Fabrication of functional scaffolds for tissue engineering and regenerative medicine applications requires material systems with precise control over cellular performance. 3D printing is a powerful technique to create highly complex and multicomponent structures with well-defined architecture and composition. In this review paper, we explore extrusion-based 3D printing methods (EBP, i.e., Near Field Electrospinning (NFES), Melt Electrowriting (MEW), Fused Deposition Modeling (FDM), and extrusion bioprinting) in terms of their ability to produce scaffolds with bio-instructive properties. These material systems provide spatio-temporal guidance for cells, allowing controlled tissue regeneration and maturation. Multiple physical and biochemical cues introduced to the EBP scaffolds are evaluated in their ability to direct cell alignment, proliferation, differentiation, specific ECM production, and tissue maturation. We indicate that the cues have different impacts depending on the material system, cell type used, or coexistence of multiple cues. Therefore, they must be carefully chosen based on the targeted application. We propose future directions in bio-instructive materials development, including such concepts as metamaterials, hybrid living materials, and 4D printing. The review gathers the knowledge essential for designing new materials with a controlled cellular response, fabrication of advanced engineered tissue, and developing a better understanding of cell biology, especially in response to the biomaterial.

Interest is growing in the use of hydrogels as bone tissue-engineering (TE) scaffolds due to advantages such as injectability and ease of incorporation of active substances such as enzymes. Hydrogels consisting of gellan gum (GG), an inexpensive calcium-crosslinkable polysaccharide, have been applied in cartilage TE. To improve GG suitability as a material for bone TE, alkaline phosphatase (ALP), an enzyme involved in mineralization of bone by cleaving phosphate from organic phosphate, was incorporated into GG hydrogels to induce mineralization with calcium phosphate (CaP). Incorporated ALP induced formation of apatite-like material on the submicron scale within GG gels, as shown by FTIR, SEM, EDS, XRD, ICP-OES, TGA and von Kossa staining. Increasing ALP concentration increased amounts of CaP as well as stiffness. Mineralized GG was able to withstand sterilization by autoclaving, although stiffness decreased. In addition, mineralizability and stiffness of GG was enhanced by the incorporation of polydopamine (PDA). Furthermore, mineralization of GG led to enhanced attachment and vitality of cells in vitro while cytocompatibility of the mineralized gels was comparable to one of the most commonly used bone substitute materials. The results proved that ALP-mediated enzymatic mineralization of GG could be enhanced by functionalization with PDA. Copyright © 2012 John Wiley & Sons, Ltd.

Biomaterials for tissue scaffolds are key components in modern tissue engineering and regenerative medicine. Targeted reconstructive therapies require a proper choice of biomaterial and an adequate choice of cells to be seeded on it. The introduction of stem cells, and the transdifferentiation procedures, into regenerative medicine opened a new era and created new challenges for modern biomaterials. They must not only fulfill the mechanical functions of a scaffold for implanted cells and represent the expected mechanical strength of the artificial tissue, but furthermore, they should also assure their survival and, if possible, affect their desired way of differentiation. This paper aims to review how modern biomaterials, including synthetic (i.e., polylactic acid, polyurethane, polyvinyl alcohol, polyethylene terephthalate, ceramics) and natural (i.e., silk fibroin, decellularized scaffolds), both non-biodegradable and biodegradable, could influence (tissue) stem cells fate, regulate and direct their differentiation into desired target somatic cells.