Table 1. A summary of biomaterials used for retinal tissue engineering.

PLGA: poly(lactic-co-glycolide acid), PLLA: poly(l-lactic acid), PGS: poly(glycerol-sebacate), PTMC: Poly (trimethylene carbonate), PCL: polycaprolactone, PMMA: poly(methyl methacrylate), SF: silk fibroin, PDLJA: poly (D, L-lactide), PLCL: poly(L-lactic acid-co-ε-caprolactone, hESC: human embryonic stem cell, RPE: retinal pigment epithelium, RCS: royal college of surgeons, BM: Bruch’s membrane, BMSF: bombyx mori silk fibroin, RPC: retinal progenitor cells, AMD: advanced macular degeneration, PNIPAAm: poly(N-isoproplyacrylamide).

Biomaterial	Thickness (μm)	Advantages	Studies	References
Collagen type I membrane	7	Non-toxic, no inflammatory response, controllable, stability (10 weeks), degrade (within 24 weeks)	Long term biocompatibility and membrane degradation evaluated (rabbits)	(Bhatt et al., 1994; Booij et al., 2010; Lu et al., 2007; Thumann et al., 2009)
Gelatin	30–35	Lower immunogenicity, crosslinking ability, and better solubility in aqueous systems	Biocompatibility, improved survival, and formation of laminar structures (rabbits)	(Hsiue et al., 2002; Lai and Li, 2010)
Alginate	Thin film	Purified alginate- high cell proliferative rate	Ability to support the growth of RPE cells and their high proliferative rates (in vitro)	(Heidari et al., 2015; Hunt et al., 2017; Jeong et al., 2011)
Silk Fibroin	3	Great mechanical strength, good biodegradability, and biocompatibility	Evaluate BMSF as a substrate for RPE cell transplantation (in vitro)	(Shadforth et al., 2012; Tran et al., 2018)
PLGA		Remarkable mechanical properties, adjustable degradation rates (80–90 days), and good processability	To demonstrate safety and cell integration in the eye (rodent and porcine preclinical models)	(Pan and Ding, 2012; Sharma et al., 2019)
PCL	20–40	Thinnest scaffold, permeable, slow degradation, adverse tissue responses not observed	Assess the tolerance and durability of micro and nanostructured PCL thin films (rabbits)	(Bernards et al., 2013; Redenti et al., 2008)
PTMC	100	Elastomeric properties similar to BM, thickness tunable	Demonstrate adherence and maturation of hESC-RPE cells on PTMC compared to PDLLA films	(Sorkio et al., 2017)
PMMA	6	Reduced risk of trauma	Evaluate adhesion of RPCs and its differentiation and migration to host retina (mice)	(Tao et al., 2007)
PGS	45	A suitable candidate for RPC delivery with great novel properties	Evaluate mechanical properties	(Neeley et al., 2008)
Parylene-C	0.15–0.30, 0.3 μm thickness supported on a 6.0 μm thick mesh frame	Macromolecules and nutrients can diffuse, nonimmunogenic, Promotes cell adhesion after vitronectin/matrigel coating	Evaluate safety, survival, and functionality of hESC-RPE cells on parylene in animal models	(Kashani et al., 2018; Koss et al., 2016; Lu et al., 2012; Thomas et al., 2016)
	0.3 μm thickness supported on a 6.0 μm thick mesh frame		Assess safety and efficacy of hESC-RPE on parylene in patients with AMD. (clinical study)
			Check cell adherence and proliferation (in vitro)
PLLA & PLGA	Week 1: 133.1 Week 2: 131.5 Week 3: 103.5	25:75 (PLLA: PLGA) thinnest, most porous, and minimal cell death	Evaluate the variety of suitable scaffolds for RPE transplantation (in vitro)	(Thomson et al., 2011)
SF & PLCL	60–100	Quick RPC proliferation, preferential differentiation towards retinal neurons like photoreceptors	Understand effects of blended nanofibrous membranes of silk fibroin and PLCL (in vitro)	(Zhang et al., 2015)
Honeycomb like films and collagen IV		Increased hydrophilicity, high permeability	Investigate honeycomb-like film as a promising scaffold for hESC-RPE tissue engineering	(Calejo et al., 2016)
PNIPAAm - Thermoresponsive polymer	scalable	Allows cell sheet harvest by temperature reduction from 37–20 °C	Demonstrate fabrication of transplantable retinal pigment epithelium cell sheets	(Kubota et al., 2006; Kushida et al., 1999)
Decellularized matrix	10–20	micro- and macro-scale structural components and functional ECM proteins present Photoreceptor differentiation	Develop novel biomaterial by decellularizing retina using ionic detergents	(Kundu et al., 2016)