**4.2 Wound dressing**

*Nanofibers - Synthesis, Properties and Applications*

reduction of *S. aureus* [28].

**4.1 Health applications**

deliver therapeutics and drugs [31].

Eu or Dy, were recommended [32].

*Natural biopolymer electrospun nanofibers [30].*

the composition of polymer and fibre morphology [26].

**4. Applications of electro spun nanofibers (ESNF)**

nanofibers or on their surfaces. The polymer degradation, release profile, and release pathway of antibacterial drugs from electro spun nanofibers has a linkage with the release mechanism of antibacterial drugs which may be regulated through

Antibacterial drugs encapsulated in electro spun nanofibers have been proved to sustain the antibacterial property over a longer time compared to the un-encapsulated form. A sodium alginate electro spun nanofibers loaded with ciprofloxacin was developed by a team and it was tested for its antimicrobial activity against *Staphylococcus aureus*. The minimum inhibitory concentration [MIC] of ciprofloxacin required is found to be 0.125 μg/mL through this study [27]. Similarly, another team worked on developing nisin nanofibers/cellulose acetate which resulted in approx. 99.9%

Electrospinning offers many advantages like control over morphology, porosity and composition using very simple equipment. Due to its different applications in various fields like filtration products, biomedical applications, and tissue engineering to produce artificial blood vessels, non-woven fabrics, fuel cells, fibre mats etc. [29]. Electrospinning technology has been used for the fabrication and assembly of nanofibers into membranes, which have extended the range of potential applications in the biomedical, environmental protection (**Table 1**), nano sensor,

electronic/optical, protective clothing fields and various other fields [30].

The ESNF have shown great capacity in the human healthcare applications, for tissue or organ repair and regeneration, as biocompatible and biodegradable medical implant devices, in medical diagnostics and instrumentation, as protective fabrics against environmental and infectious agents in hospitals and as vectors to

For drug delivery or bio separation, nanofibers with strong paramagnetic properties prepared by the coaxial technology, such as Gd2O2S, possibly doped with

**Materials Solvent system Materials Solvent system**

Wheat protein HFIP Whey protein Acidic aqueous solution

Cellulose acetate Acetone/DMAc Chitosan TFA Chitin HFIP/PBS Hyaluronic acid DMF/water

Silk fibroin Formic acid Fibrinogen — Gelatin TFE/HFIP Elastin Water Collagen HFIP Soy protein HFIP

For controlled delivery of drugs, molecular medicines, body-care supplements and therapeutics nanofibers are used as a promising tool by cosmetics and pharmaceutical industries. To give an example such as DNA which is attached covalently to a patterned array of carbon fibre and inserted into cells by centrifuging these cells onto the array will not affect cell's viability and the expression of genes encoded by

**86**

**Table 1.**

The naturally extracted bioactive agents using electrospinning technique have been majorly promoted for the development of advanced level of dressings which paves way for rapid and efficient wound repair. Electrospun scaffolds consists of several advantages over the traditional dressings for the treatment of chronic as well as acute wounds, high absorption of exudates from the site of wound, efficient exchange of gases and nutrients for cell's proliferation, protection of the injured tissue, and the possibility to release functional molecules [34].

The distinctive features of ESNF scaffolds such as their inter-fibre and intrafibre pores and high surface area stimulate the fibroblastic cells response by rapidly initiating cell signalling pathways. Additionally, electrospinning technique can be used because of its application in the fabrication of cosmetic masks which are used for skin cleansing and skin healing. The high surface area of an electrospun skin mask facilitates the flow of additives from and to the skin (**Figure 3**) [30].

Many crude extracts of plants have been successfully encapsulated into electrospun fibres, such as *Centella asiatica,* baicalein, green tea, *Garcinia mangostana*, *Tecomella undulata*, *Aloe vera*, *Grewia mollis*, chamomile, grape seed, *Calendula officinalis*, *Indigofera aspalathoides*, *Azadirachta indica*, *Memecylon edule* and *Myristica andamanica* which has been used for wound healing [34].

ESNF has been effectively explored as a wound healing dressing material. By developing nanofibers to provide topographical and biological cues, the migration

**Figure 3.**

*Various strategies used to prepare suitable wound dressing [31].*

and infiltration of repairable cells can be improved. Once the nanofiber-based scaffolds have been optimised accordingly in vitro for the promotion of cell migration and/or delivery of biomolecules they will be subjected for wound healing evaluation in vivo using a mouse, rat, or rabbit model [33].

#### **4.3 Tissue engineering**

In tissue regeneration, biocompatible and biodegradable fibrous scaffolds are usually preferred over traditional scaffolds because of their uniqueness and capacity to provide the target cells or tissues with a local environment by imitating the extracellular matrix. Hence, the use of ESNF in tissue engineering is increasing day by day [30].

Osteogenic properties in medicinal plants such as *Cissus quadrangularis (*CQ ) and Asian *Panax ginseng* root have been suggested for regeneration of bone. The combined effect of CQ and hydroxyapatite (HA) has been explored by producing PCL-CQ-HA electrospun scaffolds. Proliferation of human foetal osteoblasts (hFOBs) on the composite scaffolds and increased adhesion was observed. Furthermore, increased levels of mineralisation and osteocalcin expression were detected which are fundamental in bone formation [34].

Bio or natural polymers (hyaluronic acid, alginate, collagen, silk protein, fibrinogen, chitosan, starch, and poly (3-hydroxybutyrate-*co*-3-hydroxyvalerate (PHBV)) have been mainly focused by the researchers until recently for tissue engineering, because these polymers showed excellent biocompatibility and biodegradability. However, in recent years, attempts have been made to utilise a wide range of natural and synthetic polymers for the regeneration of new tissues, specifically cartilage tissue, dermal tissue, and bones.

A synthetic polymer poly (lactic acid-co-glycolic acid) (PLGA) is the ideal material for tissue regeneration because of its tuneable and biodegradable nature, easy spinnability, and the presence of multiple focal adhesion points [30].

#### **4.4 Food industry**

ESNF is used for the encapsulation of plant extracts with the aim of preserving the integrity and controlling the release of the active ingredients in food processing and packaging. Electrospinning majorly offers the advantage of being a costeffective manufacturing procedure that operates at room temperature and it is compatible with most edible polymers and materials approved for food contact in these sectors [34].

A hydrophobic prolamin, Zein which can be extracted from corn consists of marvellous film-forming properties with a high thermal resistance. Earlier, zein films were used as edible coatings on tomatoes to delay the colour changes, weight losses, and on nuts to delay rancidity during storage. However, the zein based electrospun mats may provide additional attributes for food packaging [35].

Functional molecules extracted from plants have been exploited for prolonging food shelf-life and avoiding bacteria colonisation in food packaging applications. In one of the modern studies, electrospun mats of β-cyclodextrin (PVA/CEO/β-CD) and PVA containing cinnamon essential oil (CEO) have been developed and tested against *S. aureus* and *E. coli*. The combination of CEO with β-CD enhanced the antibacterial action of this essential oil [34].

A cost competitive plant protein which is a soy protein is partially purified and concentrated from soybeans in various forms, such as soy protein concentrate, defatted soy flour, and soy protein isolate (SPI). Though there is a great amount of interest in developing soy protein as an electrospinning matrix, pure soy protein cannot be electrospunned easily.

**89**

**Table 2.**

519 ± 127 nm

450 ± 110 nm

*Electrospun Nanofibers: Characteristic Agents and Their Applications*

**5. When are electrospun nanofibers not a good option?**

infiltration (decrease due to smaller average pore size) [36].

Electrospinning is an impressive technique however, the size of the fibres being nano, is a disadvantage when it comes to control. The limited control of the pore size (Electrospun scaffold) is a diameter dependent which reflects on the cellular

Another reason being the degradation effect (introduced in the latter half of the introduction). The rapid degradation of nanofibrous constructs can adversely affect the ability of the scaffolds to support tissue growth. The structure of the nanofibers plays an important role, especially when it comes to nanoscale, the high surface area to volume ratio serves as the reason for its selection. However, in case of degradation effect, due to this property, the nanofibers are prone to hydrolytic degradation. Hence long-term processes should not employ such scaffolds as before the entire process (observation, selection or any other research studies) is completed, the culture will have no support to grow [36]. Crystallinity in polymers can treat this problem however the size of the fibres (diameter) are still a variable with a high probability of variation (purpose dependent and needs a lot of testing before it can be finally put into use). The poor infiltration of cells into scaffolds is still an issue to deal with, especially when we want to add various properties into nanofibers. As mentioned in the introduction, electrospinning is an easy to setup and scalable technique. The cost parameter is in our favour whereas the volume imposes some difficulties in terms of production. It is quite difficult to produce a large volume scaffold and if the critical factors do not meet the threshold level the final structure might not be at its best form. This will drastically affect the application part. This will also affect special properties like antimicrobial/inflammatory/oxi-

dant. The release of the drug will be questionable in such cases (**Table 2**).

required which introduces more complication [37].

438 ± 156 nm Electrospun, aligned, and randomly oriented PCL

430 ± 170 nm Electrospun, aligned, and randomly oriented PLLA

300–900 nm Electrospun PLGA nanofibers on top of microfibers

**Diameter Fibre composition Application**

*Variations in polymer nanofibers size in ligament and tendon tissue engineering [36].*

The drug loading process when it includes a high amount of drug can result in a burst. When we submerge the fibres in aqueous solution (prone to hydrolytic degradation), the antimicrobial properties (e.g., antibiotics) are released in a short duration (might not last till it's required). This issue can be solved by using different set-ups. We have learned that electrospinning technique is an easy to set-up one, here if we want to use such nanofibers for a longer duration, a different set-up is

When environmental factors are taken into consideration, most frequently relative humidity is studied. When this parameter is a settable, considering higher RH leads to thinner fibre diameter, an appropriate high RH level could be selected.

657 ± 183 nm Electrospun, aligned PU In vitro culture of human ligament

In vitro culture of meniscal fibrocartilage

In vitro culture of human tendon stem cells

In vitro culture of porcine MSCs

cells and human MSCs

fibroblasts

*DOI: http://dx.doi.org/10.5772/intechopen.97494*

*Nanofibers - Synthesis, Properties and Applications*

in vivo using a mouse, rat, or rabbit model [33].

detected which are fundamental in bone formation [34].

cartilage tissue, dermal tissue, and bones.

antibacterial action of this essential oil [34].

cannot be electrospunned easily.

**4.4 Food industry**

these sectors [34].

**4.3 Tissue engineering**

and infiltration of repairable cells can be improved. Once the nanofiber-based scaffolds have been optimised accordingly in vitro for the promotion of cell migration and/or delivery of biomolecules they will be subjected for wound healing evaluation

In tissue regeneration, biocompatible and biodegradable fibrous scaffolds are usually preferred over traditional scaffolds because of their uniqueness and capacity to provide the target cells or tissues with a local environment by imitating the extracellular matrix. Hence, the use of ESNF in tissue engineering is increasing day by day [30]. Osteogenic properties in medicinal plants such as *Cissus quadrangularis (*CQ ) and Asian *Panax ginseng* root have been suggested for regeneration of bone. The combined effect of CQ and hydroxyapatite (HA) has been explored by producing PCL-CQ-HA electrospun scaffolds. Proliferation of human foetal osteoblasts (hFOBs) on the composite scaffolds and increased adhesion was observed. Furthermore, increased levels of mineralisation and osteocalcin expression were

Bio or natural polymers (hyaluronic acid, alginate, collagen, silk protein, fibrinogen, chitosan, starch, and poly (3-hydroxybutyrate-*co*-3-hydroxyvalerate (PHBV)) have been mainly focused by the researchers until recently for tissue engineering, because these polymers showed excellent biocompatibility and biodegradability. However, in recent years, attempts have been made to utilise a wide range of natural and synthetic polymers for the regeneration of new tissues, specifically

A synthetic polymer poly (lactic acid-co-glycolic acid) (PLGA) is the ideal material for tissue regeneration because of its tuneable and biodegradable nature,

ESNF is used for the encapsulation of plant extracts with the aim of preserving the integrity and controlling the release of the active ingredients in food processing and packaging. Electrospinning majorly offers the advantage of being a costeffective manufacturing procedure that operates at room temperature and it is compatible with most edible polymers and materials approved for food contact in

A hydrophobic prolamin, Zein which can be extracted from corn consists of marvellous film-forming properties with a high thermal resistance. Earlier, zein films were used as edible coatings on tomatoes to delay the colour changes, weight losses, and on nuts to delay rancidity during storage. However, the zein based electrospun mats may provide additional attributes for food packaging [35].

Functional molecules extracted from plants have been exploited for prolonging food shelf-life and avoiding bacteria colonisation in food packaging applications. In one of the modern studies, electrospun mats of β-cyclodextrin (PVA/CEO/β-CD) and PVA containing cinnamon essential oil (CEO) have been developed and tested against *S. aureus* and *E. coli*. The combination of CEO with β-CD enhanced the

A cost competitive plant protein which is a soy protein is partially purified and concentrated from soybeans in various forms, such as soy protein concentrate, defatted soy flour, and soy protein isolate (SPI). Though there is a great amount of interest in developing soy protein as an electrospinning matrix, pure soy protein

easy spinnability, and the presence of multiple focal adhesion points [30].

**88**
