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Textiles have been used in a broad range of medical applications and environments such as bandages and dressings, surgical gowns, bedding and hygienic items (Bartels, 2011). There has also been a significant increase in the use of specialised textile devices that help directly with patient care. Examples of this are highly technical medical products such as knitted stents for arteries and airways and braided materials for replacing tendons and ligaments. Nanofibres are seen to have great potential as a biomaterial which can

interact with living biological systems, such as human tissue. Tissue regeneration and engineering has become a complementary method to tissue or organ repair or replacement.

Various authors have postulated on using nanofibres as scaffolds to repair skin burns, muscle tissue and organ repair (Laine, 2013; Ma et al., 2005). One of the key factors in using fibrous tissue scaffolds is the degree of inflammatory response (Nguyen et al., 2012). Increasing the rate of cell growth can speed recovery and reduce scarring in burn injuries. This is done by providing an artificial framework along which cells can propagate. Natural connective tissues produced by the body have diameters from tens to hundreds of nanometres (Ma et al., 2005). Nanofibres are suited for mimicking this extra cellular matrix as the dimensions are similar. This similarity between electrospun fibres and the extracellular matrix allows rapid cell growth along the fibres which increases the rate of healing. When employing nanofibres the cells have directional support and can grow along the fibre length as shown in Figure 1.3. Nanofibrous webs have a high porosity and a very high surface area, this enables a high degree of surface functionality to be imparted if desired. The flexibility in processing means that different fibre morphologies and membrane densities can be produced, tailor made to the specific tissue environment (Burger et al., 2006). Using nanofibres as a scaffold in tissue engineering constructs will reduce this inflammatory response and also increase cellular attachment and proliferation compared to more traditional scaffolds (Smith et al., 2008).

Figure 1.3: Confocal microscope image of cardiac muscles extending along poly(lactic acid) (PLA) fibres produced by centrifugal spinning (Badrossamay et al., 2010).

Nanofibres are also applied in the area of drug and chemical delivery (Prausnitz and Langer, 2008). Drugs are typically administered intravenously, topically or through the gastrointestinal system. These techniques have disadvantages in that the drug may need to be delivered in a high dose at intervals throughout the day. This high dose of certain drugs can be toxic and it is known that with oral delivery there is an initial rapid release of drugs in to the bloodstream (Zeng et al., 2003b). For some drugs it is more suitable to have a lower but more consistent dosing profile than observed with oral delivery. The concept behind nanofibres drug delivery is to provide a high level of control over the release rate of a drug over a prolonged period of time. The high surface area and biodegradability of certain nanofibres has opened up avenues of research in this area. Two distinct approaches have been reported in the literature, for example, Chew et al. (2005) encapsulated a protein within the amorphous regions of a fibre and were able to control the release of a β-nerve growth factor by electrospinning in a biodegradable polycaprolactone scaffold. Alternatively membrane release method has been reported where the fibres act as a barrier between the skin and a concentrated gel (Bartels, 2011).

In this method the rate of drug delivery is controlled by the pore size and diffusion characteristics of a nanofibrous membrane.

In the drug encapsulation system Zong and co-workers (2002) found that the drug Mefoxin was completely released from sub-micron PLA fibres after 48 hours which led them to conclude that the drug was agglomerating at the fibre surface, increasing the rate of release. Katti et al. (2004) also found that Cefazolin, an antibiotic, could be loaded into poly (lactide-co-glycolide) fibres at a 30 % concentration without significantly changing the fibre diameter. Drugs incorporated into fibres can desorb from the fibre at a controlled rate allowing for the creation of drug delivery membranes. Figure 1.4 shows how the release profile differs between oral deliver and transdermal membranes. The combination of high doping capability and controllable release rates means that drug doped nanofibres are potentially useful for transdermal drug delivery.

Figure 1.4: Release rates of the drug, Rivastigmine, over time when taken a) orally every 12 hours and b) as a transdermal membrane (Smith and Uhl, 2009).

There is also the potential for applying nanofibres directly to a conventional medical textile materials in order to impart additional functional capability. This is typified

through a recent patent filed by Daniels et al. (2012) where conventional filaments are covered with a nanofibre sheath, Figure 1.5. The purpose of this enhancement is to induce coagulation, reduce blood loss and increasing the effectiveness of the wound dressing.

Figure 1.5: Nanostructure enhancement of conventional materials to aid haemostatic wound dressing (Daniels et al., 2012).

The research into using nanofibres in medical applications is intensive but is primarily focused on electrospun filaments. In comparison there is a paucity of research using centrifugal spun fibres in medical applications and it is proposed that centrifugal spinning could broaden the range of polymer feedstock that could be converted into ultrafine fibres for use in healthcare and therapeutics (Badrossamay et al., 2014).