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Sadaqat M H. Types of biosensors and their application in the detection of microorganisms. KJMS 2025; 9 (18) :32-44
URL: http://kjms.knu.edu.af/article-1-61-en.html

Biosensors are devices for measuring the amount of analyte and chemical and biological reactions, which consist of a biological receptor, a transducer, an electronic part, and a display (depending on the type of biosensor). Various biosensors have been designed, the most important of which are optical biosensors, electrochemical and electronic biosensors, and mass-sensitive biosensors. Optical biosensors operate based on changes in the intensity, refraction, and reflection of light incident on a surface containing a bioreceptor and analyte (such as a microorganism), as seen in surface plasmon resonance and evanescent fiber-based biosensors. In fiber-optic biosensors, due to the large size of bacteria, the evanescent wave does not have significant penetration ability, which is increased by designing the optical fiber in a curved and U-shaped shape. In electrochemical and electronic biosensors, an electrode is used that converts the reaction into an electric current when the microorganism is attached to the bioreceptor, and in some cases, it also provides the ability to transmit information wirelessly. Mass-sensitive biosensors depend on the activity of piezoelectric materials, of which quartz is the most important material. Without a target virus or bacteria, the piezoelectric material has a certain oscillation frequency, which changes after the microorganism is attached and its value is measured. Today's standard methods such as culture, ELISA, PCR, and RT-PCR have good sensitivity and specificity but are time-consuming and expensive. In contrast, a biosensor is economically viable, easier to use, and provides instant test results.