WEB 3D Printing of Biocompatible Nanocomposites via Genipin-Chitosan Crosslinking
3d printing of living cells that are embedded in hydrogels or in hydrogel nanocomposites is quickly becoming an established strategy for designing materials for tissue engineering or for biotechnological processes. However, it is challenging to design materials that are fully biocompatible and that are also showing long-term stability in biological environments. Particularly the reinforcement of the hydrogel network with covalent bonds can be directly opposed to the viability of the embedded cells. Here, we show a novel strategy for liquid feed extrusion printing of hydrogel/ceramic nanocomposite inks with embedded living bacteria cells. This bioink combines the gelling properties of a chitosan/alginate hydrogel with the structural properties of a percolating alumina particle network. Additionally, the structure is reinforced by covalent crosslinking between the chitosan molecules using genipin. Genipin is a natural molecule extracted from the fruits of Gardenia jasminoides. It has very low toxicity and is able to induce the crosslinking of proteins and polysaccharides via amine groups. Although genipin can potentially also crosslink cellular components of the embedded bacteria, which would be detrimental to their viability, the presence of alginate in the multi-component gel structure seems to prevent excessive loss of living cells. The outcome is a highly stable bionanocomposite material with minimal shrinkage, highly increased structural and mechanical stability over pure hydrogels, long-term stability, as well as excellent biocompatibility. The gels were analyzed regarding their rheology, printability, porosity and degradation characteristics, while the viability, accessibility and productivity of the embedded cells was demonstrated in biological studies. Accordingly, this method shows great potential for producing macroscopic bioactive materials with complex shapes for biomedical and biotechnological applications.