Reactive jet impingement bioprinting for in vitro model development

Abstract

3D bioprinting allows for the production of living tissue in vitro through the printing of cells and supporting materials into complex 3D structures. The applications for this are far reaching including the production of microtissues and organs for transplant [1], as well as for drug testing applications. Furthermore there is evidence to show that 3D cell culture models more accurately replicate in vivo conditions than traditional 2D models by more accurately replicating the in vivo microenvironment [2]. Newcastle University have developed a method of inkjet bioprinting known as the Reactive Jet Impingement (ReJI) method. This method allows for deposition of the desired high viscosity, high cellular density gel at a high deposition rate on a drop on demand basis. The aim of this project was to develop this method to increase the throughput capability, and to evaluate the printhead for production of stratified hydrogel co-cultures incorporating multiple cell types, and in printing cells as part of a cancer invasion model Over the course of this work the ability to print high cellular density bioinks (of the order of 107 cells/ml) with a high cell viability was demonstrated and cell viability remained high in both high and low cell density gels. Additionally, culture type did not affect viability as cell viability remained high in printed stratified co-cultures as well as cultures with only one cell type. Cell density was demonstrated to have had a significant effect on maturation rate of 3D printed tissue models, with higher cell densities producing tissue models with greater extracellular matrix content. This was assessed quantitatively through imaging and qualitatively through ELISA analysis and mechanical testing. The ReJI system was demonstrated to be capable of printing on delicate, uneven surfaces of unknown stiffnesses through printing on sectioned liver tissue slices for use in a cancer invasion model.