Biosensors

DEFINITION: Devices that use biological molecules or cells to detect and measure chemicals, biological agents, or physical conditions and then use nonbiological components to convert the data into signals or readouts.

SIGNIFICANCE: Biosensors have attracted significant attention for their potential in countering the use of chemical and biological weapons by terrorists and for their applications as on-site forensic analytical devices at crime scenes. Biosensors potentially offer sensitive and rapid detection of harmful organisms and substances in food and water supplies. Such instruments have demonstrated usefulness for measuring many substances that are of interest to forensic science, such as toxins, drugs of abuse, poisonous chemicals, and DNA.

Biosensor devices differ in the biological components they use for sensing chemicals. Examples are enzymes, antibodies, receptors, and whole cells. The most common biological components used in biosensors are enzymes and antibodies. Different types of biological components result in different types of signals that must be converted into readouts.

Biosensors can be classified according to the ways in which the detection is mediated by their biological components is converted into measurable signals. After the initial recognition of a chemical species by the biological component, a biosensor generates a readout signal in a process called transduction. At least five different kinds of transducers are used in biosensors: amperometric transducers involve the movement of electrons resulting from a bio recognition event among three electrodes; potentiometric transducers exploit biological sensor-induced changes in the movement of ions, which result in the generation of an electric potential; thermal transducers utilize heat from biorecognition events that may be exothermic or endothermic reactions; optical transducers make use of the production or absorption of light resulting from biological recognition of detected chemicals or biological molecules; and piezoelectric transducers react to changes in mass-produced by biological recognition of target chemicals or biological molecules.

The physical component of a biosensor’s transducer, which is in contact with the biological sensor, may comprise electrodes, semiconductors, and optical constructions such as optical fibers and nanoparticles. Most biosensors use electrochemical types of transduction, such as amperometric and potentiometric methods, and enzymatic, antibody, or DNA biological recognition components.

Working and Organization

A biosensor contains an external and an internal interface. In the first step, at the external interface of the device, the substance being measured (analyte) binds with the biological recognition component of the biosensor. In the second step, at the internal interface, the biological recognition system interacts with the transducer component, and this produces a physical or chemical response. This response may involve the production of hydrogen ions, other ions, or electrons for amperometric, potentiometric, and conductimetric biosensors. A second type of transducer response may involve the biologically coupled production or absorption of light (fluorescence, chemiluminescence, or visible light). A third type of transducer response is a change in mass at the transducer, such as occurs in piezoelectric (or microelectromechanical) systems. A fourth type of transducer response involves changes in temperature for thermal or calorimetric systems. The physical or chemical response produced by the transducer is processed and amplified to generate a readout signal that serves to indicate the presence and amount of a substance of interest.

Applications

Nanotechnology—that is, the application and study of the structuring and behavior of materials at the nanometer scale—has also been used in making biosensors. Gold, cadmium selenide, and zinc selenide nanoparticles and single-walled carbon nanotubes are among the nanoscale substances that are used to make biosensors to detect metal ions, biological molecules, and even viruses such as those responsible for strains of influenza (such as influenza A and the avian influenza virus H5N1).

Challenges in the use of biosensors arise from the need for small, portable devices, the inherent instability of most biological molecules and cells, and the need for highly sensitive devices that can measure a wide range of substances simultaneously. Biosensors used at crime scenes by forensic investigators and in national defense applications must perform reliably and produce quick results under field conditions. In the United States, in addition to their uses by law-enforcement personnel and by national security agencies for the detection and prevention of bioterrorist attacks, biosensors are used for many applications, including environmental monitoring, quality control during food processing and the processing of pharmaceuticals, and monitoring of agriculture. A common type of nanobiosensor is used by people with diabetes to monitor blood glucose levels. Such devices are typically worn on the upper arm or abdomen, depending on the model.

Bibliography

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Cooper, Jon, and Tony Cass, editors. Biosensors: A Practical Approach. 2nd ed., Oxford UP, 2004.

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Ganechary, Pavan Kumar, et al. “Development of Nanomaterial Based Biosensors for Forensic Applications.” Materials Today: Proceedings, vol. 95, 2023, pp. 88–100. ScienceDirect, doi:10.1016/j.matpr.2023.10.124. Accessed 13 Feb. 2026.

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Karunakaran, Chandran, et al. Biosensors and Bioelectronics. Elsevier, 2015.

Kress-Rogers, Erika, editor. Handbook of Biosensors and Electronic Noses: Medicine, Food, and the Environment. CRC Press, 1997.

Vigneshvar, Senthilkumaran, et al. “Recent Advances in Biosensor Technology for Potential Applications—An Overview.” Frontiers in Bioengineering and Biotechnology, vol. 4, 16 Feb. 2016. Frontiers Media, doi:10.3389/fbioe.2016.00011. Accessed 13 Feb. 2026.