Three-Dimensional Extrusion Bioprinting: Process Optimization and Novel Technology Development for Fabricating Skeletal Muscle Tissue

Abstract

Tissue engineering is a multidisciplinary field that utilizes principles of cellular biology, mechanobiology, engineering, material science and medicine to develop tissue-like constructs that can ultimately restore, maintain or improve damaged body tissues. To achieve this, different tissue fabrication techniques have been proposed, among which, extrusion-based three-dimensional (3D) bioprinting has gained significant attention and has stood up as a promising technology. During extrusion-based bioprinting, cells are subjected to mechanical forces of different kinds. Among these mechanical forces, shear stress is of special significance and concern as it is considered the main cause of cell damage/death. This thesis investigated extrusion-based bioprinting induced shear stress in terms of causes, modeling, impact, and potential optimization strategies for preserving cell viability post printing. In specific, two approaches for preserving cell viability post printing were studied. In the first approach, the effect of moderate shear stress preconditioning on the ability of skeletal muscle cells to tolerate bioprinting induced stress was studied. Results demonstrated that exposure to shear stress prior to printing enhanced viability of cells after printing. This novel finding indicates that shear stress cell preconditioning is a promising method to enhance cell viability post printing, which is of vital importance in tissue engineering applications. In the second approach, two novel biocomposite conductive inks composed of low concentration GelMA supplemented with either a metallic nanoparticle (gold nanoparticles, AuNPs) or a two-dimensional (2D) transition metal carbide (MXene nanosheets) were developed, fine-tuned and characterized for 3D bioprinting of highly viable skeletal muscle tissue. Results showed that these developed bioinks allowed for cell spreading and migration, endowed tissue with conductivity which is vital in tissue engineering of excitable cells, and indeed enhanced the differentiation of encapsulated C2C12. Furthermore, by adding AuNPs or MXene and thermally crosslinking GelMA at 10oC, the rheological properties, specifically shear-thinning and yield stress, were substantially enhanced which allowed for printing stable constructs with high cell viability.

Date of Award	Nov 2021
Original language	American English