Chitin nanocrystals-alginate bioinks for bioprinting of 3D structures

Abstract

Bioprinting is a 3D printing technology to deposit layer-by-layer stacking patterns of biomaterials with incorporated viable cells, enabling the production of cells, tissues or organs. Biocompatibility, biodegradability, good cross-linking mechanisms, good rheological and printability are the most important features of a bioink which are typically achieved with polymer hydrogels. Alginate hydrogels have been found much use in bioprinting applications because they are so easily cross-linked, low cost, abundantly available, and have shown good biocompatibility. However, their gel precursor solutions generally present low viscosity and Newtonian flow behavior at low shear-rates (zero shear viscosity), which can lead to deformation of printed constructs after deposition from the needle in the extrusion printing process. These mechanical problems can be overcome adding viscosity modifiers such as nanocellulose and chitin, that will enhance the viscosity of the precursor solutions and will give them a yield point at low shear rates rather than a zero. The main goal of this dissertation is the production and characterization of hydrogels composed by alginate and nanocellulose or chitin nanowhiskers and evaluate its 3D printability as bioinks. Nanocellulose was successfully obtained from acid hydrolysis and was prepared as a aqueous solution with a concentration of 1.9 % wt.. Additionally, chitin nanowhiskers were also successfully obtained from acid hydrolysis and two aqueous solutions were prepared at 1.9 % wt. and 2.7 % wt.. The aqueous solutions were posteriorly mixed with alginate at different proportions in order to study the cross-linking mechanism of the bioinks. 3D structures were printed using “hand-draw” 3D printing and 3D printing techniques resorting the bioinks and cross-linking solutions. This work shows the progress of the printing conditions until successfully printed structures were obtained, using hydrogels and natural resources like cellulose and chitin