A biosensor is a biological detection system consists of a biological component combined with a transducer to perform measurement of a biochemical quantity. The development of biosensors started with the invention of enzyme electrodes by Leland C. Clark in 1962.
A typical biosensor includes a bioelement such as an enzyme, antibody, or a cell receptor, and a sensing element or a transducer. These two elements are combined together through a number of methods such as covalent bonding, matrix entrapment, physical adsorption and membrane entrapment.
Working Principle of Biosensors
Biosensors are operated based on the principle of signal transduction. These components include a bio-recognition element, a biotransducer and an electronic system composed of a display, processor and amplifier.
The bio-recognition element, essentially a bioreceptor, is allowed to interact with a specific analyte. The transducer measures this interaction and outputs a signal. The intensity of the signal output is proportional to the concentration of the analyte. The signal is then amplified and processed by the electronic system.
Types of Biosensors
Depending on the mechanism of transduction, biosensors are classified as follows:
- Resonant Biosensors – These sensors employ an acoustic wave transducer combined with the bioreceptor. Interaction between the analyte and bioreceptor forces a change in the mass of the bioreceptor. As a result, the resonant frequency of the acoustic transducer also changes, which is then evaluated and this value can then be interpreted by the end-user.
- Optical Detection Biosensors – These type of sensors include a silicon wafer to which protein molecules are attached through covalent bonds. The wafer is subjected to UV light which makes the antibodies inactive. The wafer is then diced and placed in the analyte, which encourages formation of diffusion grating that generates a signal which can be measured and amplified.
- Thermal Detection Biosensors – In these sensors, the immobilized enzymes are coupled with temperature detectors. A heat reaction is initiated when the analyte is made to interact with the enzyme. The concentration of the analyte can thus be evaluated with respect to the measurement of a heat reaction.
- Ion Sensitive Biosensors – These sensors work on the principle that the interaction of ions with a semiconductor changes the electric potential of the semiconductor surface. The potential changes can then be measured to evaluate the desired parameter.
- Electrochemical Biosensors – The principle behind the operation of these sensors involves the generation of ions by various chemical events that change the electrical properties of the analyte solution. The concentration of the analyte is then measured with respect to this change.
Advantages of Biosensors
The key benefits of biosensors include the following:
- Rapid and continuous measurement
- High specificity
- Very less usage of reagents required for calibration
- Fast response time
- Ability to measure non-polar molecules that cannot be estimated by other conventional devices.
Applications of Biosensors
Some of the major applications of biosensors are listed below:
- Monitoring glucose level in diabetes patients
- Food analysis
- Environmental applications
- Protein engineering and drug discovery applications
- Wastewater treatment.
The trends in biosensor technology over the past 30 years have taken this equipment from simple and cheap components to the integration of several sensor systems into one unit including multiple analytes, making these systems smaller and tailored for mass production. The vision for the biosensor industry is to create microscale technology that will be suitable for performing sample preparation, analysis and diagnosis all with one chip.