Biosensor Principle

Introduction

A biosensor is a diagnostic device used for the detection of a physical or chemical substance that combines a biological component with a physio-chemical detector. The reader of the biosensor device connects with the signal processors or associated electronics, which are primarily responsible for the display of results in a user-friendly manner. Now it is possible to generate a user-friendly display that includes a transducer and sensitive elements.

There are primarily two types of biosensors, some are portable and others are either the fixed type or bench-type. Some examples are electrochemical, catalytic Bead, photoionization, infrared, infrared Image, ultrasonic, holographic detectors/sensors and more recently surface plasmon resonance (SPR) and magneto-optic (MO) surface plasmon resonance (MOSPR)-based sensors.

The major requirement of any biosensors depends on the approach in terms of commercial applications and research in the identification of the target molecule, as well as the availability of an appropriate biological recognition element.

The most common and best example of a commercial biosensor is the blood glucose biosensor. This sensor utilizes the glucose-oxidase enzyme that breaks down the glucose. In this process of breakdown, it first oxidizes glucose and uses two electrons to reduce the flavin adenine dinucleotide (FAD) — an enzyme component to FADH2 which is then oxidized by the electrode in several steps. The resulting current is a measure of the concentration of glucose. In this scenario, the electrode is the transducer, and the enzymes are the biologically active components.

Applications of Biosensors

Most optical biosensors are based on the principle of surface plasmon resonance (SPR). The SPR occurs when a thin layer of gold on a high refractive index glass surface absorbs the laser light and produces electron waves (known as surface plasmons) on the gold surface. This condition arises at a specific angle and wavelength of the incident light. The phenomena depend on the binding of a target analyte to a receptor that produces a measurable signal.

One way the SPR sensors operate is by using a sensor chip. The chip consists of a plastic cassette supporting a glass plate, coated with a microscopic layer of gold on one of the sides. This side is where the optical detection apparatus of the instrument lies. The opposite side of the plate is then attached to the microfluid flow system that allows the passage of reagents in the solution.

The glass sensor chip of this side can be modified in a number of ways, which allows easy attachment of molecules of interest. Hence, the refractive index at the flow side of the chip surface has a direct influence on the behavior of the light reflected off the sensor side. The flow side of the chip has an effect bonded on the refractive index of the material of interest and in this way, biological interactions are measured to a high degree of sensitivity. As a result, the refractive index of the medium changes near the surface when the biomolecules are attached to the surface and the angle of SPR varies as the function of this change.

Biological biosensors are designed from a genetically modified form of a native protein or enzyme. The protein is configured for the detection of a specific analyte and the ensuing signal is read with the help of detection instruments such as fluorometers or luminometers, to name a few. To read more about “Biosensors” Click Here.

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