Table 3.

Summary of the 3D bioprinting studies for bone regeneration.

Bio-ink	Cells	Technique	In Vivo	Results	Ref.
ALG/PVA/HAP	Murine calvaria 3T3-E1 cells	Extrusion-based bioprinting	No	PVA/HAP increase bio-ink rheological properties Good cell viability after printing Low mechanical properties	[77]
Nano-HAP/type I COL	Murine D1-MSCs	Laser-based bioprinting	Calvaria defect rats	Manufacture of scaffolds with two geometries: ring and disk High viability and proliferation after bioprinting Bone regeneration in vivo using disk scaffolds	[78]
RGD-γ-irradiated ALG/nano-HAP pDNA complexes encoding TGF-β3 and BMP-2 growth factors	Porcine BMSCs	Extrusion-based bioprinting + PCL 3D printing	Nude mice	High cell viability using PCL co-printing technique High transfection rates Bone ECM production and mineralization Bone formation, immature osteoid detection, and vascularization in vivo	[79]
Vascular bio-ink: RGD-γ-irradiated ALG/MC/nano-HAP nanoparticles loaded with VEGF Osteoinductive bio-ink: RGD-γ-irradiated ALG/MC/LAP/BMP-2	Porcine BMSCs	Extrusion-based bioprinting + PCL 3D printing	Nude mice and femoral-defect rats	Increased vascularization in nude mice with VEGF gradient scaffolds Bone formation and BMP-2 sustained release with osteoinductive scaffolds in nude mice Increase in vessel volume and new bone formation using both bio-ink-based scaffolds in femoral-defect rats	[80]
Type I COL/TCP	Preosteoblast cells (MC3T3-E1) And human ADMSCs	Extrusion-based bioprinting	No	Highly porous scaffolds Good cell viability and proliferation after bioprinting TCP enhances scaffold mineralization after bioprinting with preosteoblast cells TCP promotes osteogenic markers and gene expression in hADMSCs after bioprinting	[81]
ALG/GelMA/highly angiogenic borate bioactive glass (13-93B3)	Human ADMSCs	Extrusion-based bioprinting + PCL 3D printing	No	Glass enhances scaffold stability after bioprinting by promoting alginate–GelMA crosslinking Glass solutes induces a pH increase in the media that is toxic to cells	[82]
ALG/GO	Human MSCs	Extrusion-based bioprinting	No	GO enhances bio-ink’s rheological properties Printability and scaffold mechanics are improved by GO GO protects cells from oxidative stress and promotes their differentiation to bone	[83]
ALG/Gel/GO	Human BMSCs	Extrusion-based bioprinting	No	GO increases printability and scaffold fidelity Good cell viability, proliferation, and osteogenic differentiation after bioprinting Higher GO concentrations increase DNA content and mineralization	[84]

Acronyms—ALG: alginate; PVA: polyvinyl alcohol; COL: collagen; HAP: hydroxyapatite; BMSCs: bone marrow stem cells; PCL: polycaprolactone; ECM: extracellular matrix; MC: methylcellulose; LAP: Laponite; TCP: β-tricalcium phosphate; ADMSCs: adipose-derived mesenchymal stem cells; GelMA: gelatin methacrylate; GO: graphene oxide; Gel: gelatin.