Biosensing has been one of the hottest topic attracting scientific minds since long. It is due to complex biological entities and are directly associated with the existence of a healthy environment. The design of biosensors also has gone through significant changes in the recent past. Biosensors are used for food quality estimation, environmental monitoring, and diagnosis of clinical and metabolic complications. Nanotechnology has involved some highly exciting ingredients for the improvement of sensing phenomenon. The use of nanomaterials is diversified ranging from nanoparticles, nanotubes, nanorods, and a nanowire has enhanced the speed of detection and its reproducibility in a significant better way. The unique properties of nanomaterials such as high electrical conductivity, better shock bearing ability, and the sensitive responses such as piezoelectric and versatile color based detection mechanisms are only the results of collection of nanomaterials properties.
The diagnostic Techniques with the help of Nano-Biotechnology has been adopted as research focal area. It encompasses the state of the art phenomenon of early diagnostics of viral disease HIV. This research work would entail a dedicated effort of the researcher (Ayesha Aslam) under the supervision of honorable and respected Supervisor (Sir, Dr. Hamid Manzoor).
1.1 Background to the Study
The development of efficient biosensors which can analyze the smallest details of the biological interactions even at a very small scale and with extreme precision and maximum ever possible sensitivities has played a vital role in diagnostic studies. A key component of the bio-sensing is the transduction mechanism which converts the bioanalyte interactions into an electrical form through the use of transduction mechanism. Nanomaterials can play a key role in this dimension because of its high surface area to volume ratios. Nanotechnology has brought about a great revolution in the domain of molecular biology which has provided an opportunity for manipulation of atoms and molecules and monitored the biological phenomenon at the physiological level with far greater precision.
2. Concept of Nanobiosensors
2.1 What is Biosensor and Nano-Biosensor ?
A biosensor can be defined as a sensing device or a measurement system designed specifically for estimation of a material by using the biological interactions and then assessing these interactions into a readable form with the help of a transduction and electromechanical interpretation. It comprises of three main components, namely, bio-receptor, transducer, and the detector. The main function or purpose of a biosensor is to sense a biologically specific material. Often, these materials are antibodies, proteins, enzymes, immunological molecules, and so on.
It is done by using another biologically sensitive material that takes part in the making of bioreceptor. So, a bioreceptor is that component of a biosensor which serves as a template for the material to be detected. There can be several materials which can be used as bioreceptors. For instance, an antibody is screened using antigen and vice versa; a protein is screened using its corresponding selective substrate and so on. The second component is the transducer system. The main function of this device is to convert the interaction of bioanalyte and its corresponding bioreceptor into an electrical form. The name itself defines the word as trans means change and ducer means energy. So, transducer basically converts one form of energy into another. The first form is biochemical in nature as it is generated by the specific interaction between the bioanalyte and bioreceptor while the second form is usually electrical in nature. This conversion of biochemical response into electrical signal is achieved through transducer. The third component is the detector system. This receives the electrical signal from the transducer component and amplifies it suitably so that the corresponding response can be read and studied properly.
2.2 Nanobiosensors: The Merging of Nanotechnology with Biosensors
Nanobiosensors are basically the sensors which are made up of nanomaterials and interestingly these are not the specialized sensors which can detect the nanoscale events and happenings. Nanomaterials are a unique gift of nanotechnology to the mankind; these are the materials which have one of their dimensions between 1 and 100 nanometers. The size of these materials makes them very special as they have most of their constituent atoms located at or near their surface and have all vital physiochemical properties highly different from the same materials at the bulk scale. They can play very efficient roles in the sensing mechanism of the biosensor technology. Integrated devices of the nanomaterials with electrical systems give rise to nanoelectromechanical systems (NEMS), which are very active in their electrical transduction mechanisms. Several nanomaterials have been explored on the basis of their properties. Some of such materials that are widely employed include nanotubes, nanowires, nanorods, nanoparticles, and thin films made up of nanocrystalline matter .
2.3 Selection and Optimization of Nanomaterials for Sensor Technology
There is a multitude, factors which govern or decide the use of a particular kind of nanomaterials for biosensing applications. we first focus on their desired manufacturing which is a part of experimental design known as ‘Nanofabrication.’ The technique of nanofabrication targets two vital operations, namely, the manufacturing and design of nanoscale adhesive surfaces via the technology of integrated circuits and the engineering of nanomaterial surfaces through the process of micromachining. NEMS technology has thus provided many materials with novel properties due to their nanoscale functionalization. NEMS and MEMS devices have enabled better and better sophisticated performance of the mechanical materials. In addition, these devices have been coupled with biological systems and molecules to improve their bio adhesion characteristics and the response to a wide range of stimuli. Another important factor considered while using nanomaterials for sensing application is the monitoring and optimization of their optical properties. In this way, nanomaterials, irrespective of their nature, need to be optimized for their performance and effect as per the desired goal before being actually implemented for the biosensing purpose.
2.4 Nanobiosensors: Variations and Types
The classification of nanobiosensors is based on the nature of nanomaterials incorporated in the biosensing operation. In the case of biosensors, we classify the sensors on two criteria, namely, the type of material to be analyzed and the other one is on the basis of signal transduction mechanism employed.
The criteria for classification of nanobiosensor are the nature of nano-material being used for improving the sensing mechanism. Nanobiosensors are called nanotube based sensors if they involve carbon nanotubes as enhancers of the reaction specificity and efficiency while biosensors using nanowires as charge transport and carriers are termed as nanowire biosensors. Some of the major classes of nanobiosensors are:-
2.4.1 Nanoparticle Based Sensors
126.96.36.199 Acoustic Wave Biosensors
Acoustic wave biosensors have been developed to amplify the sensing responses so as to improve the overall preciseness of the limits of biodetection. There can be so many stimulus based effects in these kinds of sensors.
188.8.131.52. Magnetic Biosensors
Magnetic biosensors utilize the specially designed magnetic nanoparticles. These are mostly ferrite based materials, either used individually or in combined form. These types of sensors are very useful with reference to the biomedical applications. Special devices such as superconducting quantum interference devices (SQUID) have been used for rapid detection of biological targets using the super paramagnetic nature of magnetic nanoparticles.
184.108.40.206. Electrochemical Biosensors
These sensors basically work to facilitate or analyze the biochemical reactions with the help of improved electrical means. These devices are mostly based on metallic nanoparticles. The chemical reactions between the biomolecules can be easily and efficiently carried out with the help of metallic nano-particles.
2.4.2 Nanotube Based Sensors
Carbon nanotubes are one of the most popular nanomaterials known right now in the world of material science and optoelectronic applications. Since their discovery in 1990’s, they have attracted interest worldwide because of their extraordinary properties.
2.4.3 Nanowire Based Sensors
Nanowires are cylindrical arrangements just like those of carbon nanotubes, having lengths in the order of few micrometers to centimeters and diameters within the nanorange. Nanowires are the one-dimensional nanostructures with very good electron transport properties
2.5 Applications of Nanobiosensors
Biosensors can be used for environmental monitoring of pollutants, toxicants, and physical aspects like humidity, heavy metal toxicity, and even presence of carcinogens.
2.5.1 Biomedical and Diagnostic Applications
Biosensors have been used for biological detection of serum antigens and carcinogens, and causative agents of so many metabolic disorders since time immemorial. The routine applications in diagnosis are best described by the use of biosensors in the detection of disorders like diabetes, cancer, allergic responses, and so many other disorders on the basis of serum analysis.
2.5.2. Environmental Applications
This is a relatively broader area of application. The detection of pollutants, toxic intermediates, heavy metals from waste streams and the monitoring of weather conditions like the estimation of humidity and many other vital features are really highly detailed and comprehensive tasks.
2.5.3. Miscellaneous Applications
Nanobiosensors can also be employed in the industrial operations, feeding of nutrient media and substrate mixtures into the bioreactors for diverse applications can be regulated using these sensors.
3. Research Objectives
‘ To find a functional model of Diagnostic design with the help of Nano-Technology.
‘ To find the new ways and innovations in early stage diagnostic of disease(HIV).
4. Methods and Tools
The researcher will primarily rely on quantitative method for the selection and analysis of Electro-chemical Biosensor – Protein IL-21(interleukin-21)
Interleukin -21 is the 1 class of cytokine. It is released by cd4 during the HIV infection. So It is used as a biomarker for early diagnosis. This biomarker merges with Gold nano-partical for fast response. This biomarker response through a heterodimeric receptor complex consists of IL-21 receptor and common gamma chain. Excellence receptor for this class is signature motif (WSXWS).It is involved in signal transduction .Sugar chain is an integral part of IL-21 receptor. Receptor chain consists of V shape. As human immunodeficiency virus inter into host body number of interleukin is reduced because this protein fight with virus. Number of interleukin -21 is directly proportion to the infection of the virus. The receptor of interlekin-21 has structural affinity with gold nano-partical. As we bind receptor with Nano material signal transduction mechanism. As we use electro chemical biosensor reaction takes place between Nano-material and protein. Receptor of the gamma chain is n-glycosylated.Thisglycosylated react with gold and gives fast response.