3D printing of soft hydrogels incorporating functional nanomaterials

Abstract

Tissue engineering (TE) scaffolds are required to closely mimic the human body environment to enable the study of cell behavior in vitro and allow the fabrication of artificial tissue constructs. The scaffolds should possess controlled structural and mechanical properties, such as stiffness and porosity. In addition, its physical and chemical properties, such as electrical conductivity, should be able to promote cell differentiation and growth. In the search of developing an ideal scaffold, hydrogels that incorporate functional nanomaterials scaffolds are being explored. This study, as a fulfillment for a master’s degree, investigates the ability of cells to survive in a three-dimensional (3D) printed soft hydrogels incorporated with functional materials. In this work, alginate, a natural polymer, was used as the main hydrogel material. It can physically crosslink by adding CaCl2 or chemically crosslink after methacrylation, by introducing carbon-carbon double bonds. However, pure alginate hydrogel is mechanically and rheologically weak. Previous mechanical tests indicated that cellulose nanocrystals (CNC)-incorporated alginate-based hydrogels increased the mechanical strength of the scaffolds, which can contribute to the interactions between CNC and polymeric networks. Rheological tests showed that the incorporation of cellulose nanocrystals into the alginate matrix introduced strong shear thinning behavior and improved shear modulus. The enhancement of rheological properties improved the printability and fidelity of the hybrid pre-gel solution. Finally, cell viability was explored by suspending 3T3 fibroblasts in the bioink. It was shown that the hybrid bioink was nontoxic and the cell viability remained high over a 7-days period. This master’s thesis demonstrates the feasibility of 3D printing of soft hydrogels for the fabrication of 3D scaffolds that mimic real tissues. It is anticipated that a broad array of ink compositions with suitable viscosity can be printed and multiple cell lines can grow in the same scaffold. This research provides a platform for the fabrication of biocompatible polymers and stretchable biosensors within an engineered scaffold.