## 3 Tissue Engineering Approach
### Electrosppinning
Electrospun scaffolds have been employed also in neural retina engineering to guide the growth of RGC axons through the control of fiber orientation [101; 102; 103]. This approach could benefit patients suffering from glaucoma and optic nerve diseases. The transplantation of functional RGCs onto a suitable support combined with treatments that promote dendritic integration may regenerate axons and help recreate a healthy axonal transport. Radially oriented scaffolds have been investigated for the transplantation of RGCs as they mimic the radial axon pattern [101]. It was observed that radially oriented scaffolds increased the survival of RGCs while preserving the cellular electrophysiological function. Moreover, these scaffolds promoted RGC axonal integration with the host retinal nerve fibers in retinal rat explants whereas RGCs transplanted directly onto explants grew axons in a randompattern [101]. [PERSON] et al. compared radially and randomly oriented scaffolds to regenerate photoreceptors. They found that the expression of rod photoreceptor-specific genes increased when stem cells were differentiated on randomly oriented nanofibers [104]. Electrospun scaffolds for retina applications are summarized in Table 2.  
Despite the advantages, the electrospinning technique has a limited microarchitecture controllability. Therefore, to overcome this drawback, melt electrowriting (MEW) has been recently developed [105]. MEW allows the controlled deposition of a polymer melt fiber starting from a digital model, thus combining melt electrospinningning and additive manufacturing principles. To the best of our knowledge, this innovative method has been used in vascular, bone and skin tissue engineering but no studies on a retinal application are yet present [106; 107; 108]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Fabrication Technique** & **Scaffold Structure** & **Cell Type** & **Research Stage** & **Reference** \\ \hline Electrospinning & Ultrathin random nanofibrons & Human RPE cells & In vitro & [85] \\ Electrospinning & Ultrathin random nanofibrons & Human RPE cells & In vitro and & [86] \\ Electrospinning & membrane & Human RPE cells & in vivo (rabbit) & [86] \\ Electrospinning & Random nanofibrons & Rat retinal progenitor cells & In vitro & [87] \\ Electrospinning & Random nanofibrons & Porcine RPE cells & In vitro and & [88] \\ Electrospinning & membrane & Human RPE cells & In vitro and & [89] \\ Electrospinning & Random nanofibrons & Human fetal and adult & In vitro & [90] \\ Electrospinning & membrane & RPE cells & In vitro & [91] \\ Electrospinning & Random nanofibrons & Human RPE cells & In vitro and & [92] \\ Electrospinning & Random nanofibrons & Human fetal RPE cells & In vitro and & [93] \\ Electrospinning & Random nanofibrons & Human RPE cells & In vitro & [94] \\ Electrospinning & membrane & Human iPSC-RPE cells & In vitro and & [95] \\ Electrospinning & Nanofibrous membrane & Human ESC-RPE/bovine & In vitro & [96] \\ Electrospinning & Random nanofibrons & RPE cells & In vitro & [97] \\ Electrospinning & membrane & Human RPE cells & In vitro and & [98] \\ Electrospinning & Random nanofibrons & Human cell line & In vitro and & [99] \\ Electrospinning & membrane & ARPE-19/MIO-M1 & in vivo (rat) & [98] \\ Electrospinning & Random nanofibrons & Rat retinal progenitor cells & In vitro & [99] \\ Electrospinning & Random nanofibrons & Human cell line ARPE-19 & In vitro & [100] \\ Electrospinning & Alphed nanofibrons & Rat RGCs & In vitro and & [101] \\ Electrospinning & Alphed nanofibrons & Rat RGCs & In vitro & [102] \\ Electrospinning & membrane & Rat RGCs & In vitro and & [103] \\ Electrospinning & Random nanofibrons & Human iPSC-RGCs & (rabbit/monkey) & \\ Electrospinning & Random + aligned nanofibrons & Human conjunctiv stem & & [104] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: A summary of retinal scaffolds fabricated by electrospinningning. This table highlights the fabrication technique, the structure of the scaffold and the cell type used.