Nano-capsules For Drug Delivery

16 January 2005
Posted by Chris Smith.

Scientists in Australia have developed minute nanocapsules which can be used to target anti-cancer drugs to tumours, sparing other healthy tissue from side effects. The capsules, which measure about 1 micron across - or 1 thousandth of a millimetre - can be coated with an antibody which directs them from the bloodstream to a tumour. Once they are in the tumour, a quick blast with a harmless skin-penetrating laser producing near-infrared light causes the capsules to open up, discharging their contents. To make them, Frank Caruso and his team from the University of Melbourne, Australia, have engineered a polymer which they add to a suspension of drug particles so that the polymer forms a sphere enclosing the drug, several layers thick. They then add tiny gold particles 6 nanometres - that's 6 millionths of a millimetre across - which stick onto the surface of the polymer, rather like the speckles on a bird's egg. It's these gold particles which are sensitive to the laser light and allow the capsules to deploy their drug cargo at the desired time. When near-infrared light hits the gold spots they instantaneously melt, rupturing the capsule, but without harming the contents. The outermost layer of the nanocapsules consists of a fatty (lipid) layer to which a variety of antibodies can be attached to help target the capsules to specific tumours. So far they have tested the technique using a simple enzyme, called lysozyme, without any loss of activity from the enzyme when it was released from the capsule. The next step for Caruso and his team is to shrink the nanocapsules even further, and then test whether they can safely be administered to a living creature.

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