Medical technology is greatly improving and would soon enter the stage where we do not need to regularly inject insulin or use finger prick blood tests to monitor diabetes. The advancement in the field of biosensors will open up a whole lot of opportunities. One of them is the efficient monitoring of the blood sugar levels with a small sensor implanted under the skin. Such devices can also release insulin when needed and also communicate the details to a smartphone connected to them (Coleiro, 2013). Biosensors have not only its application in diabetes monitoring. It exhibits state of art applications in a number of medical and engineering fields such as tissue engineering, detection of pathogenic, imaging and physiologically relevant molecules in the body (Perumal & Hashim 2013).It also facilitates pharmaceutical industries, agriculture, environmental, food and beverages and many more others (Singh, Poshtiban & Evoy, 2013).
Biosensors as defined by Perumal & Hashim (2013) are analytical devices that use biological recognition system to target molecules or macromolecules. Hasan et al. (2014) defined biosensor as "a self-contained analytical device which combines a biological component with a physicochemical component for the detection of an analyte of biological importance." Hence, it is imperative to consider that the field of biosensor is evolving especially with its integration with nanotechnology that involving measurements at nano-scale.
There have been recent advances in diagnostics in the area of biosensors. Biosensors have long been used in medical diagnosis. Perumal & Hashim (2013) pointed out that antibodies based biosensors were applied for the first time to detection in the 1950s and this discovery made immuno-diagnosis possible. However, recently, a number of advances have been made in biosensors diagnostics. One of these advances emerged as the development of electrochemical biosensors. This involves the use of the electrode as the transduction element. It is defined as a self-contained integrated device which can provide specific qualitative or semi-qualitative information through a biochemical receptor indirect spatial contact with an electrochemical transduction element. This type of biosensor can be classified into four categories namely: amperometric, potentiometric, impedance and conductometric based on their various properties. Electrochemical biosensors can serve as immunosensors, DNA hybridization biosensors and molecularly imprinted polymer sensors (Barsan, Prathish, Sun & Brett, 2014; Perumal & Hashim, 2013).
Nano-biosensor is one of the most revolutionary aspects of biosensors in the recent time. Lots of researches are ongoing in order to develop effective nanotechnology-based biosensors. The studies identified the numerous applications of nanotechnology-based biosensors and diagnostics (NBBD) including (Carbon Nanotubes) CNTs, graphene, Quantum Dots (QDs), NPs and GNPs, Chitosan, Dendrimers and so forth. (Technical University of Liberec, 2013; Vashist, et al. 2012). These biosensors are useful in graphene-based biosensors such as graphene-based hydrogen peroxide biosensors, graphene-based cholesterol biosensor, and graphene-based glucose biosensor. In addition, it encompasses nonenzymatic biosensors; MEMS/NEMS based biosensors; carbon nanotube based biosensors and Quantum Dots based optical biosensors (Hasan et al., 2014; Wang, 2005). In tissue engineering, biosensors find huge applications. According to Hasan et al. (2014), some of the applications in this field include the detection of small molecules such as in monitoring blood glucose concentration to track diabetes. It holds the accurate and reliable measurement of hydrogen peroxide for clinical application and tissue engineering and in the measurement of adenosine triphosphate (ATP). It is also relevant in the detection of functional protein molecules and example of such molecules are bioenzymes. This is done in order to find out their characteristics for diagnostics, therapeutic and application in tissue engineering; Biosensors are also recently applied in the detection of other analytes. Different kinds of electrochemical biosensors are useful in achieving this goal. A typical example is amperometric biosensor that can detect the presence of E. coli indirectly and in detecting the presence of Salmonella directly. Biosensors have many other applications in tissue engineering and many other fields of study including bio-sensing (Hasanzadeh, Shadjou & Guardia, 2014). In addition, biosensors are in use for taste cell and associated signaling mechanism. Nanoparticle base compound provide amazing properties in manufacturing artificial devices for taste sensing (Wu et al., 2014).
The field of nanomedicine is an aspect that has attained much attention when it comes to biosensors. It is important to understand why nanotechnology is given so much attention since it was discovered. Nanotechnology came to be widely known after historical lecture delivered by the famous physicist and Nobel Laureate prize winner, Richard Feynman in 1959. During this lecture, he stated that there is plenty of room at the bottom (Vashist et al., 2012; LBB, 2009). Scientists soon identified how important nanotechnology was and how it can be used in manipulating atoms, synthesizing carbon molecules, addictive manufacturing, and many other applications (“Nanotechnology” , 2009).
Biosensor falls into the category of nanobiotechnology. LBB, (2009) defined nanobiotechnology as a field that brings together the design of new materials and devices with the designation of biological molecules, enzymes, and cells. The development of nanobiosensors is one of the most important applications of nanobiotechnology. Nanobiosensors are widely researched on for wider applications. For instance, Hasan et al. (2014) mentioned that there are recent advances in nanobiosensors technologies for applications in the monitoring of glucose concentrations so as efficiently to measure the blood glucose level in diabetes patients. They are also widely researched for use in combination with signaling and therapeutic delivery devices for in vivo screening and treatment. It appears that the nanotechnology has great prospect in biosensors and its applications. Gooding (2011) also stated that one of the two major areas where nanotechnology has significantly impacted biosensors research in the last few years is in the nanofabrication of biosensing interfaces. This ensures efficient fabrication of the surfaces and since nanotechnology typically involves addictive manufacturing. Hence, it is possible to manufacture miniature sized biosensing interfaces and also produce different kinds of designs as possible. The paper further pointed out that the rise of self-assembled monolayers (SAMs) is particularly essential in manufacturing biosensing interfaces. The SAMs accord manufacturers control in the molecular scale or level and therefore makes the manufacturing of biosensing interfaces much more effective. A lot of benefits are obtainable from the use of self-assembled monolayers. One of which is the production of biosensors with better performance. Not only this but also the technology helps in the development of new types of either sensitive or selective transduction mechanism in biosensors and some cases the resulting biosensors have both characteristics.
Solanki, Kim & Lee, (2008) studied stem cell imaging using nano-particles approach based on its characteristics of high spatial resolution and sensitivity. They found that nono probes are very effective in stem cell therapies like stem cell tracking with the help of nanoparticles. Micro-environmental signals hold good stem cell interaction and can be used to cope with challenges prevailing in regenerative medicine by developing improved pathway of signals. (Li et al., 2014; Solanki et al., 2008).
In the field of nanobiosensors, it is important to note that high surface area nanomaterials are very relevant. The benefits of such biosensors include the development of nanosensors that has shorter response time, improved sensitivity and are also compatible with in vivo biosensing. Obviously, nanotechnology offers biosensors a number of benefits. Vashist (2012) enlisted some most widely used nanomaterials in nano-based biosensors diagnostics (NBBD). CNTs based biosensors are one of these devices used in the detection of analytes in healthcare, industries, environmental monitoring, food sensing analysis, electrochemical sensing such as glucose monitoring and so forth. (Singh et al.,2013). Graphene is another promising material which have been widely researched and used for its properties. These properties include high thermal conductivity, high mechanical strength, adjustable optical properties and band gap. It holds high elasticity characteristics and high room temperature carbon mobility as well as displaying room temperature and quantum hall effect. This material is used in impedance, electrochemical, fluorescence and electrochemiluminescence biosensors to detect different kinds of analytes like hemoglobin, glucose, hydrogen peroxide gasses, catechol and so forth. Hasan et al. (2014) outlined that graphene-based biosensors are cheap having properties like good biocompatibility, large specific surface area and so forth. Other kinds of graphene-based biosensors include graphene quantum dot based biosensors, graphene-based glucose biosensor, graphene-based cholesterol biosensor and so forth; Quantum Dots are nanocrystals that have properties like high photochemical stability and broad excitation. They are widely used to develop optical biosensors to detect pharmaceutical analytes, biomolecules, and organic compounds. Other nanomaterials widely used in nano-based biosensors diagnostics include Nanoparticles (NPs) and Gold Nanoparticles (GNPs). They are used in developing immnoassays, diagnostics and biosensors for various analytes; Chitosan extensively used in biosensors and diagnostics and many others.
However, biosensors face a number of challenges that needs to be addressed for full integration of the technology. Biosensors are expected to find great applications in the medical field for diagnostic purposes in order to ensure successful treatment and recovery of patients suffering from different kinds of diseases. To make a biosensor compatible to achieve the purposes under consideration, it must be sensitive. In addition, this need to be built in a specific way to make it effective for detecting multiple biomarkers at low concentrations in biological fluids. To achieve this, there is a need of further development in biosensors (Gouvêa, 2014). As a matter of fact, biosensors should be further improved with enhanced effective features like multiple analysis of a number of biomarkers having tendency to develop arrays of sensors on the same chip.
Cancer testing is an important area in which biosensors find useful application. However, this aspect also faces challenges that need to be considered. Today, only few biosensors have been developed for cardiovascular and cancer-related testing. Problematically it is very difficult to utilize the potential of biosensors. This is simply because cancer is a very complex and diverse disease. As a matter of fact, for effective biosensor based cancer testing, it is important to ensure a continued development and validation of biomarkers as well as development of ligands for the biomarkers. In addition, it is necessary to continue the development of sample preparation methods as well as multi-channel biosensors that will be able to analyze many cancer markers at the same time.
For a wider application of biosensors in the future, it is very vital to improve the sensitivity of DNA biosensors for single-molecule detection in an unamplified sample. To achieve this, it will be important to improve on the signal-to-noise rate, improve the sensitivity of the traducers and also reduce background noise. This will call for ultrasensitive transducer technology.
Cost is another important aspect of biosensors that must be put strictly adjusted to make sure that the technology is widely accepted in the future. Besides cost, quality control of the devices must also be given precedence. To lower cost, it may be necessary to embrace homogeneous assay formats which will exclude sample preparation and amplification steps. More so, Gouvea (2014) found that the biosensor is a relatively new and innovative technology. Therefore, it faces a lot of limitations including cost considerations and some key technical barriers. These limitations must be overcome in order for biosensor to meet up with its future expectations. Furthermore, public acceptance is another factor that limits the wide application of nanotechnology in biosensors as well as other fields. Coleiro (2013) pointed out that the concern of the general public is hard to tackle because there are different views and opinions across different product types. Many people are happy that nanotechnology is used in some products while a number of other people are not. This is truly limiting nanotechnology application in biosensors.
Using nanotechnology for biosensors offers a number of benefits over conventional techniques. These advantages make biosensors surpass their disadvantages (Rai., Acharya. & Dey.2012). For instance, nanobiosensors have increased surface area to volume ratio. This ensures that the biosensor will have shorter response time, improved sensitivity and are also compatible with in vivo biosensing. In addition, studies have already shown that at the nano or atomic scale, materials show different properties and characteristics which would not be apparent at the ordinary scale or measurement, the same goes for nanobiosensors. At the atomic scale, nanobiosensors exhibit the highest level of efficiency and function with improved properties. The ultra- sensitivity of nanoparticles is a significant characteristic. This feature makes them quite better than conventional biosensors. Nanobiosensors are so sensitive that they can detect microorganisms like virus. They can even detect extremely low concentrations of substances that could cause harm in one way or the other. Conventional biosensors do not have such capability and therefore they are limited in a number of ways. As a result of the numerous features of nanobiosensors, Rai et al. (2012) stated that they possess great potential for application in varieties of fields. These fields are like environmental, bioprocess control, quality control of food, agriculture, biodefense and most importantly in the medical industry.
Tothill (2012) pointed out that if nanotechnology is utilized in biosensors, the resulting material produced has excellent advantages such as high precision and accuracy. The use of nanoparticles as labels ensures amplification of signals among many other benefits. This results to a number of advantages such as an increase in the sensitivity of the material produced and also multiplex sensor systems can be produced with this technology. Nanobiosensors also offer additional benefits such as high speeds, the smaller distance of travel by electrons, the lower power, and the lower voltage requirement to attain the same field in the semiconductor. They exhibit high component densities, improved chip functionality such as multi analysis capability and many more. The benefits offered by nanotechnology to biosensors cannot be overstated. However, the technology still demands improvement in order to meet the challenges of the future. Needless to say, a lot of researches are already going on in this field, and it is interesting to note that the technology will soon meet the demands of the various fields where it finds applications. (Guo, Porter, Youtie & Robinson, 2012; Huang, et al., 2012).
In short, biosensors are analytical devices that employ biological recognition systems to target molecules or macromolecules. They have gained attention over the years as a result of their wide application in different fields such as medicine, agriculture and so forth. Interestingly, nanotechnology finds great relevance in biosensors as it can be used in improving their features and qualities. Nanobiosensor is the name given to a biosensor that employs nanotechnology materials and technology.
Nanotechnology is simply a measurement at the nanoscale. It is imperative to consider that at such scale, materials exhibit a number of interesting characteristics compared to the normal scale. This feature has made the nanoscale an important field of study. At the nanoscale, biosensors exhibit exceptional characteristics such as increased surface area, efficiency, extreme high sensitivity and so forth. However, this technology is still limited in a number of ways because it is still in growing stage, and the sensitivity could be prone to error. Advancement in the technology is very important so as to meet up with the future demands. This essay took a look at the advances in biosensor diagnostics and also considered the impacts that biosensors will have in the field of nanomedicine. In addition, the future challenges of nanobiosensors as well as the advantages of nanobiosensors over conventional biosensors were thoroughly studied.
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