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Cover Story

Antimicrobial Coatings

Advances in medical devices have greatly improved diagnostic and therapeutic practices in medical care. But numerous undesirable complications such as bacterial infections, thrombosis, host rejection and insertion effects result in patient and tissue trauma and ultimately result in longer recovery times and higher medical costs.

Advances in coating materials and application methods are improving device profiles in important areas such as biocompatibility and biostability, and lowering the incidence of thrombosis and infection, creating new opportunities for device developers and for materials and manufacturing service suppliers.

Antimicrobial coatings can significantly improve the performance and implementation of devices in clinical practice. Advances in coating materials and application technology are increasing the types of devices that can meet clinical targets. Growth in device implants will track shifting patient demographics, as the effects of aging fuel the need for implants and diagnostic procedures. Partnerships between device designers and coatings developers will be a key success factor for the medical coatings sector.

According to Frost & Sullivan, the ability of antimicrobial coatings to address this issue expects to offer good growth opportunities.

Recent analysis from Frost & Sullivan found that the U.S. antimicrobial coatings markets earned revenues of $175.4M in 2005 with estimates to reach $558.7M by 2012.

Antimicrobial urinary catheters can prevent bacteriuria in hospitalized patients during short-term catheterization, depending on antimicrobial coating and several other variables.

Indwelling urinary catheters, which are used in 15% to 25% of short-term care patients during their hospitalization, confer a predisposition to bacteriuria. Catheter-associated urinary tract infection (UTI) is the most common type of hospital-acquired infection, accounting for approximately 40% of such infections and for most of the 900 000 patients with nosocomial bacteriuria in U.S. hospitals each year. Adverse consequences include local and systemic morbidity, secondary bloodstream infection, death, a reservoir of drug-resistant microorganisms, and increased health care costs.

Antimicrobial Coatings On Catheters

Catheters used for insertion into canals, vessels, passageways, or body cavities, usually to permit injection or withdrawal of fluids or to keep a passage open , made of Latex, Silicone, PVC, or Teflon.

These catheters when inserted for long time ( viz. Central Venous Catheters ) lead to infections inside the body. Many approaches have been made to reduce the incidence of these infections. These can be broadly classified into either patient management or catheter development. The former include improvements in skin antisepsis, care on insertion, non-occlusive permeable dressings and the development of antiseptic cuffs. The polymers used to make catheters have also been improved by the development of pliable non-deforming polyurethanes with decreased plasticizer content, extrusion of polymers under high temperature control, resulting in ultra-smooth surfaces, and the use of hydrophilic coatings. All these modifications have reduced microbial colonization, a pre-requisite of infection.

Another, more recent, approach for the prevention of Catheters related sepsis is the use of antimicrobials which have either been incorporated into, or used to coat, catheter polymers. One of the earliest antimicrobials to be incorporated into a polymer for the prevention of infection was gentamicin, bound to polymethyl methacrylate. Gentamicin has also been incorporated into bone cement or formulated as beads for the prevention of infections of prostheses. Dacron grafts have also been loaded with various antibiotics, but these have not been widely adopted. More recently, intravascular catheters have been coated with antimicrobial drugs, including antibiotics, antiseptics and metallic ions. When the devices are immersed in fluids, the antimicrobial is released, usually resulting in a high concentration initially being attained near the surface of the device, exceeding the MIC and MBC for potential pathogens.

Medical Coatings

Medical coatings such as our Advanced Heparin Coating (biocompatible and tissue compatible), Surface Active Antimicrobial Coating and Highly Lubricious Coating have applications in perfusion, infusion, implantable products, sensors, and in-vitro diagnostics.

The application of advanced heparin coatings to medical devices is necessary because they greatly reduce the foreign material response, which occurs when the medical device encounters the patient's tissue. The aggressive nature of this response causes protein deposition and platelet activation, leading to thrombus (clot formation); other responses include inflammation and fibrosis, prompting induced regression at the tissue device interface. All of these responses result in device failure and patient discomfort, with the outcome impacting on the patient's well being.

This highly biocompatible coating is ideal for many devices, such as catheters, vascular grafts and heart valves.

All implantable devices suffer from the common problem of device related infections, which invariably lead to morbidity and in some instances, mortality. This severe problem has a devastating impact on the healthcare system. Device related infections can be combated by the application of their novel Surface Active Antimicrobial Coating.

The advancement of devices such as catheters and guidewires through the tortuous pathways of the body is restricted by frictional forces that act between the device surface and the surrounding tissue. Such restrictions can lead to patient discomfort, prolonged procedures and an increased risk of tissue damage. In addition, such devices can suffer from thrombosis (blood clots) owing to the poor haemocompatibility of the materials employed. Such problems can be reduced through application of Lubricious Coating.

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