Novel infection-resistant surface coatings: A bioengineering approach
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Implant-associated infections Implant-associated infections are a significant healthcare problem and a major cause of post-surgical morbidity and mortality in patients. Over half of the two million cases of nosocomial infections that occur in the United States annually are associated with indwelling devices.1,2 Catheters alone account for hundreds of thousands of infections each year resulting in a significant cost and burden to the healthcare system.3 Although less common than catheter-based bloodstream infection, infections established on surgical implants and devices are considerably harder to treat because they require longer antibiotic regiments and repeated surgical procedures.4 In the case of orthopedic trauma surgeries, up to 10% of fracture fixators and 85% of external fixators typically become infected and have to be managed with several weeks of systemic antibiotic therapy.5–7 Surgical treatments usually involve the removal of the infected nail or pin followed by insertion of a replacement. Infection of implanted devices with particularly virulent multiresistant strains, such as methicillin-resistant Staphylococcus aureus (MRSA), may necessitate multiple, and often traumatic, surgical procedures that can be psychologically devastating in older patients, with
additional risk and cost. Furthermore, infections are likely to play a larger role than is currently appreciated because lowlevel infections are difficult to detect radiographically and because biofilm bacteria resist culture, hindering traditional detection methods.8,146 The treatment of device-associated infections is far more complex than the simple administration of antibiotics. When an implant is inserted into the host tissue, small biomolecules, including extracellular matrix (ECM) proteins (e.g., fibronectin, fibrinogen, and collagen), adsorb onto the material surface to form a conditioned protein layer conducive to the adherence of free-floating planktonic bacteria. The adhered bacteria then rapidly proliferate, recruit other cells, and produce sticky secretions to form dense three-dimensional communities of attached (sessile) cells called biofilms1,9 (Figure 1). Antibiotics and other antimicrobial compounds show greatly reduced antimicrobial activity against organisms living within biofilm communities. Consequently, bacterial biofilms are notoriously difficult to eradicate. Despite decades of prophylactic antibiotic use, high infection rates continue, particularly with the emergence of lethal multi-drug-resistant strains. This is due, in part, to the
Xiaojuan Khoo, Boston University, MA 02215, USA; [email protected] Mark W. Grinstaff, Boston University, MA 02215, USA; [email protected] DOI: 10.1557/mrs.2011.66
© 2011 Materials Research Society
MRS BULLETIN • VOLUME 36 • MAY 2011 • www.mrs.org/bulletin
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NOVEL INFECTION-RESISTANT SURFACE COATINGS: A BIOENGINEERING APPROACH
surface properties. The principal function of these adhesion-resistant coatings is to keep bacteria numbers sufficiently low to impede the development of a biofilm so that the host defensi
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