Table 1.

Overview of 3D printed neural regeneration devices

Application	Materials	Cell Type	Printing Method	Printing Resolution	Printed Structures	Dimension	Solidification	Mechanical Properties	Cell Density	Cell Viability	Ref
Bioprinted cells in 3D printed scaffolds
Cell-laden scaffold for CNS	PCL-PU hydrogel	NSC	Extrusion	~300-350 μm	Two layers lattice (grid) structure	20×20×10 mm3 (scaffolds)	Thermal responsive	Modulus 6-8 kPa	2×106 cells/ml	78%	[92]
Cell-laden scaffold	Alginate, chitosan, agarose	iPSCsa)	Extrusion	~200-300 μm	Multi-layers lattice	5×5 mm2 (scaffolds)	CaCl2 crosslinking	Indentation modulus < 5 kPa	4×107 cells/ml	Day 1:18% Day 9: 103%	[68]
Cell-laden scaffold	Alginate, chitosan, agarose	NSC	Extrusion	~200-300 μm	Multi-layers lattice	10×10×10 mm3 (scaffolds)	CaCl2 crosslinking	Compression modulus 7.5 kPa	5×106 cells/ml	Day 1:75% Day 6 :92%	[110]
Brain-like structure	Gellan gum-RGD	Primary cortical neurons	Manual extrusion (Hand-held printing)	Poor Resolution	Cylindrical consisted with six layers	~20 mm height and ~10 mm diameter (scaffolds)	CaCl2 crosslinking	-	1×106 cells/ml	78-80%	[111]
Artificial neural tissue	Cells in Collagen /VEGF in fibrin	Murine NSC (C17.2)+VEGF	Direct inkjet printing	Poor Resolution	Double layer with cells and VEGF	3×2 mm2 (scaffolds)	pH for collagen, thrombin for fibrin	-	1×106 cells/ml	~ 93%	[93]
3D scaffold for CNS	Cells in Matrigel printed on silicone scaffold	iPSC-derived progenitor cells	Extrusion	~150 μm	Microchannels	~150 μm width and 5 mm long (channels)	Temperature for Matrigel, moisture for silicone	Modulus ~ 10 MPa	1×107 cells/ml	> 75%	[15]
3D scaffold for CNS	Cells in Matrigel printed on alginate scaffold	iPSC-derived progenitor cells	Extrusion	~150 μm	Micro-channels	~150 μm width and 5 mm long (channels)	Temperature for Matrigel, CaCl2 crosslinking for alginate	Modulus 70-100 kPa	1×107 cells/ml	> 75%	[15]
3D scaffold for PNS	Fibrinogen, HA, PVA	Schwann cells	Extrusion	~200 μm	Micro-channels	~200 μm width and ~14 mm long (channels)	Thrombin	-	2×105 cells/ml	~ 98%	[112]
3D scaffold for PNS	Growth factors in GelMa on silicone scaffold	No cells, NGF for sensory path, GDNF for motor path	Extrusion	~250 μm	bifurcating nerves shape	~1 mm diameter and ~12 mm length (scaffolds)	UV crosslinking for GelMa, moisture for silicone	Young’s modulus 0.44 MPa	-	-	[17]
Seeded cells in 3D printed scaffolds
Lattice structure scaffold for CNS	GelMa-DAb)	NSCs	SLA	~200 μm	Multi-layers lattice	~10×10×0.8 mm3 (scaffolds)	UV crosslinking		3×104 cells/ scaffold		[113]
Lattice structure scaffold for CNS	GelMa/PEGDA	NSCs	SLA	~200 μm	Multi-layers lattice	~10×10×0.5 mm3 (scaffolds)	UV crosslinking	Compression modulus ~ 0.45 MPa	5×103 cells/scaffold	44.4%	[89]
Lattice structure scaffold with electrical stimulator for CNS	PEGDA for scaffold, MWCNT for stimulation	NSCs	SLA	~200 μm	Multi-layers lattice	~10×10×0.8 mm3 (scaffolds)	UV crosslinking	Young’s modulus 1.0 MPa	3×104 cells/scaffold		[106]
3D scaffold for CNS	GelMa/PEGDA	Neural progenitor cells	SLA	~200 μm	Micro-channels	~200 μm width and 2 mm long (channels)	UV crosslinking	Elastic modulus: 260-300 kPa	-	-	[34]
Tubular, multi-layer scaffold with electrical stimulator for PNS	PCL/graphene/RGD	Rat Schwann cell	3D printing and layer-by-layer casting	~50 μm	Multi-layer Tubular/microchannels	~15 mm long (scaffolds)	Solvent evaporation	Elastic modulus ~58.63-68.74 MPa	-	> 90%	[69]
3D scaffold for PNS	Collagen	Mesenchymal stem cells	Needle-array assembling (Kenzan Method)	~500 μm	For implantation, nerve protector (3-mm diameter) was used	~2 mm diameter and ~3.2 mm length (scaffolds)	Thermal responsive	-	6×105 cells/ml	-	[114]
3D scaffold for PNS	Silicone	Dorsal root ganglia /Schwann cells	Extrusion	~250 μm	Micro-channel	~1 mm diameter and ~12 mm length (scaffolds)	Moisture	Young’s modulus 0.44 MPa	6×104 cells/ml	-	[17]

^a)Induced Pluripotent Stem Cells (iPSCs);

^b)DA (Dopamine).