biosensor
/ BY-oh-sen-ser /
Living things are superb at recognising specific molecules: an enzyme grips only its matching substrate, an antibody latches onto only its target the way a lock accepts one key. A biosensor borrows one of these biological recognisers and wires it to an electronic readout, so the body's own molecular matchmaking becomes a number on a screen.
Concretely, a biosensor is a chemical sensor whose recognition layer is a biological component — an enzyme, antibody, DNA strand, or even whole cells — fixed onto a transducer. When the target binds or reacts, the transducer turns the event into an electrical, optical, or other signal whose size reflects how much target is present.
Because biological recognisers are so selective, biosensors can pick a single substance out of a messy real-world sample like blood or food with little cleanup, which is why the home glucose meter became a worldwide success. Their weakness is fragility: the biological layer can denature with heat, drying, or time, so biosensors often have a limited shelf life and a narrower operating range than rugged purely chemical sensors.
A blood-glucose strip carries the enzyme glucose oxidase, which reacts with glucose and produces a tiny electric current; the meter reads the current and instantly displays the blood-sugar level — a biosensor in everyday use by millions.
A biological molecule does the recognising; electronics do the reporting.
Every biosensor is a chemical sensor, but not every chemical sensor is a biosensor — the defining feature is a biological recognition element.