A gene based biosensor is used to monitor and optimize bioremediation of some of the complex chemicals such as polycyclic aromatic hydrocarbons (PAHs), benzene, toluene and also carcinogens. A university researcher is testing the effectiveness of genetically engineered Pseudomonas fluorescens in degrading the contaminant polycyclic aromatic hydrocarbons. A gene responsible for bioluminescence has been fused with the particular bacterial genes coding for enzymes that degrade the contaminants known as polycyclic aromatic hydrocarbons. It is believed that as the contaminant polycyclic aromatic hydrocarbons are degraded, the bacteria will produce the light and the quantity of PAH degradation can be identified using fiber-optics.
In immunosensors light is used to detect cancer causing agents or carcinogens in groundwater. Therefore these sensors are attached to the end of an optical fiber an antibody that specifically reacts with the carcinogenic agent, such as benzo(a)pyrene (BaP). That is anti-BaP antibody on the end of the fiber was immersed in a groundwater sample. The antibody was allowed to bind with the specific antigen that is BaP, if it is present in the groundwater sample. The antibody and antigen reaction product gives out light if illuminated by light of a particular wavelength. Therefore correct wavelength light was aimed through the fiber in the sample of groundwater. After 5 to 10 minutes, the product of this reaction is fluoresced, and then this fluorescence was transmitted back to the fiber, then it is measured.
Medical telesensors have got a small sensor attached to their body, which helps in detecting the temperature constantly and transmits data to the medical centre. Medical telesensors can also be used to detect blood pressure.
Research is going on to develop a chip, which can be used to measure blood oxygen level. As the blood oxygen level changes, the color of haemoglobin present in the blood is also altered. This chip will have a light source and also light detector that could measure changes in the color of haemoglobin and this in turn will help in detecting the blood oxygen level.
Bioreporter is an example for a biosensor based on detection of light emitted by specially genetically engineered microorganisms that is involved in bioremediation. However, in this case the light is originated from a particular protein that has been genetically engineered and inserted in certain bacteria. For example, the gene coding for luciferase is placed in the operon that codes for specific enzymes, which help in degrading unwanted chemical compounds such as toluene, organic solvent or other compounds. When these genetically engineered bacteria are metabolizing the toluene, the operon or genetic control mechanism also turns on the synthesis of the specific enzyme known as luciferase, which produces light in the presence of oxygen molecule.
Biochips are new generation of biosensors, designed using DNA probes. Probe recognition is done based on the principle of molecular hybridization process, which involves the joining of complementary sequences present in the strands of nucleic acid. These DNA probes are directly immobilized on optical transducers which allow detection of labelled probes by Raman or fluorescent method.
DNA biosensors have got many important applications in areas involved with nucleic acid identification. This kind of DNA probes can be used in detecting genetic diseases and also can be used in diagnosing genetic susceptibility towards a particular kind of disease. The biochip using antibody probes are recently developed to detect p53 proteins in an individual.
Application of Biosensors:
1. Biosensor fiber coated with specific antibody which recognizes L. Monocytogens are designed. When these biosensors are placed in liquid food solution, if any L. monocytogenns are present in the food sample, then they stick to the fiber. The presence of L.monocytogens is confirmed by adding secondary antibody. This secondary antibody should recognize L. Monocytogens and also it should produce fluorescent glow in the presence of laser light. This secondary antibody acts as a signalling molecule which indicates the presence of pathogen in the food sample.
2. Biosensors are also used in the detection of Staphylococcal enterotoxin
3. Biosensors are also used in detecting the pollutants. If pollutants are present in any sample then they attach to the sensor fiber and then they can be detected by using one of the methods like radioactivity, fluorescence or any color change.
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