The risk of infection from medical implants can be reduced if the implants are coated with an antibacterial polymer, claim chemists in the US. 

Over half the hospital acquired bacterial infections that arise in patients are caused by medical implants, such as catheters, prosthetics and sensors. In response to this, Mark Schoenfisch of the University of North Carolina and fellow researchers have developed polymer coatings that prevent bacteria sticking to implant surfaces.

Implant-derived infections are difficult to treat because the bacteria stick to the implant, creating a thin film or 'biofilm', explained Schoenfisch. Bacteria within biofilms are often resistant to conventional antibiotics. 'Unfortunately, the lack of a suitable treatment often leaves extraction of the contaminated device as the only viable option for eliminating the biofilm,' said Schoenfisch. 

Implants coated with antibacterial polymers can resist biofilm formation, enabling them to better integrate with the patient's tissue. The polymer coatings are loaded with antimicrobial drugs. In some cases the drugs are slowly released from the polymer matrix; in others, biodegradable polymers gradually break down and free the drugs. These approaches mean that high local concentrations of the drugs can be used without exceeding the overall toxicity level in the rest of the body. 

'With an aging population that is increasingly active, biomedical implant use will continue to rise,' said Schoenfisch. He suggests future research should be aimed at increasing the efficacy of the coatings by combining several of the antibacterial strategies. 

Michael J Spencelayh