Wanted: Super Sensitivity

Cells contain thousands of different proteins. Each protein has a different function. Ion channels are proteins whose main job is to move charged molecules across the cell membrane. And yet, scientists at ASU have decided to use ion channels in sensors designed to identify deadly biological agents that could be used in warfare.

Although these particular proteins aren’t generally used for sensing in the cell, they offer many advantages when used in sensor technology.

Other sensors generally rely on binding the biological agent itself to the sensor. But a molecule that is very similar to the bioagent may be able to bind to the sensor and give the same output. This causes many of the false positive signals in other sensors.

Detecting a bioagent that isn’t there might not be quite as bad as NOT detecting a bioagent that is present. But false positives can result in headaches for many. They can cause buildings to be evacuated, vital services to be shut down, and result in other disruptions that can be very costly. The ion channel is unique among sensor technologies because no actual binding of molecules takes place. The channel reacts to molecules in its environment; they don’t even have to touch.

In addition, the ion channel does not simply turn off or on when the bioagent is present. Current always flows through the ion channels. This current changes over time but in a way that can be described by statistics. Two very similar molecules will cause different changes in the current, allowing the sensor to distinguish between them.

Tracking changes in the current rather than a binding event makes the ion channel sensor super sensitive. The false positive rate is also very low. As such, the sensor could eventually be used in critical areas where it is essential that the sensor always be correct.—Linley Erin Hall