“This is one of the first applications of nanotechnology to healthcare and offers a clinical technique that is significantly better than what exists today,” said Charles Lieber of Harvard University. “A nanowire array can test a mere pinprick of blood in just minutes, providing a nearly instantaneous scan for many different cancer markers. It’s a device that could open up substantial new possibilities in the diagnosis of cancer and other complex diseases.”

The devices contain silicon nanowire field-effect transistors, incorporating both p- and n-type nanowires. Attached to the nanowires are monoclonal antibodies that act as receptors for cancer marker proteins. When a marker protein attaches to an antibody it changes the conductance of the nanowire according to the protein’s surface charge and the doping of the wire.

For example, a protein with a negative surface charge will increase the conductance of a p-type silicon nanowire but reduce the conductance of an n-type wire. The presence of both p- and n-type wires helps to prevent false positive results.

The researchers made devices that were detected the protein markers prostate-specific antigen (PSA), PSA-α1-antichymotrypsin, carcinoembryonic antigen and mucin-1. Doctors generally look for the presence of PSA and PSA-α1-antichymotrypsin to diagnose prostate cancer. Each nanowire sensor chip contained about 200 individually addressable devices, as well as a microfluidic channel for introducing the sample.

“Our results show that these devices are able to distinguish between molecules with near-perfect selectivity,” said Lieber.

The devices detected concentrations of 0.9 pg/ml in undiluted serum samples. The researchers believe their technique has the advantages of high sensitivity, the ability to test for several different markers simultaneously, and the provision of real-time testing without the use of labelling.

Lieber and colleagues also customized their devices to detect telomerase, a ribonucleoprotein complex found to be active in at least 80% of all known human cancers. To do this, they functionalized silicon nanowires with oligonucleotide primers complementary to the telomerase binding site. Introducing a cell extract containing telomerase decreased the conductance of p-type nanowires as telomerase is positively charged. The scientists say they could measure telomerase binding and activity down to a ten-cell level without amplification.

The researchers reported their work in Nature Biotechnology.