Table 3.

Summary of current advances in natural scaffold and film engineering for corneal tissue.

Materials	Novelty	Research Model			Ref
		Material Characterization	In Vitro Cell Studies	In Vivo or Ex Vivo Studies
Epithelium
Silk fibroin	Optimization of silk fibroin, poly-D-lysine coated silk fibroin, RGD modified silk fibroin, and poly-D-lysine blended silk fibroin films for human corneal epithelium growth	–Spectroscopy	–Human CEpCs	--	[102]
Silk fibroin	Silk films with nanotopography and extracellular proteins	–Morphology	–Murine CEpCs –Rabbit CEpCs	–Corneal epithelium debridement in C57BL/6 mice	[89]
Silk fibroin	Silk film with tunable stiffness and cellular effects	–Mechanical properties –Morphology	–Human CEpCs	--	[82]
Silk fibroin	Various silk film surface features of various pitch and width dimensions ranging from the micro- to nanoscale	–Morphology	–Human CEpCs	--	[103]
Silk fibroin	Hybrid silk/PU electrospun mat for corneal epithelial differentiation of conjunctiva-derived MSC	–Mechanical properties –Morphology	–Human MSCs	--	[84]
Silk fibroin	Fabrication and biocompatibility of electroconductive silk/PEDOT/PSS composites	–Degradation –Mechanical properties –Spectroscopy –Transparency	–Human CEpCs	--	[90]
Silk fibroin	PEG modified silk membranes as a carrier for limbal epithelial stem cells transplantation	–Morphology	–Rabbit LESCs	–Limbal stem cell deficiency NZW rabbit model	[91]
Collagen	Collagen/chondroitin sulfate film with high moisture capacity	–Mechanical properties –Spectroscopy –Transparency	–Human CEpCs	--	[104]
Collagen	Collagen film with micro-rough surface	–Morphology	--	–Lamellar keratoplasty in NZW rabbits	[105]
Chitosan/gelatin/HA	Carboxymethyl chitosan/gelatin/HA membrane as transplantation scaffold for corneal wound healing	–Transparency	–Rabbit CEpCs –Rabbit CSCs	–Alkali burn-injury in NZW rabbits	[106]
Stroma
Silk fibroin	Contact guidance by RGD-treated silk films stacked in an orthogonally, multi-layered architecture to control the alignment and distribution of human LSSCs	–Mechanical properties –Morphology –Spectroscopy –Transparency	–Human LSSCs –Human CFs	--	[92]
Silk fibroin	Investigate the in vivo response and the effect of silk crystalline structure on degradation rates of silk films in rabbit multipocket corneal models	–Spectroscopy	--	–Corneal multipocket model in NZW rabbits	[93]
Silk fibroin	Silk film using centrifugal casting technique for corneal tissue engineering	–Mechanical properties –Morphology –Transparency	–Human CKs	--	[83]
Silk fibroin	Influence of surface topography and mechanical strain on keratocyte phenotype and ECM formation	–Morphology –Transparency	–Human CKs	--	[94]
Silk fibroin	Multi-lamellar human corneal stroma tissue in vitro by differentiating periodontal ligament stem cells towards keratocytes on an aligned silk membrane	–Morphology	–Human periodontal ligament stem cells	--	[95]
Silk fibroin	Corneal stromal regeneration by hybrid silk/PCL electrospun scaffold	–Degradation –Mechanical properties –Morphology –Spectroscopy –Transparency	–Human CKs	--	[85]
Silk/ GelMA	Transparent hybrid silk/GelMA films for cornea tissue engineering	–Degradation –Mechanical properties –Morphology –Spectroscopy –Transparency	–Human CFs	--	[87]
Silk/ GelMA	Double-layer film with ascorbic acid reservoir sodium alginate adhesive and anisotropic layer of micro-patterned silk nanofibrils incorporated with gelatin methacrylate for stroma tissue engineering	–Degradation –Mechanical properties –Morphology –Spectroscopy –Transparency	–Human CSCs	--	[86]
Collagen	Examine the influence of compositional and structural differences on keratocyte behavior	–Degradation –Morphology –Transparency	–Bovine CKs	--	[107]
Collagen	Pure collagen-based biomimetic 3D corneal stromal model constructed from pure electro-compacted collagen	–Degradation –Mechanical Properties –Morphology –Transparency	–Human CSCs	--	[108]
Decellularized bovine corneal matrix	Examine the influence of compositional and structural differences on keratocyte behavior	–Degradation –Morphology –Transparency	–Bovine CKs	--	[107]
Decellularized human stromal refractive lenticules	Femtosecond laser-derived human stromal lenticules decellularized with sodium dodecyl sulfate could produce transplantable biomaterial	–Morphology –Transparency	–Human CFs	–SMILE surgery in NZW rabbits	[109]
Endothelium
Silk fibroin	Silk-based artificial endothelial graft for use in a rabbit Descemet’s membrane endothelial keratoplasty	–Mechanical Properties –Transparency	–Human CEnCs –Rabbit CEnCs	–Descemet membrane endothelial keratoplasty surgery in NZW rabbits	[96]
Silk fibroin	Transparent ultrathin film scaffolds with nature-derived aloe vera gel and silk	–Morphology –Spectroscopy –Transparency	–Rabbit CEnCs	–Descemet’s stripping and endothelial keratoplasty in NZW rabbits	[97]
Silk fibroin	Silk/β-Carotene films for delivery of corneal endothelial cells to replace diseased corneal endothelial cells	–Morphology –Spectroscopy –Transparency	–Rabbit CEnCs	--	[98]
Silk fibroin	Silk/lysophosphatidic acid films as a substrate for corneal endothelial cell delivery	–Morphology –Spectroscopy	–Rabbit CEnCs	--	[99]
Silk fibroin	Transparent silk/glycerol film, as a potential substrate for corneal endothelial cell regeneration	–Morphology –Spectroscopy –Transparency	–Rabbit CEnCs	--	[100]
Philosamia ricini silk	Non-mulberry silk for the culture of corneal endothelium	–Degradation –Mechanical properties –Morphology –Spectroscopy –Transparency	–Human CEnCs	--	[101]
Antheraea assamensis silk	Non-mulberry silk for the culture of corneal endothelium	–Degradation –Mechanical properties –Morphology –Spectroscopy –Transparency	–Human CEnCs	--	[101]
Collagen	Collagen/PLGA as a substrate for corneal endothelial cell regeneration	–Degradation –Morphology –Transparency	–Rabbit CEnCs	--	[110]
Full Thickness
Silk fibroin	Thin silk protein film stacks as the scaffolding to support the corneal epithelial and stromal layers, and a surrounding silk porous sponge to support neuronal growth	--	–Human LSSC –Human CEpCs –Chicken dorsal root ganglion cells	--	[111]
Silk fibroin	Combining the corneal stroma and epithelium into one co-culture system, to monitor both human LSSC and human CEpC growth and differentiation into keratocytes and differentiated epithelium	--	–Human LSSCs –Human CEpCs	--	[112]
Silk fibroin	Biodegradable silk fibroin-based scaffolds containing glial cell line-derived neurotrophic factor for re-epithelialization	–Degradation –Mechanical properties –Morphology	–Human CKs	–Epithelial-stromal damage in C57BL/6 J mice	[88]
Collagen	Microgroove films as an external cue for cell responses	–Degradation –Transparency	–Rabbit CEpCs –Rabbit CKs	--	[113]
Collagen	Incorporation of cellulose nanocrystals into collagen films for improved mechanical properties	–Degradation –Mechanical properties –Morphology –Transparency	–Rabbit CEpCs –Rabbit CKs	--	[114]
Collagen	Collagen/PVAc nanofibrous electrospun scaffold suitable for cornea tissue engineering	–Mechanical properties –Morphology –Transparency	–Human CKs –Human CEpCs	--	[115]
Collagen	3D hemispherical transparent scaffold with radially aligned nanofibers fabricated with the designed peg-top collector	–Mechanical properties –Morphology –Spectroscopy –Transparency	–Rabbit corneal cells	--	[116]
Decellularized porcine cornea	Construct a full-thickness artificial cornea substitute in vitro by coculturing limbal epithelial cell-like cells and corneal endothelial cell-like cells derived from human embryonic stem cells on scaffolds	–Mechanical properties –Transparency	–Human CEpCs –Human CFs –Human embryonic stem cells	–Penetrating keratoplasty in NZW rabbits	[117]
Decellularized porcine cornea	Method using supercritical carbon dioxide to prepare acellular porcine cornea	–Mechanical properties –Morphology	--	–Anterior lamellar keratoplasty in NZW rabbits	[118]
Decellularized porcine corneal scaffolds	Decellularized corneas by formic acid, acetic acid, and citric acid treatment for corneal regeneration	–Mechanical properties –Transparency	–Human CEpCs –Rabbit CKs	–Deep anterior lamellar keratoplasty in NZW rabbits	[119]