Electro spun Nano fibrous Scaffold using Hybrid Polymer for Skin Tissue Regeneration

Introduction

Nanofibre (NF) is defined “as a slender, elongated thread-like object or structure on the nanoscale, from several hundred to several thousand nanometres”. The use of NF is seen to be an emerging, interdisciplinary area of research, which has several commercial applications that is set to dominate the field of tissue engineering along with having an economic impact globally. NF materials exhibit a high specific surface area that can accommodate on its surface a high proportion of atoms, which results in quantum efficiency, nanoscale effect of high surface energy, surface reactivity high strength etc. this makes NF useful in various aspects such as wound dressings, fuel cells, conduction polymers, tissue engineering to name just a few (He et al., 2008).

Electro spinning is the process of applying an electric force that results in fibre production. The main feature of electrospinning is that it can produce fibres with diameters with a measure in nanometers, which makes these fibres of a large surface area per unit mass. Thus, electro spinning has evolved to become a powerful tool especially for application in the field of tissue engineering and can be used to control NF into scaffolds. NFs that are generated by electro spinning improve cellular interactions. Therefore electrospun nano scaled fibrous scaffolds serve as tool for studying aspects of cellular interactions that eventually can lead to improved tissue formation, it is, moreover, a cost-effective technique that does not require sophisticated equipment and which can be used with an impressive variety of compounds (Sachot et al., 2014). Furthermore, the electro spun scaffolds can be functionalized by adding biochemical and mechanical cues to enhance cellular interactions for tissue engineering applications. But, the literature on specific cell interaction with these scaffolds is limited. In addition to this, significant challenges are faced in increasing the scaffolding thickness and pore size. If these challenges can be overcome then the use of electro spun NF may increase exponentially especially for tissue regeneration (Ladd et al., 2011).

Literature review

A wound is defined as damage or disruption to the normal anatomical structure and function. Wounds can arise from pathological processes that begin externally or internally within the involved organ. They can have an accidental or intentional aetiology or they can be the result of a disease process. A physiological response to the noxious factor results in bleeding, vessel contraction with coagulation, activation of complement and an inflammatory response.

Wound healing begins at the moment of injury and involves both resident and migratory cell populations, extracellular matrix and the action of soluble mediators. The mechanisms underlying the processes described above involve the following stages coagulation and haemostasis phase Immediately after injury (to prevent exsanguination and provide a matrix for invading cells that are needed in the later phases of healing) inflammatory phase divided into early and late, early inflammatory phase starts during the late phase of coagulation and activates the complement cascade and initiates molecular events, leading to infiltration of the wound site by neutrophils. The late inflammatory phase macrophages appear in the wound and continue the process of phagocytosis. Proliferative phase that starts on the third day after wounding and lasts for about 2 weeks is characterized by fibroblast migration, collagen synthesis, angiogenesis and granulation tissue formation, protrusion, adhesion and traction. Remodelling phase is the final phase and is responsible for the development of new epithelium and final scar tissue formation. This phase may last up to 1 or 2 years, or sometimes for an even more prolonged period of time (Velnar et al., 2009).

Adhesion, proliferation and differentiation of cells cultured on a scaffold constitute the basis of tissue engineering approaches. It is well known that cell-cell interactions direct cellular activity towards these behaviours and contribute to determining the fate of uncommitted stem cells The key design factors in developing a biomaterial aimed at triggering specific cellular responses are its chemical and mechanical surface properties and its architecture In today’s biomaterials for tissue regeneration, the trend is to be able to mimic the natural extracellular matrix (ECM) with its corresponding features, functions and hierarchical organization (Sachot et al., 2014).

The introduction of hybrid materials in regenerative medicine has solved some problems related to the mechanical and bioactive properties of biomaterials. When mixed with biodegradable polymers, the result is a synergic association that mimics the composition of many tissues of the human body and, additionally, exhibits suitable mechanical properties. Together with the development of nanotechnology and new synthesis methods, hybrids offer a promising option for the development of a third or fourth generation of smart biomaterials and scaffolds to guide the regeneration of natural tissues, with an optimum efficiency/cost ratio. Their potential bioactivity, as well as other valuable features of hybrids, open promising new pathways for their use in bone regeneration and other tissue repair therapies (Sachot et al., 2014).

Among the various fabrication methods available to produce 3D scaffolds, electro spinning is one of the most used techniques nowadays (Sachot et al., 2014). This technique is applicable to virtually every soluble or fusible polymer and is capable of spinning fibres in a variety of shapes and sizes with a wide range of properties to be used in a broad range of biomedical and industrial applications. The three stages of the electro spinning process is jet initiation (when the droplet is introduced formation of Taylor’s cone is seen at an angle of 49.3), elongation, and solidification (The solidification of the jet results in the deposition of a dry nano fibre on the collector) (Garg & Bowlin, 2011).

With increasing understanding of the intricate interactions between cells and their microenvironment in tissues, more attention is now focused on the preparation of scaffolds that can imitate the componential and structural aspects of extracellular matrix (ECM) to facilitate cell recruiting/seeding, adhesion, proliferation, differentiation, and neo tissue genesis; known as biomimetics (Wang et al., 2013).

Wang et al. (2013) enunciated the benefits of electro spinning nano fibres to mimic the ECM for potential use in scaffolding for tissue regeneration. Further to this, a study by Suganya et al. (2014), explored the use of Aloe Vera and silk fibroin which showed that the same would be most useful as tissue engineering scaffolds that can be implanted in the body to support a fast wound healing process with little scarring. Veleirinho et al. (2012) through in vitro and in vivo test revealed that hybrid poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/chitosan nano fibrous mats as scaffolds is feasible for use in skin engineering and also showed and improved healing process in rats. Another study by the same author Veleirinho et al. (2011) on a comparison between two biocompatible and biodegradable polymers (poly (3- hydroxybutyrate-co-hydroxyvalerate) [PHBV] and chitosan) revealed that hybrid fibers are better for use in tissue regeneration. On the same note Sankar proved that PHBV is effective for use as a scaffold in tissue regeneration. Ravichandran et al. (2012) displayed that of PLLA/PAA/Col I&II Inanofibrous (all in combination) scaffold with stem cell therapy would favour faster regeneration of the damaged skin tissues. Ma et al. (2014) specifically explored that the sandwich type of scaffold can be used for wound healing in extensive wounds.

Therefore, the above indicates that while many approaches exist for eventual use of electro spun nano fibers for skin regeneration, further review of the literature may shed light upon the main uses, techniques, drawbacks with recommendations for possible future works.

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Reference

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