NANOFIBERS AND PHARMACEUTICAL APPLICATIONS
- Electrospinning and Nanofibers
Electrospinning is a simple and versatile technique that utilizes electrostatic forces to produce very fine fibers of polymer ranging from submicron to nanometer sizes. The technique can be applied to generate fibers of a wide array of polymer types—synthetic, natural, biodegradable, non-degradable, or their blends. Although there are other conventional techniques for polymeric fiber fabrication such as phase separation, self-assembly, template synthesis, and mechanical drawing, electrospinning has gained much importance and is the preferred technique since it is relatively ease, cost effective, requires simple tooling, and is applicable for producing ultrafine fibers with simple step-up production that is not easily achievable with other conventional fiber-forming techniques. During electrospinning, a high voltage electric field, is applied to the polymer liquid (a solution or melt) resulting in ejection of a continuous jet strand from the eluting nozzle that accelerates toward the oppositely charged grounded collector. In the absence of any electric field the polymer droplet is held at the capillary tip by surface tension of the liquid 
Fig. Scheme of electrospinning process (www.inovenso.com) 
Nanofibers is a nano-object with the size of 1 billionth of a meter. The fibers are made through electrospinning, which is the most common and commercially used way of manufacturing nanofibers. Through this process, an electrified polymer solution is moved in a high voltage electric field to give elongated nanofibers. Many nanofibers are laid over one another to form a nano mat. A nano mat is a breathable fabric, but it is so small in size that it does not allow even the entry of bacteria. Based on these properties, nanofibers find huge applications in various field applications like filtration, catalysts, semiconductors, optical waveguides, fuel cells, composites, tissue repair, sensors, and scanning probe microscopy in industries such as mechanical, chemical, electronics, energy, automotive, aerospace, sensors, and instrumentation .
Fig. Commercial application areas of nanofibers
Electrospun nanofiber matrices show morphological similarities to the natural ECM, characterized by ultra fine continuous fibers, high surface-to-volume ratio, high porosity and variable pore-size distribution similar to the dimensions of basement membranes. Therefore, there has been tremendous effort to develop new applications based on materials produced by electrostatic processes in the biomedical and pharmaceutical field ranging from tissue engineering, grafts (blood vessel, tendon, nerve and mussel), anti-adhesion barrier membranes to scaffolds for the delivery of bioactive agents and drugs.
- Wound Healing and Wound Dressing
An interesting application of electrospun nanofibers is the treatment of large wounds such as burns and abrasions. It is found that these types of wounds heal particularly rapidly and without complications if they are covered by a thin web of nanofibers, in particular, of biodegradable polymers. Such nanowebs have suitable pore size to assure the exchange of liquids and gases with the environment, but have dimensions that prevent bacteria from entering. Mats of electro spun nanofibers generally show very good adhesion to moist wounds. Furthermore, the large specific surface area of up to 100 m2g-1 is very favorable for the adsorption of liquids and the local release of drugs on the skin, making these materials suitable for application in hemostatic wound closure. Further, multifunctional bioactive nanofibrous wound – healing dressings can be made available easily simply by blending with bioactive therapeutic agents (like antiseptics, antifungal, vasodilators, growth factors, etc.) or by coaxial electrospinning. Compared to conventional wound treatment, the advantage is also that scarring is prevented by the use of nanofibers .
Figure. Schematic showing a) the principal biomolecules present in the wound bed and involved in the healing process; b) the fabrication of nanofibrous meshes by electrospinning process; and c) the main approaches to provide electrospun fibers for the necessary properties for wound healing applications .
Fig. Wound healing application 
- Drug delivery and pharmaceutical composition
Nanofiber systems for the release of drugs or other functional compounds are generally not only of interest for wound healing or tissue engineering. Nanostructured systems for tumor therapy, but also for other types of therapies like inhalation therapy or pain therapy, are currently being investigated worldwide.
In an ideal case they have to fulfill versatile jobs in this function. The nano-objects are supposed to protect the drugs in the case of systemic application from decomposition, for example, in the blood circuit. Furthermore, they should allow controlled release of the drug at a release rate as constant as possible over a longer period of time, adjusted to the field of application. They have to be able to permeate certain membranes or barriers, respectively, for example, the blood/brain barrier and they are supposed to concentrate the drug release only on the targeted body area. Electrospun nanofibers may serve in this context as carriers for drugs and as controlled release agents. The domain of nanofibers loaded with drugs will most likely be of little importance for systemic therapy but of great importance for locoregional therapy that is, the fibers are localized at the exact part of the body that is supposed to be treated with the carried drug. A currently developing field of application is inhalation therapy based on nanorods. The reason is that the aerodynamic radius of such rods can be adjusted via the dimension of the rods in such a way that the drug carriers can be deposited at specific positions in the lung. This knowledge can be used to place rod – shaped drug carriers at specific positions in the lung for locoregional release. An advantage of rod-like in contrast to spherical drug carriers, furthermore, appears to be that the percentage of rods that remains in the lung after inhalation, and not exhaled, is significantly higher than in the case of spherical particles. The treatment of tumors, metastases, pulmonary hypertension and asthma are goals, but also the administration of insulin or other drugs via the lung. To be able to selectively adjust the aerodynamic diameters, the nanofibers fabricated by electrospinning have to be shortened to a defined axis ratio. This task can be achieved, for example, by laser or mechanical cutting. To control the aerodynamic radius via the density, highly porous fibers may be used. Inhalation therapy will have to be based on polymers that are biocompatible with particular emphasis on the specific reactions within the lung .
Fig. Schematic illustration for the nanofiber-based treatment of basal cell carcinoma (Biodegradable Nanofiber for Delivery of Immunomodulating Agent in the Treatment of Basal Cell Carcinoma)
- Cosmetic Applications
Nanofibers take the advantage of their unique properties and have extensive usage in cosmetics, tissue engineering, biomedical, filtering, composites, protective clothing, electrical and optical applications, sensors, and agriculture. Since nanotechnology allows production of value-added products, cosmetics produced by nanotechnological methods have attracted attention from every area. With the aid of nanofiber production methods, especially by electrospinning, mats with controllable pore sizes and fiber diameters can be obtained. Also, the novel approaches that have been shown to cosmetics led to consumption of more conscious cosmetic products including therapeutic products and products for skin health and renewal (such as facial masks for skin cleansing, skin healing, and skin therapy). All of the products mentioned above can be produced by using nanofibers .
 Viness Pillay et al., “Review of the Effect of Processing Variables on the Fabrication of Electrospun Nanofibers for Drug Delivery Applications”, Journal of Nanomaterials, Vol 2013, 2012
 Global Nanofiber Market 2016-2020., http://www.technavio.com/report/global-embedded-systems-nanofiber-market
 Electrospinning: Materials, Processing, and Applications, First Edition. Joachim H. Wendorff, Seema Agarwal, Andreas Greiner. (2012) Wiley-VCH Verlag GmbH & Co. KGaA.; Chp 9- Medicinal Applications for Electrospun Nanofibers.
 Review of the Effect of Processing Variables on the Fabrication of Electrospun Nanofibers for Drug Delivery Applications”, Journal of Nanomaterials, Vol 2013, 2012).
 Martina Abrigo, Sally L. McArthur, Peter Kingshott; Electrospun Nanofibers as Dressings for Chronic Wound Care: Advances, Challenges, and Future Prospects, Macromol. Biosci. 2014, 14, 772–792
 Garrett, Richard, et al. “Biodegradable nanofiber for delivery of immunomodulating agent in the treatment of basal cell carcinoma.” Fibers 3.4 (2015): 478-490.