## 3 Tissue Engineering Approach
### Conventional Fabrication Techniques  
Solvent casting techniques have been highly utilized in ocular tissue engineering [45]. They consist of dissolving a polymer in an appropriate solvent followed by casting and solvent evaporation [46]. The resulting scaffold is a uniform and non-porous film. In retinal tissue engineering, these films were seeded with RPE cells to regenerate the RPE layer and replace Bruch's membrane for AMD treatment, thus preventing the loss of photorecep  
Figure 2: Overview of fabrication methods used for retinal tissue engineering. SC/PL stands for solvent casting-particulate leaching and TIPS for thermally induced phase separation. The red arrow indicates the increase in precision and resolution of the techniques. tors [47; 48; 49; 50; 51]. The prosthetic Bruch's membrane manufactured by solvent casting displayed a similar thickness to the human Bruch's membrane and promoted correct implantation and orientation of the cellular graft in the subretinal space. Moreover, as the degradation of the polymer proceeds, transplanted RPE cells should re-establish interactions with the native Bruch's membrane [47]. To enhance the survival of a functional RPE monolayer in the long term, the film surface was modified [52; 53]. [PERSON] et al. showed that silk fibroin scaffolds coated with type I collagen promoted the in vitro development and survival of a functional RPE monolayer for 90 days [52]. [PERSON] et al. used oxygen plasma treatment to render a film surface hydrophilic, thus enhancing cell attachment and spreading [53]. However, the film's non-porous structure did not match the open fibrillar structure of the native [PERSON]'s membrane and could prevent nutrient diffusion from the choroid in vivo. To generate a porous scaffold, a solvent casting/particle leaching (SC/PL) method was adopted in biomedical applications [54]. In the SC/PL technique, the solvent, where the polymer is dissolved, contains leachable particles known as porogen [55]. This method allows the production of scaffolds with high porosity (up to 93%) in a simple, inexpensive way [54]. Prosthetic Bruch's membranes for RPE transplantation were successfully prepared using the SC/PL method [56; 57; 58]. Moreover, to develop an optimized cell therapy strategy, the influence of the scaffold pore size on the cell differentiation into the retinal precursor has been investigated [59]. However, the low reproducibility limits the use of the SC/PL technique for retinal tissue engineering applications [60]. Over the last decade, hydrogels have received considerable attention as leading candidates for engineering soft tissues such as the retina due to their unique compositional and structural similarities to the ECM [61]. As such, they are highly hydrophilic and biocompatible, thus promoting cell attachment, proliferation and differentiation. Various methods have been used to produce hydrogels depending on the desired structure and application [61]. The most common method of hydrogel preparation involves the crosslinking of the polymer solution poured into a mold of a specific shape. Crosslinking may occur by physical or chemical methods; the type and degree of crosslinking strongly affects the properties of hydrogels such as the elastic modulus, nutrient transport and swelling capacity [62]. In retina tissue engineering, hydrogels have been employed as scaffolds for RPE, photoreceptors and the regeneration of RGCs [63; 64; 65; 66; 67; 68; 69; 70]. For instance, implantable hydrogels with encapsulated cells were proposed as promising candidates to treat those blinding diseases caused by the degeneration of the RPE. Hydrogels acted as a cell delivery vehicle providing an appropriate environment for RPE regeneration [63; 64; 65]. [PERSON] et al. seeded an induced pluripotent stem cell (iPSC)-derived RPE onto the surface of thin fibrin hydrogels as a support material for RPE transplantation [66].