**1. Introduction**

324 Biomedical Science, Engineering and Technology

O'Connell, B.M. & Walsh, M.T. (2010).Demonstrating the Influence of Compression on

Parry, T.J., Brosius, R., Thyagarajan, R., Carter, D., Argentieri, D., Falotico, R. &Siekierka, J.

Rajamohan, D., Banerjee, R.K., Back, L.H., Ibrahim, A.A., Jog, M.A. (2006). Developing

Schwartz, R.S., Chronos, N.A. & Vivmani, R. (2004).Preclinical Restenosis Models and Drug-

Stone, G.W., Midei, M., Newman, W. et al. (2008).Comparison of an Everolimus-Eluting

Sun, N., Wood, N.B., Hughes. A.D., Thom, S. A. M. & Xu, X.Y. (2006). Fluid-Wall Modelling

Van der Hoeven, B.L., Pires, N.M.M., Warda, H.M., Oemrawsingh, P.V., Van Vlijmen,

Venkatraman, S. &Boey, F. (2007).Release Profiles in Drug-Eluting Stents: Issues and

Waksman, R. (2002). Drug-Eluting Stents: From Bench to Bed. *Cardiovascular Radiation* 

Walsh, M.T., Kavanagh, E.G., O'Brien, T., Grace, P.A. & McGloughlin, T.(2003). On the

Uncertainties. *Journal of Controlled Release*, Vol. 120, pp. 149-160.

Management. *American Journal of Medicine*, Vol. 115, pp. 547-533.

Vol. 128, pp. 347-359.

1903-1913.

Vol. 99, pp. 9-17.

*Medicine*, Vol. 3, pp. 226– 241.

*Endovascular Surgery*, Vol. 26, pp. 649-656.

*Cardiology*. Vol. 44, pp. 1373-1385.

*Current Pharmaceutical Design*, Vol. 10, pp. 357-368.

Artery Wall Mass Transport. *Annals of biomedical Engineering*, Vol. 38, pp. 1354-136.

(2005). Drug–Eluting Stents: Sirolimus and Paclitaxel Differently Affect Cultured Cells and Injured Arteries. *European Journal of Pharmacology*, Vol. 524, pp. 19-29. Rajagopal, V. &Rockson, S.G. (2003).Coronary Restenosis: A Review of Mechanisms and

Pulsatile Flow in a Deployed Coronary Stent. *Journal of Biomechanical Engineering*,

Eluting Stents: Still Important, Still Much to Learn*. Journal of the American College of* 

Stent and a Paclitaxel-Eluting Stent in Patients with Coronary Artery Disease: A Randomized Trial. *The Journal of The American Medicine Association*, Vol. 299, pp.

of Mass Transfer in an Axisymmetric Stenosis: Effects of Shear-Dependent Transport Properties. *Annals of Biomedical Engineering*, Vol. 34, pp. 1119-1128. Tanabe, K., Regar, E., Lee, C.H., Hoye, A., Van der Giessen, W.J.&Serruys, P.W. (2004). Local

Drug Delivery Using Coated Stents: New Developments and Future Perspectives.

B.J.M., Quax, P.H.A., Schalij, M.J., Van der Wall, E.E. & Jukema, J.W. (2004). Drug Eluting Stents: Results, Problems and Promises. *International Journal of Cardiology*,

Existence of an Optimum End-to-Side Junctional Geometry in Peripheral Bypass Surgery – A Computer Generated Study. *European Journal of Vascular and*  Many microorganisms are able to produce a wide range of amphipathic compounds, with both hydrophilic and hydrophobic moieties present within the same molecule which allow them to exhibit surface activities at interfaces and are generally called biosurfactants or bioemulsifiers. These surface-active compounds (SAC) are mainly classified according to their mode of action, molecular weight and general physico-chemical properties.

In literature, the terms 'biosurfactants' and 'bioemulsifiers' are often used interchangeably, however in general those that reduce surface and interfacial tension at gas-liquid-solid interfaces are called biosurfactants and those that mainly reduce the interfacial tension between immiscible liquids or at the solid-liquid interfaces leading to the formation of more stable emulsions are called bioemulsifiers or bioemulsans. The former group includes lowmolecular-weight compounds, such as lipopeptides, glycolipids, proteins, while the latter includes high-molecular-weight polymers of polysaccharides, lipopolysaccharides proteins or lipoproteins (Smyth et al., 2010a, 2010c).

In heterogeneous systems, biosurfactants tend to aggregate at the phase boundaries or interfaces. They form a molecular interfacial film that affects the properties (surface energy and wettability) of the original surface. This molecular layer, in addition to lowering the surface tension in liquids, also lowers the interfacial tension between different liquid phases on the interfacial boundary existing between immiscible phases and therefore can have an impact on the interfacial rheological behaviour and mass transfer.

When at interfaces (solid- liquid, liquid-liquid or vapour-liquid), the hydrophobic moiety of the surface active molecules aggregates at the surface facing the hydrophobic phase (usually the oil phase) while the hydrophilic moiety is oriented towards the solution or hydrophilic phase (mainly water). Their diverse functional properties namely, emulsification, wetting, foaming, cleansing, phase separation, surface activity and reduction in viscosity of heavy liquids such as crude oil, make them suitable for utilization for many industrial and domestic application purposes (Gautam & Tiagi, 2006; Franzetti et al., 2010a; Perfumo et al., 2010a; Satpute et al., 2010b).

During the past two decades biosurfactants have been under continuous investigation as a potential replacement for synthetic surfactants and are expected to have several industrial and environmental applications mainly related to detergency, emulsification, dispersion and solubilisation of hydrophobic compounds (Banat et al., 2000). In addition, biosurfactants present several advantages over surfactants of a chemical origin, particularly in relation to their biodegradability, environmental compatibility, low toxicity, high selectivity and specific activity at extreme temperatures, pH and salinity (Banat 1995a, 1995b). Due to all these properties, they have steadily gained increased significance in industrial and environmental applications such as bioremediation, soil washing, enhanced oil recovery and other general oil processing and related industries (Perfumo et al., 2010b). Furthermore, potential commercial applications in several other industries including paint, cosmetics, textile, detergent, agrochemical, food and pharmaceutical industries begin to emerge (Banat et al., 2000).

Numerous investigations in the field of biosurfactants/bioemulsifiers are leading to the discovery and description of many interesting chemical and biological properties and potential biomedical therapeutic and prophylactic applications. In this chapter we will focus on the most recent and appealing biomedical and therapeutic applications of biosurfactants and bioemulsifiers with special emphasis on the most recent results in the fields of biotechnology, nanotechnology and bioengineering.
