الفهرس 
GENERAL INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Vesicular drug delivery systems such as liposomes; biocompatible phospholipid bilayer vesicles and niosomes; bilayer hydrated vesicles of non-ionic surfactants and cholesterol, offer distinct advantages over conventional and some novel drug carriers; these vesicles can act as drug reservoirs providing controlled and localized drug delivery. Modification of vesicle composition or surface characteristics can adjust the affinity for target sites and/or drug release rates. Biomedical devices such as intravascular catheters, prosthetic heart valves and orthopedic implants are increasingly used in clinical practice to improve survival rates and the quality of life of millions of patients. Unfortunately, despite advances in surgical techniques and prophylactic systemic antibiotics, these abiotic surfaces are prone to bacterial infections mostly caused by Staphylococcus aureus and Staphylococcus epidermidis. Early bacterial colonization of the medical device surface may take place in the first
5-hour post-operative period with adherence of biofilm matrix. This impedes device integration into the surrounding tissue and protects bacteria from the host immune system and the action of systemic antibiotics leading to the development of potentially life-threatening systemic infections and device malfunction. In this context, newer antimicrobial strategies were developed for combating device-related infections. These are essentially based on a passive approach, active approach or a combination thereof. Drug delivery and nanotechnology strategies involving functionalization of biomaterials by surface coating, impregnation or embedding have emerged as an effective approach for localized sustained antimicrobial control of medical biofilms. Lipid- and polymer-based drug carriers are the most exploited delivery systems in this respect.
Liposomes confer antiadhesive properties to abiotic surfaces and concentrate the antimicrobial pay load at the device surface and biofilm interfaces. In addition, liposomes can be designed to fuse with microbial cell membrane, enhancing the activity of antimicrobial agents and to bind with the device-related infection site. In contrast to liposomes, niosomes are more physicochemically stable, easily handled and less expensive, niosomes overcome the main limitations of liposomes. Niosomes are recognized to control the release and enhance the activity of antimicrobial agents including antibiotics and to interact with phospholipid membranes. The use of hydrophilic polyethoxylated surfactants such as Tweens and Brijs either alone or in combination with lipophilic surfactants (co-surfactant niosomes) confers bilayer hydrophilicity which enhances entrapment of water soluble drugs and may prevent bacterial adhesion at niosome treated surfaces. Accordingly, it could be hypothesized that co-surfactant antimicrobial-eluting niosomes may provide an alternative multifunctional approach to the control of bacterial biofilms at abiotic surfaces, a niosome application not explored to date.