A peptide found in tumour cells can trigger the release of drugs from a novel nanocarrier, claim South Korean scientists. They say their drug delivery system could make anticancer drugs more effective and reduce their side effects.

The disulfide cross-links in the micelle membrane are broken by glutathione, releasing the contents

Drug delivery systems transport drugs to diseased cells then release them, increasing their therapeutic action and preventing them from damaging healthy cells. Polymer micelles have been investigated as delivery systems but they lack stability and often release drugs at unwanted sites. Cross-linking the micelles makes them more stable but breaking the cross-links to release the drugs is problematic.

Sang Cheon Lee, at the Korea Institute of Ceramic Engineering and Technology, Seoul, and colleagues made polymer micelles linked by disulfide bonds. They loaded the micelles with methotrexate, an anticancer drug, and tested the micelles' ability to deliver the drug in a cancer cell culture.

They found that the micelles were readily taken up by the cells and, once inside, a peptide called glutathione broke the disulfide bonds, releasing the drug. Since tumour cells often contain higher levels of glutathione than normal cells, Lee suggests that these micelles could be used to directly target tumour cells. He adds that the micelles would be broken down by the body into harmless products after drug delivery.

'Since the cleavable cross-links can be tailored for other cellular signals, this novel nanocarrier technology has the potential to treat many diseases,' says Lee. He adds that the team's next aim is to adapt the system for molecular imaging.

Harriet Brewerton

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