Transistor used for single molecule detection

An ultra-sensitive detector includes an antibody-coated ‘gate’ (brown rectangle, centre), which controls the current flowing through electrodes (gold lines). Credit: Eleonora Macchia

Technology

A sensor detects the light touch of a single molecule

Contact with just one antibody molecule regulates current flow through a transistor.

A millimetre-sized device that detects a single molecule demonstrates world-record sensitivity, according to the device’s creators.

Typical laboratory assays can sense a single molecule only if it has a label such as a fluorescent tag. To build a more flexible sensor, Luisa Torsi at the University of Bari Aldo Moro in Italy and her collaborators used a transistor as a base. In an ordinary transistor, the application of a voltage to a component called the gate can switch a current running between two electrodes ‘on’ or ‘off’. The researchers coated the top of a gate with antibodies that bind another antibody called human immunoglobulin-G (IgG). The binding of a single IgG molecule to the coating triggered the gate, controlling the flow of current through the transistor.

The team’s simulations suggested that in binding to an IgG molecule, a coating molecule changes shape. That causes neighbouring coating molecules to rearrange themselves, which affects the gate’s voltage. The authors say that the approach could be used to detect the protein byproducts of various diseases.