin solvents phosphoric acid can be easily removed from the product and recovered. The effects of chitin dissolution conditions on the structure and properties of cryogels were studied. Lightweight (ρ 0.025-0.059 g/cm³), highly porous (96-98%) chitin cryogels with various heterogeneous morphology were produced at a dissolution temperature of 20 ± 3 °C, a chitin concentration of 3-15%, and a dissolution time of 6-25 h. The crystallinity of the chitin and chitin cryogels was evaluated by ¹³C CP-MAS NMR spectroscopy and X-ray diffractometry. Using FTIR spectroscopy, no phosphoric acid esters were found in the chitin cryogels. The cryogels had compressive modulus E values from 118-345 kPa and specific surface areas of 0.3-0.7 m²/g. The results indicate that chitin cryogels can be promising biomaterials for tissue engineering.