What Is a Biosensor?—A Terminological Guide From Biomolecular Recognition to Bioindicators

Biosensors are an integral part of modern medicine, are used in basic research, and are increasingly used by consumers as point-of-care and wearable devices. Meanwhile, the underlying technological approaches are rapidly expanding, including spectroscopic sensing, artificial bioreceptors, synthetic biological approaches, whole-cell biosensors, and artificial intelligence. With these diversifications in applications as well as technology, the scope and meaning of the term biosensor is blurring. This paper attempts to give an overview of the sensing approaches, with their physical, chemical, biochemical, and biological principles, and an overview of the fields of application, including nonliving systems and living systems. This leads to a comprehensive overview and a reappreciation of the term biosensor, including not only devices with a molecular biorecognition element and physico-chemical readout but also the sensing of living biological systems using physical and chemical methods, and the use of living biological systems for sensing purposes.