Table 3.

Electrospun nanofiber scaffolds investigated for corneal tissue regeneration

Source	Materials	Fiber Diameter	Cell Type	Summary of Findings	Ref.
Natural	Collagen type I	30–50 nm	Rabbit corneal fibroblasts	In the aligned scaffold more than 50% downregulation of α-smooth muscle actin (α-SMA) was obtained compared to the unaligned scaffold and tissue culture plate. In addition, in case of aligned scaffolds, the rabbit corneal fibroblasts elongated along the fiber alignment, but no cell elongation was observed on unaligned fibers and tissue culture plate.	[124]
Natural	Collagen type I	137 ± 49 nm	Rabbit corneal fibroblast	Expression of α-smooth muscle actin (α-SMA) was significantly lower in aligned fiber scaffolds than unaligned scaffolds and tissue culture plate. In addition, in the aligned scaffold the light scattering was minimal that resulted in improved optical properties.	[146]
Hybrid	Polyvinyl acetate/ collagen type I	200–800 nm	Human corneal keratocytes (HKs) and human corneal epithelial cells (HCECs)	The mechanical properties, such as strength, stiffness, and elasticity, of the hybrid scaffolds was about 30x higher than the pure collagen scaffolds. Making aligned scaffolds further improved the mechanical and optical properties of the hybrid scaffolds 2 fold for HKs to grow orderly along the alignment.	[139]
Hybrid	PLGA/ collagen type I	500–2000 nm	HKs and HCECs	The tensile strength and light transmittance of the hybrid scaffolds were 3.41 MPa and 63%, respectively. The HKs maintained their natural phenotype and the HCECs formed multilayered epithelium similar to the natural epithelium when cultured for 2 weeks.	[125]
Hybrid	Collagen type I /Chondroitin Sulfate (crosslinked via carbodiimide cross-linker)	Collagen: 400–500 nm Hybrid: 300–400 nm	HCECs	The tensile strength of the crosslinked nanoscaffolds was about 4x higher than the non-crosslinked nanoscaffolds and the crosslinking decreased scaffold degradation by 70%−80%. However, the viability of HCECs was 40–50% lower in the cross-linked nanoscaffolds than in the non-cross-linked nanoscaffolds.	[126]
Hybrid	PCL-PGS and PCL-chitosan	PCL-PGS: 300–500 nm; PCL-chitosan: 100–200 nm	HKs and HCECs	Elongated HKs and HCECs grew on the aligned fibers, which had a nearly 100% light transmittance. But the HCECs metabolic activity was about 40% higher in the PCL-PGS nanoscaffolds than the PCL- chitosan nanoscaffolds.	[130]
Hybrid	PCL-PGS	150–500 nm	Human corneal endothelial cells and Human conjunctival epithelial cells	In a wet state, the aligned scaffolds had nearly 100% light transmittance. In addition, in scaffolds with higher PGS content, delayed but normal cell growth, higher cell orientation (~50%) and natural HCEC morphology were obtained.	[127]
Synthetic	PLA	Aligned: 696 nm	Bovine corneal keratocytes	The PLA scaffolds supported the growth of the cells and maintained the cell morphology. They had slower degradation rate, but only 80% light transmittance, compared with collagen scaffolds.	[144]
Synthetic	PCL	100 nm	Human corneal epithelial stem cells	Similar viability of the stem cells grown in the PCL nanofibrous scaffolds and a human amniotic membrane (clinically standard substrate for corneal surface repair) was obtained over 15 days, with no sign of differentiation.	[140]
Hybrid	Silk fibroin -poly(L-lactic acid-co-ε-caprolactone SF:P(LLA-CL)	100–650 nm	HCECs	Formation of monolayer cells with expression of tight junction protein ZO-1 and functional genes (e.g. Na+K+-ATPase, solute carrier family-4 member-4 (SLC4A4), voltage-dependent anion channel 3, voltage-sensitive 3 chloride channel, aquaporin-1), was observed.	[145]
Hybrid	PCL-Keratin (50:50)	144 nm	Human mesenchymal stem cell (hMSCs)	Addition of keratin into PCL nanoscaffolds improved cell adhesion by 20%, aided cytoplasmic extension and resulted in elongated morphology. The hybrid nanoscaffolds made the cells to grow longer than 7 days, which could not be achieved by the PCL nanoscaffolds.	[134]
Hybrid	PLGA (50:50)/Collagen Type I; 3-layered nanoscaffolds (PLGA-Collagen-PLGA) were crosslinked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) or glutaraldehyde.	Aligned: 200–300 nm Unaligned:500–1000 nm	Human endometrial stem cells	Both crosslinked scaffolds had improved physical and mechanical properties, wettability, and cell viability. However, the EDC crosslinked nanoscaffolds exhibited around 52%, 127%, 1.3%, and 23% higher Young’s modulus, tensile strength, strain% at break, and cell viability, respectively, and around 5% lower degradation after 84 days than the glutaraldehyde crosslinked nanoscaffolds.	[158]