Pollution fighter turns clot buster

A material normally used to clean up car exhaust fumes could one day be used in dressings and surgical equipment to prevent severe skin infections and blood clots. It might even help combat infections by the MRSA superbug, a newly filed patent claims.

What these medical problems have in common is that they can be treated with nitric oxide (NO). This gas is able to regulate blood pressure, stop thrombosis – blood clotting in the vessels – and is a powerful antibacterial agent. However, applying NO to the right areas and at the right levels is a major challenge. “As nitric oxide is toxic in large quantities you have to be able to deliver the right amount to the right place,” says Russell Morris, a chemist at the University of St Andrews in the UK. And because the gas is very reactive and quickly breaks down in the body, it is hard to find a way to deliver it to a specific site. But Morris thinks it will be possible to release NO onto the skin at precisely controlled rates using the same technology that catalytic converters use to scrub the gas from car exhaust. Some converters do this by trapping NO in a compound called a zeolite, then breaking it down into harmless nitrogen and oxygen. Zeolites are aluminosilicate compounds with a porous honeycomb structure. Other molecules can easily become trapped in the spaces. By doping the material with positively charged ions, NO can be pulled into the zeolite’s pores, making the compound very effective at storing the gas. Honeycomb cavitiesNow Morris and his colleagues, along with cardiovascular researchers Ian Megson and Adriano Rossi at the University of Edinburgh, UK, have begun testing whether zeolites can be used medically to store NOand deliver the gas to where it is needed (patent application WO 2005/003032). They plan to exploit the fact that when a zeolite is dry, it absorbs NO into its honeycomb cavities, but when exposed to moisture at body temperature, it releases the gas. And because some ions bind the gas more than others, Morris says he hopes to find a way to precisely control the rate of release by choosing the right type of doping for the zeolite.In test-tube experiments, the team found that nitric oxide released from zeolites into human blood prevented platelet aggregation – the first stage of blood clotting. They have also begun testing zeolite-impregnated dressings on human skin. These could be particularly useful for older people as their wounds tend to heal more slowly and are more susceptible to infection. The dressings might even provide protection against infections such as the antibiotic-resistant bacterium MRSA, which is increasingly common in UK hospitals.Zeolites could also help in major operations or procedures where blood is diverted outside the body. “Whenever blood is in contact with a foreign material, it can induce inflammation and thrombosis,” says Megson. So a zeolite coating in the tubes used in bypass surgery or kidney dialysis could be a simple way to prevent these problems, he says. The canulas used for intravenous drips may also benefit from such coatings.The zeolites Morris and his colleagues are using release all their gas within a few hours. The next step is to develop ones that can keep releasing gas for longer, and at a greater variety of rates.(Source: New Scientist, February 2005)