**4.1 Extracellular matrix simulation and cell adhesion**

Tissue engineering specified as two foremost policies to redevelop the injured tissues or organs such as (1) cell-based; when cells are the critical substance to modify the place before transplanted to the host body, and (2) scaffold-based; when an extracellular matrix (ECM) from biomaterials designed and simulate in vivo structures. Recreating the retina requires effective architecture to mimic the extracellular matrix with physiological and morphological features resembling the in vivo structure [70]. The ECM with the composition of an intricate interweaving of protein provides the appropriate structure for cells grow with vast morphogenesis, which creates the vary forms of tissue and organs. However, the ECM classified into the two main categories of interstitial and pericellular. The interstitial matrices define as matrices that surround cells, whereas; pericellular matrices are with close contact with cells. The obvious example is the basement membrane, which is a type of pericellular matrix, and with providing an anchoring, membrane prevents parenchymal cells to break apart [71]. Also, unique ECM is associate to differentiate, changes in morphology and topography of cells to form the unique tissue and organs [72].

The mature mammalian retina is consists of two basement layer such as Brunch membrane at the interface between retinal pigment epithelium (RPE) membrane and choroid and second is the inner limiting membrane (ILM) at the interface of the neural retina with the vitreous body [73]. **Figure 2** is showing the two basement layers in the structure of the retina and their morphogenesis.

#### **Figure 2.**

*Immunohistochemistry of the 8 weeks gestation human that stained with the immunofluorescent antibody. The yellow line labeled are showing the Bruch's and ILM membrane that continues the same identical membrane folded over inside the eye (A), the scanning electron microscope of the ILM membrane showing that the surface in contact with RPE (Ret) is irregular whereas the vitread surface (Vit) represents the smooth surface (B), and Bruch's membrane showing the composition of aligned collagenous fibers (F) in composition of cell process (C) [74, 75].*

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

made from *n-type* and *p-type* silicon for making connections between the membranes of live bipolar cells and nanowires to sense the light for the recovery of vision [69]. **Table 1** represents the materials have been used as nanowires for vision

Tissue engineering specified as two foremost policies to redevelop the injured tissues or organs such as (1) cell-based; when cells are the critical substance to modify the place before transplanted to the host body, and (2) scaffold-based; when an extracellular matrix (ECM) from biomaterials designed and simulate in vivo structures. Recreating the retina requires effective architecture to mimic the extracellular matrix with physiological and morphological features resembling the in vivo structure [70]. The ECM with the composition of an intricate interweaving of protein provides the appropriate structure for cells grow with vast morphogenesis, which creates the vary forms of tissue and organs. However, the ECM classified into the two main categories of interstitial and pericellular. The interstitial matrices define as matrices that surround cells, whereas; pericellular matrices are with close contact with cells. The obvious example is the basement membrane, which is a type of pericellular matrix, and with providing an anchoring, membrane prevents parenchymal cells to break apart [71]. Also, unique ECM is associate to differentiate, changes in morphology and topography of cells to form the unique tissue and

The mature mammalian retina is consists of two basement layer such as Brunch membrane at the interface between retinal pigment epithelium (RPE) membrane and choroid and second is the inner limiting membrane (ILM) at the interface of the neural retina with the vitreous body [73]. **Figure 2** is showing the two basement

*Immunohistochemistry of the 8 weeks gestation human that stained with the immunofluorescent antibody. The yellow line labeled are showing the Bruch's and ILM membrane that continues the same identical membrane folded over inside the eye (A), the scanning electron microscope of the ILM membrane showing that the surface in contact with RPE (Ret) is irregular whereas the vitread surface (Vit) represents the smooth surface (B), and Bruch's membrane showing the composition of aligned collagenous fibers (F) in composition of cell process (C)*

**4. Nanowire based mechanism of retina regeneration**

layers in the structure of the retina and their morphogenesis.

**4.1 Extracellular matrix simulation and cell adhesion**

recovery lost due to retinal disorders.

*Regenerative Medicine*

organs [72].

**Figure 2.**

*[74, 75].*

**124**

Recently, Kharaghani and co-workers [76] reported a study emphasizing the importance of morphogenesis in the three-dimension (3D) nanofibers scaffold structure in guiding the seeded cells for ophthalmic tissue engineering mainly for cornea and retinal applications. The necessities for using scaffolds in ophthalmic tissue engineering are cell adhesion besides to tensile strength, effectiveness on cell morphology, and topography of scaffolds [76]. This report stressed the significance of the underlying ECM in endorsing exclusive micro and nanoenvironments that fosters tissue regeneration. However, it is unfortunate that there is no report about the study of ECM simulation by nanowires or surface chemistry of nanowires that shows cell adhesion, where it is used for retinal regeneration. At the moment, all reports have been used the single nanowire for the regeneration of retina.

In attempts to control the cell adhesion on nanowires, researchers repopulated their strategy to change the surface chemistry nanowires prepared based on titanium, silicon, and zinc [77–79]. However, the in vitro and in vivo researches have been don around the regeneration of retina by nanowires, and results show that cells tended to encompass. Also, it should be happening due to electrical stimulation of place based on the extracellular electrical.

#### **4.2 Extracellular electrical simulation**

It is mentioned here earlier that converts light into the neural signals and transfer neural signals to the brain by retina will lead to visual perception. Extracellular electrical involving ion channels has a vital role in nervous systems such as the retina. Photovoltaic polymers such as silk have been shown the great potential to use a connection between the layer of the retina to restore the vision with transfer the electrical signals [80]. The intracellular voltage is one of the unknown metrics that many types of research have been focused on recording signal strength use a nanoscale electrode as well as nanowires. Nanowires have been shown the tremendous potential upon extracellular electrical stimulation of cells to promote cell growth, adhesion, and differentiation. Also, Vodovnik and coworkers showed that the external electrical field had a significant effect on the polarization of cells on the cathodal and anodal side of the electrode [81].

On the other hand, the positive and negative charge should be optimized for the clinical implant to achieve successful results. The cationic polymers and nanoparticles with high concentrations of nitrogen may help to compaction of negative charge DNA and RNA and lead to better gens protection and endosomal escape in addition to high transaction efficiency and stability [2]. **Figure 3** is showing how nanowires with simulating the extracellular electric could cause cell adhesion to the nanowires and effect on the recovery of vision after implantation in mice eye.

Among the various nanostructures, gold nanoparticles due to high electroconductivity, biocompatibility, and chemical inertness have been attracting the attention to develop scaffolds for neural systems such as retinal applications. However, it is unfortunate that the development of high-quality gold nanowires faces challenges in the absence of robust methods for synthesis. Nevertheless, the gold nanoparticle with the electrical resistance of 52 Ω is one of inseparable part of scaffolds have been used for retinal applications as reported in **Table 1**, which gold nanoparticles have embedded with nanowire structures [61].

In an attempt to design an implantable electronic device for regeneration of retina when photoreceptors are damaged, electrically stimulate of retinal neurons, become an essential challenge. Whereas, several retinal prostheses are going on, but none of them have shown the ability to evoke phosphenes in blindness. Refer to retinal anatomy controlling the signal impedance is the most crucial subject to

#### **Figure 3.**

*The immunohistochemical graph of glial cells from mouse have been cultured on gallium nanowires, the cells stained green by glial fibrillary acidic protein (GFAP) and cells nuclei stained blue by 4,6-diamidino-2 phenylindole (DAPI) (A), SEM image from rat dorsal root ganglion cell surrounded a single a coaxial* ntype*/*p-type *silicon nanowire (B), SEM image from interface between the mice retina (RPE) and titanium dioxide array nanowire modified by gold nanoparticles (C), and the response of UV-light-evoked in the blind mice retina after implantation with titanium dioxide array nanowires modified with gold nanoparticles (a), blind mice without any implantation (b) and control (c) [67, 69, 82].*

prepare the appropriate prosthesis due to discerption of the retina as a layered structure with different electrical conductivity for each layer which the inner layers have higher resistivity in comparison to outer layers such as retinal epithelial pigment and membrane [83].

However, among the different research, simulation of photovoltaic materials, as well as silicon and titanium nanowires functionalized by gold nanoparticles that have the ability to receive the light signals and change the light signals to the electrical signals, are attracting the interests [68, 84]. Also, photovoltaic nanowires started the new generation of materials with extracellular electrical simulation and conjunction with the cells that are remaining the main challenges as implants used for retinal regeneration (**Table 2**).

light signals to the electrical signals [41, 85]. **Figure 4** is showing the process of turning light signals to the electrical signals used for regeneration of retinal photoreceptor. Also, sensing the light and electron travels between the *n-type*, *p-type* silicon will cause to the preparation of local extracellular electrical simulation, and conjunction between nanowires and cells as explained earlier. However, the gold nanoparticles with one free electron in the outermost layer of orbital play a vital role in improving the sensitivity of light perception in composition whit coaxial silicon nanowires [86]. Therefore in most of the nanowires have been produced for the regeneration of retina, gold nanoparticles loaded on the surface of nanowires.

**Nanowire In vitro In vivo Cell responses Refs**

Retinal progenitor cells — Cells developed on the place that short

nanowires aggregated

electrospun nanofibers.

— — [59]

microarray.

formation.

blind mice.

transfer.

Silicon — — [62]

Dorsal root ganglion — Cells successfully surrounded the

*n-type* silicon Mice retinal cell — The nanowires showed good cell

mice

— Subretinal

— Glial cell did not overgrow the neurons

— Nanowires embedded with cells strongly

Short nanowires have done better interaction with cells in comparison to

may be due to topographical of nanowires.

and nanowires did not have a significant effect on the morphology and RNA

distributions even though the nanowires do not permit the neural network

Array nanowires could transfer the neural signals and partly recover the vision of

nanowires, and in vitro light senses showed the ability of produced nanowires for senses the light and neural signal

Implant connected to inner nuclear layer [66]

[53]

[55]

[56]

[57]

[60]

[67]

[69]

(rat)

(pigs)

Iridium wire — Subretinal

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

> Rod and cone photoreceptor, ganglion cells and bipolar cells

Cortical neural stem

cells

*The in vitro and in vivo responses of nanowires.*

— Subretinal

Poly (ecaprolactone)

Poly (ecaprolactone)

Gallium phosphide

Parylene/ silicon

Gallium phosphide

Titanium dioxide

*n-type*/*p-type* silicon

**Table 2.**

**127**

Another example of using the same construction introduced by Tang et al. [67] use titanium dioxide nanowire loaded by gold nanoparticles. Also, they show that titanium dioxide nanowire loaded by gold nanoparticles with size 10 nm have the ability to efficient electron injection into the nanowires and implant as photorecep-

In the past years, nanowires with various structures but the same proposition for the regeneration of retina, recovery of vision have been developed, and their performance has been investigated. The researchers found that nanowires loaded with gold nanoparticles, showed a robust potential compare with cheapest and devices

tor simulation in the rat retina success upon photo-illumination [67].

#### **4.3 Light sensation**

Nanowires have been explored extensively as a component of photovoltaic to improve the efficiency of sensing light for retinal applications. The use of single nanowire as photovoltaic nanostructures present the several crucial advantages, which may leverage to produce robust, high efficiency and compatibility with cells. The simple example of sensing light and converting the light signals to the electrical signals are solar cells made from *n-type* and *p-type* silicon. Briefly, the *p-type* silicon produced by materials that have one free place for accepting one extra electron on the outer layer of orbital despite the *n-type* silicone which produced by elements and has one extra electron in the outer layer of their orbital and electron is not involved in any bonding. However, light absorption by the *n-type* silicon layer will cause to the movement of an extra electron to the empty orbital of *p-type* silicon, and this electron movement between the *n-type* and *p-type* silicon layers lead to changing the


#### **Table 2.**

prepare the appropriate prosthesis due to discerption of the retina as a layered structure with different electrical conductivity for each layer which the inner layers have higher resistivity in comparison to outer layers such as retinal epithelial pig-

*blind mice without any implantation (b) and control (c) [67, 69, 82].*

*The immunohistochemical graph of glial cells from mouse have been cultured on gallium nanowires, the cells stained green by glial fibrillary acidic protein (GFAP) and cells nuclei stained blue by 4,6-diamidino-2 phenylindole (DAPI) (A), SEM image from rat dorsal root ganglion cell surrounded a single a coaxial* ntype*/*p-type *silicon nanowire (B), SEM image from interface between the mice retina (RPE) and titanium dioxide array nanowire modified by gold nanoparticles (C), and the response of UV-light-evoked in the blind mice retina after implantation with titanium dioxide array nanowires modified with gold nanoparticles (a),*

However, among the different research, simulation of photovoltaic materials, as well as silicon and titanium nanowires functionalized by gold nanoparticles that have the ability to receive the light signals and change the light signals to the electrical signals, are attracting the interests [68, 84]. Also, photovoltaic nanowires started the new generation of materials with extracellular electrical simulation and conjunction with the cells that are remaining the main challenges as implants used

Nanowires have been explored extensively as a component of photovoltaic to improve the efficiency of sensing light for retinal applications. The use of single nanowire as photovoltaic nanostructures present the several crucial advantages, which may leverage to produce robust, high efficiency and compatibility with cells. The simple example of sensing light and converting the light signals to the electrical signals are solar cells made from *n-type* and *p-type* silicon. Briefly, the *p-type* silicon produced by materials that have one free place for accepting one extra electron on the outer layer of orbital despite the *n-type* silicone which produced by elements and has one extra electron in the outer layer of their orbital and electron is not involved in any bonding. However, light absorption by the *n-type* silicon layer will cause to the movement of an extra electron to the empty orbital of *p-type* silicon, and this electron movement between the *n-type* and *p-type* silicon layers lead to changing the

ment and membrane [83].

**Figure 3.**

*Regenerative Medicine*

**4.3 Light sensation**

**126**

for retinal regeneration (**Table 2**).

*The in vitro and in vivo responses of nanowires.*

light signals to the electrical signals [41, 85]. **Figure 4** is showing the process of turning light signals to the electrical signals used for regeneration of retinal photoreceptor. Also, sensing the light and electron travels between the *n-type*, *p-type* silicon will cause to the preparation of local extracellular electrical simulation, and conjunction between nanowires and cells as explained earlier. However, the gold nanoparticles with one free electron in the outermost layer of orbital play a vital role in improving the sensitivity of light perception in composition whit coaxial silicon nanowires [86]. Therefore in most of the nanowires have been produced for the regeneration of retina, gold nanoparticles loaded on the surface of nanowires.

Another example of using the same construction introduced by Tang et al. [67] use titanium dioxide nanowire loaded by gold nanoparticles. Also, they show that titanium dioxide nanowire loaded by gold nanoparticles with size 10 nm have the ability to efficient electron injection into the nanowires and implant as photoreceptor simulation in the rat retina success upon photo-illumination [67].

In the past years, nanowires with various structures but the same proposition for the regeneration of retina, recovery of vision have been developed, and their performance has been investigated. The researchers found that nanowires loaded with gold nanoparticles, showed a robust potential compare with cheapest and devices

supplied into the aligned nanofiber [26] and how nanofibers can simulate the extracellular matrixwith loading the gold nanoparticles into the nanofibers which

Nanowires have had a substantial impact on retinal applications and still, have great potential to advance therapeutic implants for retinal regeneration. The development of new structures, and their incorporation into the simulation of the extracellular matrix, extracellular electric and light senses may lead to improvement of advanced structure for developing artificial retina. However, challenges still need to be addressed in controlling the local charges and light sensation improvement. It is believed that engineered nanowires with high efficiency will be increasingly used in retinal implantations. In recent years, several in vitro and in vivo reports have indicated the possibility of a significant effect of nanowires on the recovery of vision that lost due to retinal degeneration. Another challenge that must be

addressed is the extracellular matrix to create a 3D scaffold, where it did not discuss in reports that have been done for nanowires usage in vision recovery, due to a limitation in synthesizing of nanowires. Also, it is crucial to discover the key factor promoting the assemblies of different layers of the retina and create specific scaffolds for polarization and construction of cells for transferring the neural signals to the brain. Developing nanowires to control the neural signals and guide the cells for polarization will be useful for engineering complex architecture as

This research was supported by the Shinshu University, Nano Fusion Technology Research Group, Division of Frontier Fibers, Institute for Fiber Engineering

(IFES), Interdisciplinary Cluster for Cutting Edge Research.

The authors declare no competing interests.

Finally, we envisage the use of stem cells incorporation of smart nanostructures and instruct the formation and regeneration of retina. Smart nanostructures with the ability to control the neural signals and simulation of the extracellular matrix could potentially circulate inside the retina and repair by cell adhesion, and in conjunction with smart nanostructures followed by transferring the adjusted signals to the brain in order to form clear vision. Therefore, our team has suggested to use the carbon nanowires to prepare the appropriate scaffold that can support both extracellular matrix and extracellular electric for improving the cell adhesion and

done by our team [24].

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

light sensation.

**6. Conclusion**

well as the retina.

**Acknowledgements**

**Competing interests**

**129**

#### **Figure 4.**

*Schematic of electron movement and holes toward the n-type and p-type silicon at the neural cell membrane for simulating the light senses. Light with receive to the n-type silicon containing the positive ions causes to the movement of electrons to the p-type silicon layer containing negative ions cause to senses the light and transfer produced faradic current to the cells [69]. (Refer to ACS ChemMatters online archive 2013–2014).*

for vision recovery lost due to retinal degeneration. Such observation emphasizes that nanowires are starting point in the progress for regeneration and implantable artificial photoreceptors.
