Send Orders for Reprints to reprints@benthamscience.net Pharmaceutical Nanotechnology, 2014, 2, 23-34 23 The Multifaceted Potential of Electro-spinning in Regenerative Medicine Kieran Fuller, Abhay Pandit and Dimitrios I. Zeugolis * Network of Excellence for Functional Biomaterials (NFB), National University of Ireland Galway (NUI Galway), Galway, Ireland Abstract: The increased interest in nanotechnology has resulted in an intense investigation and development of nano- fabrication methods. Among the bottom-up approaches, electro-spinning has attracted great interest in recent years. The popularity of electro-spinning lays on the fact that it is a relatively simple and economic technique that enables production of large quantities of nano- to micro-meter range fibrous materials with various morphologies and architectural features. The versatility of electro-spinning is evidenced by the range of applications being utilised, including filtration, textiles, batteries, and tissue engineering and regenerative medicine. Specifically to biomedical applications, advancements in the electro-spinning setup have allowed the development of electro-spun mats that closely imitate native extracellular matrix assemblies and provide opportunities for localised and sustained delivery of therapeutics. Herein, we are discussing dif- ferent electro-spinning setups and their distinct benefits for regenerative medicine applications. Keywords: Architectural features, delivery of therapeutics/biologics, electro-spinning, nano- and micro-fibres, scaffold archi- tecture, tissue engineering. 1. INTRODUCTION The nanomaterial’s sector global market was worth $15.9 billion in 2012 and is expected to rise to $37.3 billion by 2017 with a compound annual growth rate of 19.1% [1]. Top-down nano-processes, such as lithography, deposition and etching, reduce large pieces of materials to nano-scale components. However, such technologies require large amounts of starting materials and are often associated with excessive waste generation. On the other hand, bottom-up nano-fabrication approaches, such as electro-spinning and self-assembly, are utilised to build three-dimensional hierar- chical constructs by putting together atomic and molecular components in a hierarchical fashion. Such technologies have minimal processing waste and are particularly favoured for biomedical applications. Among the various bottom-up processes, electro-spinning is favoured a means to fabricate sub-micron devices, largely attributed to its inherent versatil- ity and controllability [2, 3]. Indeed, to-date, numerous natu- ral and synthetic polymers [4, 5]; ceramics [6, 7]; and metal- lic materials [8, 9] have been electro-spun that have found applications in textile [10], filtration [11] and biomedicine [12] sector/industries. The rationale of using electro-spinning in biomedicine lays on the fact that this technology can create three dimen- sional fibrous scaffolds that closely imitate the nano- to mi- cro-scale intertwined fibrillar meshwork of the extracellular matrix [12-15]. The first paper using electro-spinning a means to develop an implantable device was published in 2002 [16]. Since then, a staggering number of peer-reviewed publications (12,087 papers; Source: Scopus; Term searched: electro-spinning); patents (75,300 patents; Source: Google *Address correspondence to this author at the Network of Excellence for Functional Biomaterials (NFB), National University of Ireland Galway (NUI Galway), Galway, Ireland; Tel: +353-(0)-9149-3166; Fax: +353-(0)- 9156-3991; E-mail: dimitrios.zeugolis@nuigalway.ie patents; Term searched: electro-spinning); clinical trials (2 trials; Source: ClinicalTRials.gov; Term searched: electro- spinning); and products (e.g. NovaMesh™, Nicast Ltd; HealSmart™, PolyRemedy ® Inc.; Bioweb™, Zeus ® Inc) have become available, clearly demonstrating the multifac- eted potential of this technology. In this review, we will dis- cuss how modifications in the electro-spinning setup allow (a) development of implantable devices with different archi- tectures for specific clinical targets (Fig. 1) and (b) function- alisation through the ability to deliver therapeutic molecules (Fig. 2). 2. ELECTRO-SPINNING SETUP AND PARAMETERS AFFECTING ELECTRO-SPINABILITY OF MATE- RIALS A typical electro-spinning setup is made up of a syringe containing the material to be extruded suspended in a highly volatile solvent; a syringe pump that controls the flow rate of the extrudate; a power supply that controls the voltage; a metallic spinneret; and a metallic collector. During extrusion, the electrostatic force, applied by the high voltage power supply, overcomes the surface tension and forms a Taylor cone. A jet ejection is formed at the tip of the metallic spin- neret and is subsequently attracted towards the grounded metallic collector. The initial ejection is in a uniaxial direc- tion, which subsequently develops into a conical envelope through electrostatic and fluid dynamic instabilities [17]. As the solvent evaporates, there is a significant reduction in the ejected material size, which results in fibre formation that is collected on the metallic collector. An alternative to the tra- ditional setups is needless electro-spinning. This is a tech- nique which is gaining increasing interest and there are vari- ous methods of electro-spinning without a needle such as bubble electro-spinning whereby a gas is passed through a solution and the bubbles disruption of the surface creates a Taylor’s cone [18], and another method uses a variety of 2211-7393/14 $58.00+.00 © 2014 Bentham Science Publishers