The Development of Thermally Reversible Chitosan-Containing Hydrogel Ink for Extrusion 3D Printing

The implementation of the process of extrusion 3D printing for solutions of chitosan is complicated in view of the low shape stability of its printed structures, while introduction of a crosslinking agent does not provide immediate formation of an elastic hydrogel after extrusion. The paper proposes a method for obtaining chitosan-containing hydrogel structures by combining agar with chitosan in the composition of printing “ink,” which makes it possible to form a shape-stable material with the biological activity inherent to chitosan. The physicochemical properties of hydrogels based on agar and chitosan as well as their compositions modified with genipin are studied. It is found that introducing chitosan into hot solutions of agar results in a decrease in the temperature and a change in the kinetics of gel formation. The use of genipin as a crosslinking agent makes it possible to obtain resistant to the action of the environment hydrogels suitable for direct extrusion 3D printing (direct ink writing (DIW)). Thermally reversible hydrogel ink with the optimum agar/chitosan ratio are developed which demonstrate good shape stability and high resolution during printing. The obtained results of the work open up prospects for using this system in the field of biomedicine, food industry, and cosmetology.