Green Bioprinting with Layer-by-Layer Photo-Crosslinking: A Designed Experimental Investigation on Shape Fidelity and Cell Viability of Printed Constructs

Abstract

Process variables of bioprinting (including extrusion pressure, nozzle size, and bioink composition) can affect the shape fidelity and cell viability of printed constructs. Reported studies show that increasing extrusion pressure or decreasing nozzle size would decrease cell viability in printed constructs. However, a smaller nozzle size is often necessary for printing constructs of higher shape fidelity, and a higher extrusion pressure is usually needed to extrude bioink through nozzles with a smaller diameter. Because values of printing process variables that increase shape fidelity can be detrimental to cell viability, the optimum combination of variables regarding both shape fidelity and cell viability must be determined for specific bioink compositions. This paper reports a designed experimental investigation (full factorial design with three variables and two levels) on bioprinting by applying layer-by-layer photo-crosslinking and using the alginate-methylcellulose-GelMA bioink containing algae cells. The study investigates both the main effects and interaction effects of extrusion pressure, nozzle size, and bioink composition on the shape fidelity and cell viability of printed constructs. Results show that, as extrusion pressure changed from its low level to its high level, shape fidelity and cell viability decreased. As nozzle size changed from its low level to its high level, shape fidelity decreased while cell viability increased. As bioink composition changed from its low level (with more methylcellulose content in the bioink) to its high level (with less methylcellulose content in the bioink), shape fidelity and cell viability increased.