The future of biolectronics - being able to diagnose diseases, detect poisons and monitor health instantly - may still seem far away, but it may be closer than you think.
Researchers understand what biochemical reactors they need to monitor and they know which microelectronics they would need to use. They have just been unable to combine them because measuring the ions in receptors within cell membranes destroyed the cells being measured.
A team at the Max Planck Institute say they have solved the problem and describe the coupling of a receptor to a silicon chip by means of a cell–transistor interface. True bioelectronics at its most basic level.
Many receptors are coupled to ion channels within cell membranes. When the corresponding ligand binds to its receptor, the channel is opened, allowing ions to stream into the cell. A team headed by Peter Fromherz writes of a novel, noninvasive sensor that involves coupling of the ion stream directly to a microelectronic device by means of a direct cell–chip contact.
Their test subject was the serotonin receptor, a protein that resides in the membrane and plays an important role in the nervous system. Blockers specific to this receptor are used clinically to reduce the nausea that results from chemotherapy and for the treatment of irritable bowl syndrome. The scientists allowed cells with many serotonin receptors in their membranes to grow onto a silicon chip with a linear arrangement of many transistor switches. For measurement, a cell that covers the tiny gap (gate) of one of the transistors must be selected. The voltage in this cell is controlled with a special electrode. If serotonin is then applied, the ion channels open; a stream of ions flows along a narrow gap between the cell and the chip into the cell. The resulting signal in the transistor voltage is proportional to the current across the membrane.
By using a variety of serotonin concentrations, a dosage–effect relationship can be determined. The application of new potential receptor blockers allows their effectiveness to be quickly and easily evaluated by means of their effect on the transistor signal. “With this coupling of a ligand-steered ion channel to a transistor at the level of an individual cell,” Fromherz says, “we have laid the foundation for receptor-cell–transistor biosensor technology.”
Source: Peter Fromherz, Max Planck Institute for Biochemistry, Martinsried, Germany.