Tiny plastic spheres, called nanospheres, could help take the sting out of chemotherapy by delivering anticancer drugs more effectively and safely, according to Australian researchers.

When anticancer drugs are injected into the blood, they are recognized as toxic foreign agents and are 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 entire body is affected.

"You poison your whole body with these things," said Dr. Martina Stenzel, a polymer scientist from the University of New South Wales, who will present her team's research on the subject at the Australasian Polymer Symposium in Hobart, Australia, this week.

"The cancer may be [destroyed], but the patient has to recover from the treatment," she added.

Stenzel said the holy grail of drug delivery is to find a way of getting a drug straight to the cells it is supposed to be treating, and ensuring it is released slowly at the right concentration.

Search and destroy mission

Stenzel and colleagues at the university'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 seek out cancer cells and slowly release the drug directly into them.

Stenzel and her team have been experimenting with about 50 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 recognize 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 said 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 said the ideal would be for biodegradable polymers to be used so the nanospheres do not build up in the body.  But the nanospheres cannot be too biodegradable or they will not survive the trip through the bloodstream to their target.

The research team recently received two Australian Research Council grants for the research and are talking to a commercial partner.