What is a Biosensor : Types & Its Applications

The first biosensor was invented in the year 1950 by American biochemist “L.L Clark”. This biosensor is used to gauge oxygen in the blood, and the electrode used in this sensor is named the Clark electrode or oxygen electrode. Afterward, a gel with glucose oxidize enzyme was layered on the oxygen-electrode to compute blood sugar. Correspondingly, enzyme urease was utilized with an electrode that was invented particularly for NH4++ions for calculating urea in fluids of the body such as urine and blood. There are three generations of biosensors available in the market. In the First type of biosensor, the reaction of the product disperses to the sensor and causes the electrical reaction. In the second type, the sensor involves in particular mediators between the sensor and the response in order to produce a better response. In the third type, the response itself causes the reaction and no mediator is straightly involved. This article gives an overview of a biosensor, the working of biosensors, different types, and its applications.


What is a Biosensor?

Biosensors can be defined as analytical devices which include a combination of biological detecting elements like a sensor system and a transducer. When we compare with any other presently existing diagnostic device, these sensors are advanced in the conditions of selectivity as well as sensitivity. The applications of these Biosensors mainly include checking ecological pollution control, in the agriculture field as well as food industries. The main features of biosensors are stability, cost, sensitivity, and reproducibility.

The short form of the biological sensor is known as a biosensor. In this sensor, a biological element is maybe an enzyme, a nucleic acid otherwise an antibody. The bio-element communicates through the analyte being checked & the biological reply can be changed into an electrical signal using the transducer. Based on the application, biosensors are classified into different types like resonant mirrors, immune, chemical canaries, optrodes, bio-computers, glucometers & biochips.

Main Components of a Biosensor

The block diagram of the biosensor includes three segments namely, sensor, transducer, and associated electrons. In the first segment, the sensor is a responsive biological part, the second segment is the detector part that changes the resulting signal from the contact of the analyte, and for the results, it displays in an accessible way. The final section comprises an amplifier which is known as a signal conditioning circuit, a display unit as well as the processor.

Main Components of a Biosensor
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Working Principle of Biosensor

Usually, a specific enzyme or preferred biological material is deactivated by some of the usual methods, and the deactivated biological material is in near contact with the transducer. The analyte connects to the biological object to shape a clear analyte which in turn gives the electronic reaction that can be calculated. In some examples, the analyte is changed to a device that may be connected to the discharge of gas, heat, electron ions, or hydrogen ions. In this, the transducer can alter the device linked convert it into electrical signals which can be changed and calculated.

Working of Biosensors 

The electrical signal of the transducer is frequently low and overlays upon a fairly high baseline. Generally, the signal processing includes deducting a position baseline signal, obtained from a related transducer without any biocatalyst covering.

The comparatively slow character of the biosensor reaction significantly eases the electrical noise filtration issue. In this stage, the direct output will be an analog signal however it is altered into digital form and accepted to a microprocessor phase where the information is progressed, influenced to preferred units, and o/p to a data store.

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Example

Before discussing the different types of biosensors and their uses, we have to discuss the simple example of this biosensor like Glucometer. This is most frequently used in different medical applications. We know that diabetes is one of the dangerous diseases that characterize the glucose levels within the blood of human bodies. So for diabetes patients, checking glucose levels within the blood is essential. For that, a glucometer is used as a biosensor to measure the glucose concentration within the human blood.
Generally, a glucometer includes a strip for testing.

This strip collects the blood sample and checks the glucose level within the blood. This strip includes a trigger as well as a reference-type electrode. Once a blood sample is poured on the strip, then a chemical reaction takes place to generate an electrical current that is directly proportional to the glucose concentration. The processor used in the glucometer is Cortex-M3 otherwise Cortex-M4 through the flow of current toward filter, amplifier, voltage converter, a display unit.


Evolution of Biosensor

The classification of Biosensors can be done into 3 generations based on the amount of incorporation of the separate component like the technique of connection of the bioreceptor molecule otherwise biorecognition toward the element of the base transducer.

In the 1st generation, the molecule of the bioreceptor is entrapped physically within the area of the base sensor after a discriminating membrane like a dialysis membrane. In the next generations, the achievement of immobilization can be done through covalent bonds on a properly customized transducer interface otherwise by inclusion into a polymer matrix on the surface of transduction.
In the 2nd generation, the individual components stay separate like control electronics, bio-molecule & electrode.

In the 3rd generation, the molecule-like bio-receptor turns into an essential element of the base sensing element whereas these definitions were possibly planned for enzyme electrode systems, related classifications are suitable to biosensors usually can be made. It is within the 2nd & 3rd generations of families that the main development attempt can currently be observed.

Features

A biosensor includes two main distinct components like Biological component such as cell, enzyme and a physical component like an amplifier and transducer.

The biological component identifies as well as communicates through the analyte for generating a signal that can be sensed through the transducer. The biological material is properly immobilized over the transducer & these can be frequently used numerous times for a long period.

Types of Biosensors

The different types of biosensors are classified based on the sensor device as well as the biological material that is discussed below.

Electrochemical Biosensor

Generally, the electrochemical biosensor is based on the reaction of enzymatic catalysis that consumes or generates electrons. Such types of enzymes are named Redox Enzymes. The substrate of this biosensor generally includes three electrodes such as a counter, reference, and working type.

Electrochemical Biosensor
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The object analyte is engaged in the response that happens on the surface of an active electrode, and this reaction may source also electron transfer across the dual-layer potential. The current can be calculated at a set potential.

Electrochemical biosensors are classified into four types

  • Amperometric Biosensors
  • Potentiometric Biosensors
  • Impedimetric Biosensors
  • Voltammetric Biosensors

Amperometric Biosensor

An amperometric biosensor is a self-contained incorporated device based on the amount of the current ensuing from the oxidation offering exact quantitative analytical information.

Generally, these Biosensors have reaction times, energetic ranges & sensitivities comparable to the Potentiometric-biosensors. The simple amperometric biosensor infrequent usage includes the “Clark oxygen” electrode.

Amperometric Biosensor
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The rule of this biosensor is based on the amount of the flow of current between the Counter Electrode and the working which is encouraged by a redox response at the operational electrode. Choosing analyte centers is essential for a wide selection of uses, comprising high-throughput medicine screening, quality control, problem finding and handling, and biological checking.

Potentiometric Biosensor

This type of biosensor provides a logarithmic reply by means of a high energetic range. These biosensors are frequently complete by monitor producing the electrode prototypes lying on a synthetic substrate, covered by a performing polymer with some enzyme is connected.

Potentiometric Biosensors
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They comprise two electrodes that are enormously responsive and strong. They allow the recognition of analytes on stages before only attainable by HPLC, LC/MS & without exact model preparation.

All types of biosensors generally occupy the least sample preparation because the biological detecting component is extremely choosy used for the analyte troubled. By the changes of physical and electrochemical the signal will be generated by in the layer of conducting polymer due to modifying happening at the outside of the biosensor.

These changes might be credited to ionic force, hydration, pH, and redox responses, the latter as the label of enzyme rotating above a substrate. In FETs, the gate terminal has been changed with an antibody or enzyme, which can also sense very-low attention from different analytes because the required analyte toward the gate terminal makes a modify in the drain to source current.

The main types of potentiometric biosensors are ISE or Ion-Selective Electrodes based on the membrane, ISFET (Ion-Selective Field Effect Transistors), Solid state devices, Screen-Printed Electrodes & modified electrodes through chemically like metal oxides otherwise electrodeposited polymers like sensitive layers.

Impedimetric Biosensor

The EIS (Electrochemical impedance spectroscopy) is a responsive indicator for a broad range of physical as well as chemical properties. A rising trend towards the expansion of Impedimetric biosensors is being presently observed. The techniques of Impedimetric have been executed to differentiate the invention of the biosensors as well as to examine the catalyzed responses of enzymes lectins, nucleic acids, receptors, whole cells, and antibodies.

Impedimetric Biosensors
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Voltammetric Biosensor

This communication is the base of a new voltammetric biosensor to notice acrylamide. This biosensor was built with a carbon glue electrode customized with Hb (hemoglobin), which includes four prostatic groups of the hem (Fe). This type of electrode shows a reversible oxidation or reduction procedure of Hb (Fe).

Physical Biosensor

In conditions of classification, physical biosensors are the most fundamental as well as broadly used sensors. The main ideas behind this categorization also happen from inspecting the human minds. As the general working method behind the intelligence of hearing, sight, touch is to react on the exterior physical stimuli, therefore any detecting device that offers a reaction to the physical possessions of the medium was named as a physical biosensor.

The physical biosensors are classified into two types namely piezoelectric biosensors and thermometric biosensors.

Piezoelectric Biosensors

These sensors are a collection of analytical devices which work on a law of “affinity interaction recording”. The platform of a piezoelectric is a sensor element that works on the law of oscillations transform due to a collection jump on the surface of a piezoelectric crystal. In this analysis, biosensors having their modified surface with an antigen or antibody, a molecularly stamped polymer, and heritable information. The declared detection parts are normally united by using nanoparticles.

Piezoelectric Biosensors
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Thermometric Biosensor

There are various types of biological reactions which are connected with the invention of heat, and this makes the base of thermometric biosensors. These sensors are usually named thermal biosensors

Thermometric Biosensor
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Thermometric-biosensor is used to measure or estimate serum cholesterol. As cholesterol obtains oxidized through the enzyme cholesterol oxidize, then the heat will be produced which can be calculated. Similarly, assessments of glucose, urea, uric acid, and penicillin G can be done with these biosensors.

Optical Biosensor

The Optical biosensor is a device that uses an optical measurement principle. They use fiber optics as well as optoelectronic transducers. The term optrode represents a compression of the two terms optical & electrode. These sensors mainly involve antibodies and enzymes like the transducing elements.

Optical Biosensor
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Optical biosensors permit a secure non-electrical inaccessible sensing of equipment. An extra benefit is that these frequently do not need reference sensors, because the comparative signal can be produced by using a similar light source to the sampling sensor. The optical biosensors are classified into two type’s namely direct optical detection biosensors and labeled optical detection biosensors.

Wearable Biosensors

The wearable biosensor is a digital device, used to wear on the human body in different wearable systems like smartwatches, smart shirts, tattoos which allows the levels of blood glucose, BP, the rate of heartbeat, etc

Wearable Biosensors
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Nowadays, we can notice that these sensors are carrying out a signal of improvement to the world. Their better use and ease can give an original level of experience into a patient’s real-time fitness status. This data accessibility will let superior clinical choices and will affect enhanced health results and extra capable use of health systems.

For human beings, these sensors may assist in premature recognition of health actions and prevention of hospitalization. The possibility of these sensors to reduce hospital stays and readmissions will definitely attract positive awareness in the upcoming future. As well, investigate information says that WBS will definitely carry cost-effective wearable health equipment to the world.

Enzyme Biosensor

This sensor is one kind of analytical device, used to merge an enzyme using a transducer to generate a signal that is proportional to the concentration of the target analyte. Further, this signal can be amplified, stored, processed for later analysis.

DNA Biosensor

The development of DNA biosensors can be done based on identification techniques of nucleic acid for analysis of simple, rapid & economical testing of genetic & infectious diseases. Also, the exact DNA series detection is important in several areas like food analysis, clinical, environmental, etc. For better detection techniques, SAM & SELEX technologies are used for developing better recognition techniques for DNA Biosensors.

Different from antibodies or enzymes, recognition of nucleic acid layers can be willingly created & regenerate for several uses.

As compared to normal hybridization, these sensors, as well as gene chips, have many benefits because of their enormous potential for attaining specific data in a simpler, cheaper & faster manner. Further, these sensors have been increased but, the fundamental investigation is still required to enhance the sensor technologies, detecting plans, instrumentations for analytical & procedures.

Immunosensors

Immuno sensors were recognized on the truth that antibodies include high affinity to their particular antigens like the antibodies particularly combine to toxins or pathogens or interact through host immune system’s components. These types of biosensors are based on affinity ligand solid-state devices where the reaction of immunochemical can be connected to a transducer.

Magnetic Biosensors

These types of sensors are used to gauge changes within magnetically persuaded effects or magnetic properties. These kinds of sensors use crystals or particles of super-paramagnetic otherwise paramagnetic to detect biological communications through measuring changes within magnetic properties like changes within coil inductance, resistance.

Resonant Biosensors

In a resonant biosensor, a transducer like an acoustic wave can be connected through a bio-element. Once the analyte molecule is connected toward the membrane, then the mass of the membrane alters. So, the final change within the mass subsequently alters the transducer’s resonant frequency. After that, the change in frequency can be measured.

Thermal Detection Biosensor

Thermal detection type biosensor uses one of the basic biological reaction properties like heat production or absorption and changes the temperature when the reaction occurs. The designing of this sensor can be done by uniting the molecules of an immobilized enzyme using temperature sensors. Once the analyte & the approaches in contact, then the enzyme’s heat reaction can be measured and & adjusted against the concentration of the analyte.

The whole heat generated otherwise absorbed can be proportional toward the molar enthalpy & the total number of molecules within the reaction. The temperature measurement is normally achieved through a thermistor known as enzyme thermistors. Thermistors are ideal in some applications as they are sensitive to thermal changes. Not like other types of transducers, thermal sensors do not require regular recalibration & they are insensible to the properties of electrochemical & optical of the sample. These sensors are used to detect pathogenic & pesticide bacteria.

Biosensors Applications

Biosensor devices include a biological element as well as a physiochemical detector and the main function of this device is to detect analytes. So, the applications of biosensors are in a wide range. These devices are applicable in the medical, food industry, the marine sector as they offer good sensitivity & stability as compared with the usual techniques. In recent years, these sensors have become very popular, and they are applicable in different fields which are mentioned below.

Applications of Biosensor
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  • Common healthcare checking
  • Metabolites Measurement
  • Screening for sickness
  • Insulin treatment
  • Clinical psychotherapy & diagnosis of disease
  • In Military
  • Agricultural, and Veterinary applications
  • Drug improvement, offense detection
  • Processing & monitoring in Industrial
  • Ecological pollution control
  • Diagnostic & Clinical
  • Industrial & Environmental Applications
  • Study & Interaction of Biomolecules
  • Development of Drug
  • Detection of Crime
  • Medical Diagnosis
  • Monitoring of Environmental Field
  • Quality Control
  • Process Control in Industries
  • Pharmaceuticals Manufacturer & Organs Replacement

Thus, biosensors are becoming gradually more complicated, mostly due to a blend of advances in two technological fields like biotechnology & microelectronics. These are highly important devices to measure an extensive spectrum of analytes like gases, organic compounds, bacteria & ions.

Thus, this is all about an overview of biosensors and the main components used in this sensor are physical components like amplifier & transducer whereas biological components like analyte & sensitive bio-element. The characteristics of biosensors mainly include Linearity, Sensitivity, Selectivity & Response Time.

From the above article, finally, we can conclude that biosensors and bioelectronics have been used in a lot of areas of healthcare, life science research, environmental, food & military applications. Further, these sensors can be enhanced as nanobiotechnology. The best example of the future use of nanobiotechnology includes electronic paper, contact lenses, and Nokia morph. Here is a question for you, what are wearable biosensors?

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