Gold nanoparticles that mimic ‘good cholesterol’ could be used to treat people with high levels of cholesterol.
American researchers made synthetic high density lipoprotein (HDL), often called ‘good’ cholesterol, by covering gold nanoparticles with lipid molecules, and showed that it binds irreversibly to cholesterol (JACS 2009, 10.1021/ja808856z). They hope that it could one day be used to top up low levels of HDL found in the blood of patients with high cholesterol levels.
Cholesterol is made in the liver from fatty food. It is essential for normal functioning in the body, but high levels can cause problems, including narrowing of the arteries, heart attacks, strokes and increased risk of coronary heart disease. HDL binds to cholesterol and carries it back to the liver where it is broken down or removed as waste.
‘What we’ve done in the test tube is show that synthetic HDL not only looks like HDL but also functions like HDL,’ said Shad Thaxton, author and professor of medicine at Northwestern University, IL, US. Testing synthetic HDL in cell cultures will be the next big step, he says.
Gold is an ideal foundation for the nanoparticles, explains author Chad Mirkin, also at Northwestern. It is highly coloured, which allows researchers to track its activity using spectroscopy, and is also easy to make in a range of sizes and shapes. Mirkin adds that gold is generally considered safe for use in the body, and that gold nanoparticles are already used for diagnostic applications.
‘If you’ve got a raised cholesterol level you can lower your cholesterol by about 50% with a statin,’ says Bruce Griffin, a lipid and lipoprotein researcher at the University of Surrey, UK. But other problems, such as obesity, diabetes and high blood fat levels, are also associated with low levels of HDL. ‘One of the big pharmacological challenges has been to come up with a drug that increases HDL... there’s a long way to go, but you’ve got to start somewhere and I find this quite exciting.’
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