Plastic nanospheres to hunt out cancer
Friday, 9 February 2007
Nanospheres could help take the sting out of chemotherapy by delivering anticancer drugs more effectively and safely, say Australian researchers.
When anticancer drugs are injected into the blood, they are recognised as toxic foreign agents and quickly disposed of.
This means people undergoing chemotherapy have to put up with numerous intravenous injections to keep the drugs at an effective concentration.
This method of delivering drugs also has nasty side-effects because the whole body is affected.
“You poison your whole body with these things,” says Stenzel.
“The cancer may be [destroyed] but the patient has to recover from the treatment itself.”
So Stenzel says the holy grail of drug delivery is to find a way of getting a drug straight to the cells it’s supposed to be treating, and ensuring it is released slowly over a period of time at the right concentration.
Search and destroy mission
Stenzel and colleagues at the UNSW’s Centre for Advanced Macromolecular Design are among the first to explore the delivery of drugs in nanospheres, tiny plastic spheres.
These would contain, say, a week’s worth of drug that, once injected into the bloodstream would quickly seek out cancer cells and slowly release the drug directly into them.
Stenzel and team have been experimenting with about 50 different nanospheres, between 10 and 100 nanometres in diameter.
Each sphere is made of specially designed polymers. There’s a hydrophilic (water loving) coating to help get them through the bloodstream and a hydrophobic (oil loving) interior that can soak up the drug.
On the outside they are coated with special molecules, called ligands, that recognise and latch onto particular types of cells.
While further research is required to find the best ligands to target cancer cells, over healthy cells, the researchers have so far had some interesting results.
While some nanospheres seem to be toxic to human cells and kill them before they get a chance to deliver the drug, others latch onto the cells, or are taken up by them.
Once attached or inside the cell, the nanospheres release the drug slowly as planned.
Releasing the drug
Stenzel says in some cases the drug can simply slowly diffuse out of the nanosphere, in other cases, they have shown the nanospheres can dissolve in response to heat or acidity.
Cancer cells are slightly warmer than healthy cells and more acidic.
Stenzel says the ideal would be for biodegradable polymers to be used so the nanospheres don’t build up in the body.
But the nanospheres can’t be too biodegradable or they won’t survive the trip through the bloodstream to their target.
Stenzel and team recently received two Australian Research Council Discovery Grants for the research and are talking to a commercial partner.