16 August 2005: Nitric oxide to guard medical implants
Katharine Sanderson/Beijing, China
Medical implants for measuring glucose levels will only work effectively if they release nitric oxide (NO) at the same time, claim US researchers.
Blood glucose monitoring is vital for diabetes management, but this can mean routine blood sampling by pricking patients' fingers. Medical implants offer a promising alternative, but are not living up to that promise. Now Mark Schoenfisch, associate professor of chemistry at the University of North Carolina, Chapel Hill, could have the answer.
Cells stick to things, including implants, that don't belong in a cell's native environment. This leads to biofilm growth, which in turn leads to inflammation, scar-tissue growth, and ultimately infection. The process, called biofouling, prevents sensors from functioning. Biofilms create a barrier between the blood and the sensor, making detection difficult.
Schoenfisch has developed a system to prevent biofouling using NO-releasing sol-gels. The sol-gels are made from alkylsilane and aminosilane precursors, and can be made using mild reaction conditions.
They prevent biofouling by releasing NO, which the immune system uses to fight pathogens. 'We're trying to mimic how the body naturally deals with bacteria,' said Schoenfisch, who was speaking at the International Union of Pure and Applied Chemistry general assembly in Beijing.
The sensors can release NO for up to three weeks, and have been tested on rats with some success. 'There's a debate over whether you need NO release to be continuous or just over that initial acute phase - the first few days [after the implant is put in place],' Schoenfisch told Chemistry World. 'After NO release has stopped, cells will start to stick. In vitro studies show that once the NO release has gone it's no longer effective at reducing bacterial adhesion.'
Schoenfisch aims to combat this problem by making a sensor that will continuously release NO. 'I'm in the process of generating NO in bodies, biomimetically,' he said.