Portable biosensors that use electric fields to detect molecular targets could pave the way to handheld diagnostic devices.
Researchers have used the device to detect thyroid-stimulating hormone (TSH) at the picomolar level — the first time anyone has used a field-effect transistor device to successfully detect a biological target in real blood serum without complicated molecular labeling or washing steps.
Field-effect transistors (FETs) detect changes in an electric field when a charged molecule binds to them. It’s a simple and elegant design with a lot of promise for developing on-the-spot biosensors, according to Alexey Tarasov, a research group leader at BioMed X Innovation Center in Heidelberg, Germany. But FETs do not work well in highly ionic solutions like blood or serum, which is the liquid portion of blood excluding the clotting proteins.
In those solutions, FETs run into a problem called Debye screening, whereby the surrounding ions mask the charges of the target molecule. The Debye screening length refers to the distance a molecule must be from the device to be detected. For most applications in...
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