The term biosensor began to be used from 1977 when the first device was developed using living microorganisms immobilized on the surface of an ammonium-sensitive electrode.
A biosensor is an analytical device that transforms biological processes into electrical or optical signals, thus allowing the measurement of biological or chemical parameters.
They are constituted by a biological receptor, that detects a specific substance through biomolecular interactions, and a transducer, which interprets the reaction of recognition biological that produces the receiver translating them into a signal quantifiable.
As biological elements receivers can be used enzymes, antibodies, receptors proteícos, sequences of oligonucleotides, fragments subcellular as mitochondria, sections of animal and vegetable tissues, complete cells, etc. and as transducer optical devices, electrochemical, and mecano-acoustic, etc.
One of the main characteristics of these biosensors is its sensitivity and selectivity, as a result of the receiver and transducer being integrated. They can also perform the analysis of the substance to be determined in real time and in a direct way (without the need for a marker), unlike any biological or clinical analysis that always requires a marker (either colorimetric, fluorescent or radioactive).
These characteristics allow the biosensors to evaluate the variation over time of the processes, interpreting the fundamental mechanisms of these processes in real time.
Many biosensors also offer the advantages of their small size and great portability, allowing sample quantities to make the analysis relatively low (from micro to Nanolitres), which is very important if it is blood or DNA analysis, or if The sample is expensive or hard to get. To all this we must add that are cheaper to produce, have a time of long life and have a great versatility that allows the design of devices to the Charter.
Depending on the receptor used, biosensors can be classified in:
Electrochemical: Which determine electrical currents associated with electrons involved in redox processes, use selective electrodes for certain ions or determine Changes in conductance associated with changes in the ionic environment of solutions.
Thermometric: Which use thermistor devices capable of recording the small differences in temperature produced by biochemical reactions.
Piezoelectric: Where the variation of the resonance frequency of a piezoelectric crystal behaves linearly with the density of superficial mass deposited on it.
Optical: Where the immobilized biological component is an enzyme linked to a chromophore that when absorbed energy is excited to emit different colors.
Cellular: Which possess whole cells immobilized, respond to a wide spectrum of substrates.
Applications of Biosensors
One of the most used biosensors is the one that measures glucose in the blood. In fact, the first biosensor was a glucose analyzer developed by Clark and Lyons in 1962 and marketed. It uses an enzyme (receptor) that processes glucose molecules, releasing an electron for each molecule processed. This electron is collected in an electrode (transducer) and the flow of electrons is used as a measure of glucose concentration.
The goal is to implant it into a small living chip that is able to monitor patients in real time by means of a wireless connection. These objects outside our body are formed by an amalgam of living cells and electronic components.
Biosensors are also used to determine the organoleptic characteristics of food. In the case of fruits it is possible to analyze the content of some organic acids and sugars that are indicators of their maturity. In the wines, there are compounds that give rise to the appearance of unpleasant flavors and aromas such as the case of 2, 4, 6-Tricloroanisol, which is a compound of microbial origin related to the corks that cover the bottles.
Another amazing application is the bionic lenses, biosensors integrated into lenses that allow them to do a rapid diagnosis of our health through the retina or a HUD device (transparent display that shows the data without The user deflects the view to replace the environment that we see by an augmented reality…