The purpose of a biosensor is the detection of biologically-relevant targets such as proteins, DNA, pathogens, cells, bacteria, pollutants, hormones and enzymes. In most cases, their presence and/or concentration in samples such as blood, urine, saliva, sweat or tears can be an early indicator of disease, so that the sensor can be used as a valuable diagnostic tool.
Biosensors are analytical devices that convert a biological response into an electrical signal. Biological sensors, or biosensors, may be defined as devices that probe the environment for specific molecules or entities through chemical, biochemical, or biological assays. The targets can be airborne, in liquids, or in solid materials.
Sensing systems generally consist of a recognition element (i.e., a detection element) and a transduction method to translate the recognition into an observable, quantifiable electronic or optical signal. One type of assay, known as an immunoassay, is commonly used to detect and identify biological agents, including bacteria, viruses, and proteins.
Biosensor components may have microscale features but may not necessarily be small scale. Ranging from several square centimeters to the size of a computer chip, a small sensor that can perform all of the functions normally carried out at the laboratory bench is sometimes referred to as a “laboratory on a chip.”
It is hard to overestimate the impact that biosensors would have—devices would acquire a new sense organ. And this is not merely a metaphor—major corporations are working on technologies to enable AI, intelligent gadgets, and biointerfaces that would serve as mediators between the human brain and computers. A combination of these technologies could give rise to real cybernetic organisms.
Biosensors and Biochips
In its general form, a biosensor is a transducer that reports a molecular or biochemical binding event as a physical quantity. In the case of a surface affinity biosensor, the sensing element is a surface covered in a biorecognition molecule such as DNA, proteins, antibodies or particular cell receptors that can selectively bind to targets in the analyte under examination. Depending on the transduction mechanism, biosensors can be classified into electrical, electrochemical, piezoelectric, nanomechanical, acoustic, magnetic or optical.
Applications of nanomaterials in biosensors provide opportunities for building up a new generation of biosensor technologies. Nanomaterials improve mechanical, electrochemical, optical and magnetic properties of biosensors and are developing towards single molecule biosensors with high throughput biosensor arrays.
Small-scale biosensing devices that incorporate biologically derived molecules that selectively capture specific target molecules are called biochips. Biochips use a biorecognition element, such as an antibody (protein) or oligonucleotide, as the reagent to selectively capture and thereby identify target molecules.
Biochips may be used in external applications (e.g., to analyze a sample of biological fluids) or in internal applications (e.g., invasive assays, in which devices are temporarily implanted or placed inside the human body). A good example of a biochip is a sensor placed under the skin for detecting blood glucose
Biological molecules possess special structures and functions, and determining how to fully use the structure and function of nanomaterials and biomolecules to fabricate single molecule multifunctional nanocomposites, nanofilms, and nanoelectrodes, is still a great challenge.
The processing, characterization, interface problems, availability of high quality nanomaterials, tailoring of nanomaterials, and the mechanisms governing the behaviour of these nanoscale composites on the surface of electrodes are also great challenges for the presently existing techniques. Ways to enhance the signal to noise ratio, how to enhance transduction and amplification of the signals, are also major impediments.
Team delivers world’s first biosensor chips based on copper and graphene oxide
Russian researchers from the Moscow Institute of Physics and Technology have developed biosensor chips of unprecedented sensitivity based on copper instead of gold. Biosensor chips are used by pharmaceutical companies to develop drugs. These chips are also indispensable for studying the kinetics of molecular interactions. Furthermore, they could serve as a basis for chemical analyzers used to find molecular markers of disease and to detect hazardous substances in food or the environment, including leaks from chemical plants, among other things.
The Russian research team from the Laboratory of Nanooptics and Plasmonics of MIPT’s Center for Photonics and 2-D Materials has developed a sensing chip based on unconventional materials: copper and graphene oxide. As a result, their device achieves unmatched sensitivity. Its configuration is mostly standard, and therefore compatible with existing commercial biosensors such as those from Biacore, Reichert, BioNavis and BiOptix.
“Our engineering solution is an important step toward developing biological sensors based on photonic and electronic technology,” says Valentyn Volkov, professor of the University of Southern Denmark, who also heads the Laboratory of Nanooptics and Plasmonics at MIPT. “By relying on standard manufacturing technologies and combining copper with graphene oxide—a material that has a great potential—we achieve a demonstrably high efficiency. This opens up new avenues for biosensor development.”
Nearly all commercial biosensor chips incorporate gold films several tens of nanometers thick—a nanometer is one billionth of a meter. The reason gold is so ubiquitous is that it has excellent optical properties and is chemically very stable. But gold is not perfect—it is expensive— over 25 times as expensive as high-purity copper. And gold is incompatible with the industrial processes used for manufacturing microelectronics, which severely limits its potential for application in device mass production.
Unlike gold, copper does not have these flaws. Its optical properties are on par with those of gold. Copper is used as an electrical conductor in microelectronics. However, it suffers from oxidation, or corrosion, and therefore has not been used in biochips. Now, MIPT researchers have solved this problem by covering the metal with a 10-nanometer dielectric layer. In addition to preventing oxidation, this altered the optical properties of the chip, making it more sensitive.
To further refine their biosensor design, the authors added a graphene oxide layer on top of the copper and dielectric films, enabling unprecedented sensitivity. In an earlier study, the authors used graphene oxide to increase the sensitivity of standard gold-based biosensors. The material proved to be beneficial for copper sensors as well.
Replacing gold with copper opens up the way for developing compact biosensing devices to be implemented in smartphones, portable gadgets, wearable devices, and smart clothes, because copper-based chips are compatible with conventional microelectronics technology. Globally, scientists and electronics industry giants such as IBM and Samsung are putting a lot of effort into creating compact biosensors that could be built into electronic devices analogous to present-day nano- and microelectromechanical accelerometers and gyroscopes.
The technologies proposed in this study could be used to create miniature sensors and neural interfaces, and that’s what we’re working on right now,” says Yury Stebunov, the lead author of the paper and co-founder and CEO of GrapheneTek LLC.
Biosensors can be used for military purposes at times of biological attacks. The main motive of such biosensors is be to sensitively and selectively identify organisms posing threat in virtually real time called biowarfare agents (BWAs) namely, bacteria (vegetative and spores), toxins and viruses. Several attempts to device such biosensors has been done using molecular techniques which are able to recognize the chemical markers of BWAs.
Most target threat molecules (e.g., chemical or biological warfare agents in liquid or aerosol form) are extremely difficult to detect. The concentrations of samples are very low, and the samples are likely to be “cluttered” with pollen, dust, and other natural biological constituents. The sensitivity of a biosensor also depends on the specific target molecule, some of which are more difficult to detect and assess than others.
Nucleic acid-based sensing systems are more sensitive than antibody-based detection methods as they provide gene-based specificity, without utilizing amplification steps to attain detection sensitivity to the required levels.
Small biosensing devices could change the way soldiers “see” the battlefield. Miniaturized, postage-stamp-sized biosensors containing biochips for monitoring the battlefield environment might be worn like wristwatches. In sufficient quantities, these inexpensive, miniature biosensors could provide hundreds of monitoring points for sensing target molecules.
A network of miniature biosensors carried by soldiers and vehicles deliberately placed throughout a likely battlefield could also have other Army applications. The presence of target threat molecules could provide advance knowledge of enemy presence, activities, or intentions. This biosensory intelligence could be combined with other sources of intelligence, thus providing commanders with new ways of seeing the battlefield and influencing the course of a battle.
US Military employing biosensors for enhancing soldiers perfromance
The US military is creating a new class of biosensors understand more about the soldiers who are using them and what is happening to their bodies at a molecular level when they fight. They could detect small changes in how alert, stressed or healthy the wearer is, according to the report by Defense One.
‘We want to set up a living laboratory where we can actually pervasively sense people, continuously, for a long period of time’, Justin Brooks, a scientist at the Army Research Lab told Defense One. ‘The goal is to do our best to quantify the person, the environment, and how the person is behaving in the environment.’ This might help them engineer conditions that dramatically improve a fighter’s performance.
According to the report, the US Air Force, Marine Corps, Navy and other special forces are looking to improve troops’ performance by looking at their bodies at a genetic level