Bone Tissue Engineering applications. A) Schematic representation of defect bone and tissue engineering approach using cells in a hydrogel scaffold. Created with BioRender.com B) SEM images of bone tissue-engineered collagen scaffold with different percentage of HA functionalization. i) Overview of a scaffold, ii) 30% HA, iii) 50% HA, and iv) 70% HA. Reproduced with permission [170]. Copyright 2017, Wiley-VCH GmbH. C) Formation of 3D bioprinted scaffold for bone tissue engineering with a degradable middle vessel to incorporate HUVECs, allowing for vessel formation and perfusion, which is schematically displayed in i). ii)-iv) show increased osteogenic function in the perfused tissue by alizarin Red, OCN, and RUNX2 visualization. Reproduced with permission [174]. Copyright 2017, Wiley-VCH GmbH. D) Osteogenesis in RGD functionalized alginate gel with bone formation peptide-1 (pep@MSNs-RA), shown by i) OCN and Col1A1 immunostaining and ii) RUNX2 immunostaining, compared to control (UA). Reproduced with permission [175]. Copyright 2018, Elsevier. E) In vivo implantation of self-healing silk fibroin hydrogel modified with calcium phosphate and polysaccharide crosslinking showing healing of the bone in microCT analysis in i) 3D reconstruction and ii) sagittal cross-section views. Reproduced with permission [176]. Copyright 2017, Wiley-VCH GmbH.