WHAT IS A BIOSENSOR?
Biosensors, also known as biological sensors, are instruments that, through physicochemical processes, allow us to monitor specific biological variables. Although not always the case, they usually combine biological and physical-chemical elements.
Biosensors, which are small analytical devices, emerged in the 1960s when Clark and Lyons proposed the immobilization of an enzymatic layer on electrical detectors, thus creating the first "enzymatic electrode".
These biosensors are increasingly becoming substitutes for a wide range of analytical techniques because they allow rapid, direct and reliable analysis. In addition, they are being increasingly used in medicine, the environment and industry in general.
WHY ARE THEY SO IMPORTANT TO THE FUTURE OF MEDICINE?
The use of tools that allow a physician to make a diagnosis is crucial in medical practice. One or more laboratory studies must be performed to investigate each pathology. These studies provide valuable information that, on many occasions, help diagnose, determine treatment and/or determine the patient's prognosis. The healthcare system has needed to develop new technologies that are cheaper and faster to use due to the high cost of equipment, the need for qualified personnel to perform and interpret studies, and the time often required to perform them.
This can be clearly seen in biosensors, which are devices that use particular biological reactions mediated by enzymes, immunosystems, tissues, organelles or cells to identify chemical compounds by thermal or optical electrical signals. Biosensors measure directly and continuously, are inexpensive, allow quantitative detection of very low concentrations, and can be integrated into a control system.
SOME EXAMPLES OF BIOSENSORS IN COMMON MEDICAL USE:
The mercury thermometer and other modern thermometers.
Home pregnancy tests.
Rapid test for streptococcus, infections such as influenza, HIV, or human immunodeficiency virus and hepatitis C.
Blood oxygen monitors.
Glycemia monitors.
Heart rate monitors.
Blood pressure monitors.
HOW ARE THESE BIOSENSORS MADE?
A sensor may be considered ideal for a variety of reasons, although each use may require specific characteristics. Biosensors must be small, inexpensive, easy to transport, capable of being used and interpreted by inexperienced people, have high sensitivity and specificity, be accurate and maintain their characteristics after multiple uses, have adequate resolution and adequate response speed.
Each biosensor is composed of at least three parts:
1. Biological sensor: first, there must be a biological component capable of selectively recognizing the desired analyte. This biological element must remain immobilized, be specific for the analyte and remain stable under the conditions of use and storage. We refer to any type of living substance that has the ability to respond to a specific target. Therefore, the same biological sensor is not valid for any type of biological sensor, since its use depends on the threat it is intended to combat. A culture of microorganisms or a group of enzymes can serve as biological sensors.
2. Transducer: Secondly, a physical-chemical transducer is required that can convert the physical-chemical change into a measurable signal. It takes the data from the biological sensor and enables the detector to produce accurate results.
3. Detector: and finally, the result of the analysis performed by the device is communicated through the detector of a biosensor. This must have a processor that can amplify and process the recorded signal so that it can be used as useful information. It can be thermal, visual or other, but the important thing is that it tells us exactly what we want to know.
WHAT TYPES OF BIOSENSORS ARE THERE, AND IS THERE A CLASSIFICATION?
Indeed, there are many types of biosensors, and three different classifications: according to the type of biosensor, according to the type of transducer and according to the use.
According to the type of biosensor: three main categories can be distinguished according to the basis of the biomaterial that will be used to identify the analyte under study.
1. Enzymatic biosensors: an enzymatic biocatalyst is used that transforms the analytes into quantifiable products.
2. Affinity biosensors: these can detect oligonucleotides or antibodies. Both are fully compatible with the analyte, either by means of a DNA probe or by the presence of an antigen-antibody reaction.
3. Cell-based biosensors: which use cells or microorganisms to detect their analytes.
According to the type of transducer: they are classified into five categories:
1. Electrochemical transducers: which convert the analyte-biological interaction into an electrical signal.
2. Potentiometric transducers: these measure voltage level, amperometric transducers measure current intensity, impedometric transducers measure impedance and conductimetric transducers measure conductivity.
3. Optical transducers: which have a common function: to measure variations in the properties of light.
4. Piezoelectric transducers: are measured by direct changes in mass caused by the formation of the antigen-antibody complex.
5. Thermometric transducers: last but not least, thermometric transducers can detect heat produced by exothermic enzymatic reactions.
According to their use: in medical practice there are many types, but among the most important we find four categories:
1. The "wearables", i.e., those that patients wear constantly. Some can even be placed under the skin. These biosensors can remain under the skin for months or years. They can change chemically to monitor various bodily functions. An app on the phone can collect all this information and share it with the doctor, caregiver or anyone else you want.
2. Second, those used for screening or rapid detection of common diseases, such as disposable HIV or Covid tests.
3. Thirdly, those that seek self-monitoring of different variables that allow patients to empower themselves and improve their daily parameter controls, such as glycemia in diabetic patients.
4.Finally, those that seek to carry out medical inspections, such as those related to food.
A GLIMPSE INTO THE FUTURE
Biosensors are a remarkable scientific innovation that has changed the way infectious agents are detected and certain essential parameters are monitored in medicine. There has been a shift from conducting microbiological investigations that required time, trained personnel and expensive machinery to employing innovative devices that are more sensitive, faster and cheaper. Biosensors that are fully reversible and regenerable and that can function in situ on complex samples and are biocompatible for in vivo operation will be the focus of future study.
The emergence of new technologies such as nanosensors and wearables indicates that advances in this field of science will continue to occur in the coming years, meaning that early diagnosis and patient monitoring will become increasingly easy, convenient, reliable and cost-effective. Advances in other fields, such as molecular biology, information technologies, biomaterials, microelectronics and biotechnology, also contributed to advances in biosensor research.
Biosensors are rapidly being incorporated into our daily health routines. New sensor technologies improve health. Future biosensors are the focus of researchers. These biosensors have the potential to improve health in ways we cannot yet conceive.
About the author:
Verónica Lovera Rojas graduated as a medical doctor in 2022 with concentration in the areas of surgery and gynecology. She has spent the past 8 years working as a medical writer and researcher, writing technical articles on a wide variety of topics in the medical field. She is currently practicing at a hospital and working as a professional medical writer.
About the translator / editor:
Brian Hoy has over 20 years of experience in the medical device industry and business formation, supporting the full lifecycle with global scope. Brian consults for industry and provides general advisory and off-hours support.
SOURCES
Lechuga, L. M., & De Lorenzo, V. The use of biosensors in medicine and environment. Csic.es.
https://digital.csic.es/bitstream/10261/43117/1/Publicaciones%20%20no%20%2014%20%20El%20uso%20de%20biosensores.pdf
Hernán, C. R., & Lorena, B. D. Use of biosensors in medical practice. Edu.uy.
http://www.nib.fmed.edu.uy/seminario_ib/2019/Uso%20de%20biosensores%20en%20la%20pr%C3%A1ctica%20m%C3%A9dica%20(2019)%20Monograf%C3%ADa%20Hern%C3%A1n%20Castillo.pdf
Biosensors and your health. The National Institutes of Health.
https://salud.nih.gov/recursos-de-salud/nih-noticias-de-salud/biosensores-y-su-salud
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