Table 1.

Summary of original studies performed in 2018–2020 on corneal bioprinting.

Corneal Layer	Bioprinting Method	Materials for Bioink	Cell Type	Cell Elongation	Mechanical Properties	Transparency Evaluation	Reference
Native cornea							[60]
Stroma			CSKs/LSSCs	Dendritic up to 100 µm	100–250 kPa	80% at 380 nm and
Epithelium			CEpCs/LECs	Round/polygonal tight monolayer	Fragile	>90% at 500–1300 nm
Endothelium			CECs	Hexagonal tight monolayer	Fragile
Stroma	Laser	Matrigel-COL I bioink // LN-COL IV support sheet	Human LECs+ ADSCs	Filopodial elongation up to 50 µm	n.a.	Qualitative: slightly opaque	[84]
	Extrusion	1.3% ALG-2.7% COL I bioink // FRESH support	Human CSKs	Round cells	n.a.	Qualitative: see through gel	[85]
	Drop-on-demand	0.2% COL I-0.5% AG bioink // no support	Human CSKs	Filopodial elongation up to 100 µm	15–20 kPa	Qualitative: see through gel	[86]
	Extrusion	15% GelMa bioink // reinforced with PEG-PCL fibers	Rat LSSCs	Filopodial elongation up to 50 µm	60–120 kPa	Qualitative: see through gel	[87]
	Extrusion	15% GelMa bioink // no support	Human CSKs	Round cells	10–20 kPa	Quantitative: 80% at 700 nm 5% at UVB	[88]
	Extrusion	Cornea-derived dECM bioink // no support	Human TDMSCs with keratocyte induction	Filopodial elongation up to 50 µm	70–100 kPa	Quantitative: 80% at 700 nm 70% at UVB	[89]
Epithelium	Extrusion	15% GelMa bioink // 15% GelMa dome-shaped mold	Human CEpCs line	Round cells	50 kPa	Qualitative: see through gel	[90]
Endothelium	Extrusion	Gelatin-RGD bioink // amniotic membrane dECM support	Human CECs	Round cells	n.a.	n.a.	[91]

Abbreviations: collagen (COL), laminin (LN), alginate (ALG), free-form reversible embedding of suspended hydrogels (FRESH), agarose (AG), methacrylated gelatin (GelMa), decellularized extracellular matrix (dECM), limbal epithelial cells (LECs), adipose-derived stem cells (ADSCs), corneal stromal keratocytes (CSKs), limbal stromal stem cells (LSSCs), turbinate-derived mesenchymal stem cells (TDMSCs), corneal epithelial cells (CEpCs), corneal endothelial cells (CECs).