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Meet the cyborg cell. By attaching probes with nano-hairpin connectors to living cells, researchers have measured electrical currents from inside. They hope the probes will provide a useful way to monitor cells’ health.

A team at Harvard University conducted the study, which appears in Science. Though other probes can measure the currents in electrical impulse-producing cells–such as beating heart cells–none have given researchers the precision of measuring from inside. The probes designed in this study allowed researchers to successfully measure the electric pulses from cultured chicken heart cells’ beating.

One of the team’s challenges was getting the wires to kink into the hairpin shape–a difficult maneuver using traditional nanowire-making techniques. They noted if they stopped the wire as it formed, they could force it to bend.

The business end of the transistor sits on the pin’s bent tip and penetrates the cell. The two arms of the hairpin, which serve as electrical contacts, do not penetrate the cell deeply so minimise damage. In general, it is difficult to control the shape of nanowires, which are grown gradually on a substrate. But last year, [Charles M.] Lieber’s team reported that if you stop and restart this growth process, you can introduce a 120º kink. By kinking their wire twice in quick succession, the team created the sharp hairpin bend that they required. [Nature News]

The team also camouflaged the probe’s tip (which can be smaller than the diameter of a virus particle) with a lipid coating–fooling the cell into letting it inside.

The Harvard cell probes, described today in the journal Science, are three-dimensional, V-shaped silicon nanowires with transistors at their tips. They’re flexible and coated with two layers of lipid molecules, just as a cell is. When the transistor tip, which is about the size of a virus, encounters a cell, the cell pulls it inside. Lieber’s group found that the tips can also be removed gently, with no ill effects to the cell. They’ve used the transistor probes to take electrical measurements in single cells and are now using them to measure electrical activity in the groups of adjacent cells that form tissues. [Technology Review]

The team hopes that eventually such devices will prove useful in medical monitoring, and is planning tests to see if similar devices will work with neurons.

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Images: Science / AAAS