Nitric oxide-releasing membranes could coat the next generation of medical sensors, claim researchers in the US.

Mark Schoenfisch at the University of North Carolina and his peers have developed solidified gels (xerogels) and polymers that release nitric oxide (NO). These materials can be used to coat medical sensors, improving their performance and potentially minimising infection, said Schoenfisch.

Sensors provide a means of monitoring medically-relevant chemicals in the blood. However, the human immune system perceives these sensors as foreign bodies and launches an attack on them. As a result, biological material, including platelets and proteins, builds up on the sensor surfaces. This process, called biofouling, can lower sensor performance.

NO inhibits the immune response to foreign bodies and reduces platelet aggregation. Sensors coated in the NO-releasing materials have shown reduced levels of biofouling.

'Making chemical sensors work better in vivo is the holy grail in the chemical sensor field,' said Mark Meyerhoff, a bioanalytical chemist at the University of Michigan. 'Use of a naturally occurring small molecule such as NO, known to inhibit platelet function and reduce inflammatory response, represents an innovative strategy,' he said. 

The build up of bacteria on surfaces is another problem associated with sensors and medical implants. NO is also an antimicrobial agent; not only are the NO releasing membranes useful for making sensors more biocompatible but they could also reduce infections, said Schoenfisch. 

Schoenfisch suggests that future efforts should be made to increase the amount of NO that the polymers can generate. This has a finite limitation however and finding a way to mimic NO generation in the body is an 'attractive alternative,' he said.

Ian P Gray