Bioprinting with bioactive glasses: a review on material design, biological performance and tissue engineering applications

Tissue engineering and regenerative medicine have shown invaluable promises for the repair, recovery or replacement of diseased tissues and organs. Merging the paradigms of these disciplines with additive manufacturing technologies has recently yielded the advent of bioprinting, i.e. the layer-by-layer production of tissue-like porous scaffolds incorporating living cells. While soft biocompatible hydrogels are the ideal matrix for hosting and preserving cells during the printing process, small amounts of additional ingredients (organic or inorganic) can be incorporated in the bioinks to stimulate cell activity and impart extra-functionalities to the overall bio-printed construct. In this regard, bioactive glasses promote cell-matrix interaction and cell biology pathways through the local release of biologically active ions and are also able to elicit a local antibacterial effect which is key to combat post-surgical infections at the bioimplant site. This review aims to provide an up-to-date overview of the use of silicate, borate and phosphate glasses as valuable additives to bioinks for bioprinting applications. Opportunities for further research are highlighted and the challenges that must be tackled to advance this emerging field are discussed. STATEMENT OF SIGNIFICANCE: The biofabrication of a truly functional living tissue or organ in the lab for implantation in the body is one of the grand challenges of regenerative medicine. This hope has materialized with the advent of bioprinting, which allows the incorporation of living cells in a soft supportive matrix by applying additive manufacturing technologies. This review summarizes the state-of-the-art of bioprinting with bioactive glass particles incorporated in the printable ink. The current limitations and the latest evolutions in this exciting field of research are critically examined, and the roles of design parameters (e.g. composition, concentration and size of the bioactive phase) as well as the rheological, mechanical, biological and overall functional performance of such special types of bioinks are detailed. Existing results and new horizons are discussed for providing a comprehensive picture that may be useful for both experienced and early-stage researchers in the biomaterials community.