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Another example, the potentiometric biosensor, (potential produced at zero current) gives a logarithmic response with a high dynamic range. Such biosensors are often made by screen printing the electrode patterns on a plastic substrate, coated with a conducting polymer and then some protein (enzyme or antibody) is attached.
3D Sarfus image of a DNA biochip. The microarray—the dense, two-dimensional grid of biosensors—is the critical component of a biochip platform. Typically, the sensors are deposited on a flat substrate, which may either be passive (e.g. silicon or glass) or active, the latter consisting of integrated electronics or micromechanical devices that perform or assist signal transduction.
Bio-FETs couple a transistor device with a bio-sensitive layer that can specifically detect bio-molecules such as nucleic acids and proteins. A Bio-FET system consists of a semiconducting field-effect transistor that acts as a transducer separated by an insulator layer (e.g. SiO 2) from the biological recognition element (e.g. receptors or probe molecules) which are selective to the target ...
A practical example of a label-based SPR-based miRNA biosensor is miR-21 detection with a LoD of 1 fM. The biosensor utilized graphene oxide–gold nanoparticles integrated with the sandwiching of the target miRNA between two DNA probes to amplify the SPR signal and have secondary hybridization through miR-21 report probes. [42]
In amperometric biosensors, an enzyme-catalyzed redox reaction causes a redox electron current that is measured by a working electrode. [11] Amperometric biosensors have been used in bio-MEMS for detection of glucose, galactose, lactose, urea, and cholesterol, as well as for applications in gas detection and DNA hybridization. [11]
Biosensors based on type of biotransducers. A biotransducer is the recognition-transduction component of a biosensor system. It consists of two intimately coupled parts; a bio-recognition layer and a physicochemical transducer, which acting together converts a biochemical signal to an electronic or optical signal.
Another example of genetic testing is gel electrophoresis. Gel electrophoresis uses DNA samples, along with biosensors to compare the DNA sequence of individuals. [40] Two other important instruments involved in genomic advances are microarray technology and DNA sequencing. Microarrays reveal the activated and repressed genes of an individual.
A number of paper-based biosensors have been developed, which use a variety of approaches. [5] In general, pathogens are detected via colorimetric, electrochemical, fluorescent, and chemiluminescent detection, though there are other types of sensors as well. [3] Several examples of paper-based biosensors are described below.