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BUBBLES are not just for blowing. They could help treat disease by transporting drugs that would ordinarily break down in the body.

Small interfering molecules of RNA (siRNA) may cure diseases such as cancer by blocking protein production. However, siRNA is destroyed by enzymes in our blood, so a system to safely deliver it to the target is needed.

Now Calando Pharmaceuticals in Pasadena, California, is carrying out human anti-cancer trials with a 70-nanometre polymer bubble that envelopes the siRNA. Once in the bloodstream, it transports the siRNA to tumour cells using transferrin molecules attached to its surface – cancer cells are abnormally rich in transferrin receptors. When in the cancer cell, a change in pH causes the bubble to degrade, releasing the siRNA to interfere with DNA replication and slow the tumour’s growth.