Scientists have built a tiny biological computer made of DNA that might be capable of medical diagnosis and treatment.

The biocomputer senses abnormal messenger RNAs produced by genes involved in certain types of lung and prostate cancer (as a proof of principle) and releases an anticancer drug, also made of DNA, which damps expression of the tumor-related gene. Billions of the computers could easily fit inside a human cell.

Researchers hope it will be the precursor of future “smart drugs” that roam the body, fixing disease on the spot.

Benenson, Y., Gil, B., Ben-Dor, U., Adar, R. & Shapiro, E. Nature, published online, doi:10.1038/nature02551 (2004).