Ricerc@Sapienza

Bioprinting is a tool increasingly used in tissue engineering laboratories. As an extension to classic tissue engineering, it enables high levels of control over the spatial deposition of cells, materials, and bioactive factors. Extrusion bioprinting is the most commonly used technique, where high viscoelastic solutions of materials and cells (bioink) are required to ensure flow through the nozzle and good shape fidelity of the printed tissue construct. However, the encapsulated cells are often restricted in spreading and proliferation by dense biomaterial networks originated from the gelation of bioinks. Bioprinting macroporous hydrogel fibres can handle such a problem by allowing for adequate cell motility and their organization into functional tissues. This project aims to develop aqueous two-phase emulsions where the dispersed phase droplets act as the pores templates, and the continuous phase is photocrosslinked, leading to predesigned cell-laden hydrogel constructs. Such a fully aqueous environment would ensure appropriate mass exchange and good cell survival.
Rotational rheometry is routinely used to assess ink printability and as a guide to ink formulation. However, the flow imposed by currently available instrumentation is not representative of the bioink flow pattern inside an extrusion system, making difficult the correlation between results and bioink printability. Furthermore, rotational rheometry does not allow predicting the effect of extensional and shear stresses at the syringe-nozzle junction and inside the nozzle, respectively, on cell viability. Recent advances in microfabrication and microfluidics have spurred the development of microfluidic viscometers. These instruments require low sample volumes, favouring systematic investigation and generate a flow field replicating that experienced by the bioink during extrusion. These features make microfluidic viscometry a tool particularly suited in the screening of bioink candidates.