Characterisation of chitosan after cross-linking by tannic acid

Chitosan is widely applied in biomedical and cosmetic fields. For this reason, there is a need to modify this biopolymer to achieve new properties of chitosan-based materials. The properties of chitosan can be modified by several cross-linking methods. In this work, we used the chemical cross-linking of chitosan with tannic acid, after which cross-linked chitosan was shaped into a 3D structure by the lyophilisation process. For the material obtained, FTIR-ATR analysis was performed to characterise the structure of cross-linked chitosan. Moreover, mechanical properties and swelling properties were measured for chitosan before and after cross-linking. The results show that several properties of chitosan can be changed after cross-linking by tannic acid. The positions of bands in the FTIR spectra of chitosan were shifted after cross-linking. Mechanical properties were altered for cross-linked chitosan. However, the highest compressive modulus was observed for pure chitosan. The lowest compressive modulus was observed for chitosan cross-linked with 20 wt% of tannic acid. Swelling behaviour also depends on the cross-linking of chitosan. It decreases for chitosan after cross-linking by tannic acid. Overall, the properties of cross-linked chitosan depend on the amount of tannic acid used for modification. This method of cross-linking can be useful for obtaining materials with specific properties.