Bioinks for extrusion-based bioprinting: A systematic review of rheology, applications and future directions

Bio-additive manufacturing is a technology that allows scaffold creation for bioengineering applications. Among various techniques, extrusion-based bioprinting (EBB) results as the main process in this field due to a huge versatility as revealed by the possibility to use numerous materials from natural, synthetic or both sources. EBB is first explained reporting strengths and weaknesses through the definition of crucial concepts, such as shape fidelity. Then, a systematic literature review is performed according to the PRISMA methodology to achieve the final eligible number of papers considered during a period of more than 10 years. In this study, hydrogels derived from different origins are reported, highlighting their characteristics from mechanical, biological and manufacturing point of view. Final considerations related to the points to act on to overcome current limitations of this promising technique are presented from a critical point of view, reporting the main undertaken solutions to improve the entire field of regenerative medicine.