**Abstract**

Nanowires aim at developing advanced architectures are gaining popularity for damaged neural systems. The retina with a complicated structure is an essential part of our visual nervous system. Any disorder inside retina could lead to blindness due to irregularity in transferring neural signals to the brain. In recent years, the emergence of nanostructures, as well as nanowires, has provided a viable means for enhancing the regeneration of retinal. Nanowires with the ability to sense light and converting it to the electrical signals simulate the extracellular electrical properties, which are the newest nanostructures for the retinal applications. The different structure of nanowires has been examined in vitro, and several others are undergoing in vivo for vision recovery. Among the structures, core-shell nanowires and functionalized nanowires with gold nanoparticles attract the attention for the regeneration of retinal neural systems. Herein, subsequently provide an introduction to the anatomy of the retina, and retinal disorders, the latest progress in the regeneration of retina and vision using nanowires will be reviewed. Also, the different structures, including core-shell and functionalized nanowires with nanoparticles, will be examined. Eventually, the point of view and perspective of applying nanowire in retinal regeneration will be offered.

**Keywords:** regeneration of retina, nanowires in ophthalmology, nanowires for tissue engineering, nanowires biocompatibility

#### **1. Introduction**

The retinal transplantation is limited due to the complex neural network [1]. Retina senses light and converts it into the neural signals and transfers neural signals to the brain and cause visual perception [2, 3]. Nanostructures have evolved as multidisciplinary applications by combination with materials as an advanced architecture to develop functional substitutes for various proposes such as wound dressing [4–6], tissue engineering [7–11], and biomedical applications [12–14]. Neuroscience, related to the retina is one of the most exciting fields where nanostructures with modified properties serve as scaffolds to promote and facilitate the migration and adhesion of the cells [15].

Until recently, it was believed that scaffolds simulated the extracellular matrix (EMC) in the regeneration of retina, and served as a support for cell migration, adhesion, and morphology only [16–18]. Emphasis was on loaded materials and morphology construction to develop biocompatible and biodegradable scaffolds

with appropriate mechanical properties [19–22]. However, the first definition of tissue regeneration is developing scaffolds with acceptable biocompatibility to implant in the host body to repair damaged tissues or organs. Therefore, the electrospun nanofibers with a high ratio of surface-to-volume, tunable porosity, and similarity to natural EMC show the ability to modify the surface functions with different structures for a wide range of tissue regeneration [23]. Nanofibers have emerged as a potential to simulate the ECM in many tissues such as bone [10], nerves [24], and various techniques have been employed to fabricate the nanofibers with excellent properties [25].

metabolic products from the subretinal space to the blood and receiving nutrients such as glucose and retinol from the blood to nourish the photoreceptors playing the critical role in the retina layer. However, failure in mentioned functions can lead to

PL is the only light-sensitive part of the neuroretina and is composed of outer and inner segments of the rod and cone cells. Cone cells are responsible for color detection and are found in high number in the macula, especially foveal region, whereas rods are more active in the dark and are abundant in the peripheral retina. OLM layer separates PL from the photoreceptor nuclei, and it is not considered as an actual layer. ONL contains the nuclei of photoreceptors, and its thickness varies across the retina with the maximum thickness at the fovea. However, the axons of the photoreceptors cells and their synapses with bipolar and horizontal cells form the OPL. On the other hand, cell bodies of horizontal cells, bipolar cells, amacrine cells, and Muller glial cells are in the INL layer. The INL layer, playing the critical role to transmit inputs signals from IPL to OPL, which is composed of synapses between the bipolar, ganglion, and amacrine cells. The innermost layer of the retina is GCL and located in the place near to the vitreous and contains the cell bodies of ganglion cells and displaced amacrine cells, astrocytes, and Muller cell bodies that their axons converge on the way to the optic disc and form NFL. The latest layer of the retina is ILM, which forms the inner boundary of the retina on the vitreous side. **Figure 1** is showing the retinal layer that divided into nine layers with nine different

The macula is a region inside the retina which contains the highest number of ganglion cells and cause the optimal vision and color perception process [44]. Rods and cones are responsible for the initiation of the scotopic and photopic visual processing, respectively. When the light absorbed by photoreceptors, rod, and cone cells with releasing glutamate as a neurotransmitter cause to transfer the electrical signals from synapse onto the bipolar cells at the OPL layer. Afterward, transferring

*The anatomy of retina from outer layer (up) to inner layer (down) is containing of retinal pigment epithelium (RPE), outer segment of photoreceptors (OS), outer nuclear layer (ONL), outer plexiform layer (OPL), inner nuclear layer [41], inner plexiform layer (IPL), ganglion cell layer (GCL), inner segments of photoreceptors (IPL), optic fiber layer (OFL), and inner limiting membrane (ILM) from nearest to choroid to nearest to vitreous, respectively. The retina is consist of nine cell line consisting of rod photoreceptor (R), cone photoreceptors (C), horizontal cells (HC), bipolar cells (BC), amacrine cells (AC), displaced amacrine cells*

*(dAC), retinal ganglion cells (RGC), Muller cells, and astrocyte cells (Astro) [2].*

retinal degeneration, visual loss, and eventually blindness [43].

*Application of Nanowires for Retinal Regeneration DOI: http://dx.doi.org/10.5772/intechopen.90149*

cell type [40].

**Figure 1.**

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As extracellular electrical simulation involves in neuroscience and neural tissue engineering [26–28], attention is focused on nanowires applications for visual neural system [29–31], brain [32, 33] and cardiac [34]. Nanowires have recognized as widely used nanostructure for the cell microenvironment where the electrodynamic properties [35] have permanently affected cellular functions, such as morphology, adhesion, differentiation, and proliferation [36]. As a consequence, researchers have developed new structures for better electroconductivity, biocompatibility, and cell adhesion [37–39].

Nanowires have been shown that simulate the nerve signals in the retina and transfer between the layers could improve the vision loss by the damaged retina. To explain the recovery of vision with nanowires, which lost by retinal degeneration, we will begin by describing the retinal anatomy, and how various retinal disorders may cause blindness. Then we will investigate the nanowires which could enhance retinal organization with sensing light and converting it to the electrochemical signals with different materials, structures, and properties. Finally, we will discuss the challenges ahead and prospect in the application of nanowires for recovery of vision that lost by retinal destruction.
