11-12-2012, 05:38 PM
Biosensor:Novel Technique And Its Use
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ABSTRACT
Biosensor is a device which converts a biological response into an electrical signal whose amplitude depends on the concentration of the analyte taken in the solution. Electrochemical biosensor is a class of most widespread and mainly enzyme based which fascinate attention because of its unique properties. In this type of biosensor, biological material is combined with nanocrystalline material which provides high surface to volume ratio and also shows high surface activity. Reason of this study is that they preserve the enzyme activity. In present scenario ZnO is become centre of attraction in biosensing field not only because of its semiconducting or pyroelectric properties but also as shows biomimetic and high electron transfer features. It also has high Iso Electric points (IEP’S) which makes it more appropriate for the adsorption of proteins with low (IEP’s). Here we are destined to prepare a device which can rapidly determine the concentration of phenolic compound. Phenolic compounds are often exist in wastewater and cause many environmental problems thus sensitive monitoring of phenol should be done and more efforts are required and electrochemical detection is taken into consideration due to its low cost and easy operation. Tyrosinase is an enzyme which shows a IEP’S of 4.5 and exhibits well catalysing selectivity for detection of phenolic compound and is generally immbolised on ZnO because of ZnO has high IEP’S around 9.5. This immobilisation helps to design a phenol biosensor. In this way phenol biosensor developed based on the electrostatic attraction of ZnO and tyrosinase and it works in -0.2V. Biosensor had a fast response of under 5 s and the linear range of concentration spanned from 0.02 to 0.18 mM. The prepared biosensor had a similar response time below 5 s. There were two different ranges for the sensitivity and linear response and the KM value was as low as 0.17 μM.
Introduction
Biosensor is an analytical device that combines a transducer to produce a signal with a biologically sensitive and selective component. Biosensors can measure compounds present in the environment, chemical processes, food and human body at low cost if compared with traditional analytical techniques. These signal can result from a change in protons concentration, release or uptake of gases, light emission, absorption and so forth, brought about by the metabolism of the target compound by the biological recognition element. The transducer converts this biological signal into a measurable response such as current, potential or absorption of light through electrochemical or optical means, which can be further amplified, processed and stored for later analysis.
Biomolecules such as enzymes, antibodies, receptors, organelles and microorganisms as well as animal and plant cells or tissues have been used as biological sensing elements. Among these, enzymes offer advantages of ability to detect a wide range of chemical substances, and broad operating pH and temperature range, making them ideal as biological sensing materials. Enzymes have been integrated with a variety of transducers such as amperometric, potentiometric, calorimetric, conductimetric, colorimetric, luminescence and fluorescence to construct biosensor devices The purpose of this review is to highlight the advances in the developing area of enzymal biosensors with particular emphasis on the use of electrochemical properties of enzyme.
Exposure
Potential sources which are responsible for the phenol exposure include, the production and use of phenol and its products, cigarette smoke, the degradation of benzene under the influence of light, and the presence of phenol in liquid manure. Amount of phenol present in atmospheric levels are measured to be less than 1 ng/m3 urban/suburban atmospheric levels vary from 0.1 to 8 µg/m3, while concentrations near industry may be up to two orders of magnitude higher. Cigarette smoke and smoked food products are the main sources of phenol exposure
At normal environmental concentrations, phenols are unlikely to damage wildlife or plants. Man-made releases are usually to water bodies or soil, where they can persist (particularly if there is limited oxygen, such as in landfills or boggy water-logged soils). Some phenols can also accumulate in aquatic organisms. Due to the fact that they do not easily evaporate, phenols are not usually found at high concentrations in the atmosphere. Phenols are toxic to aquatic wildlife: effects vary according to the type of phenol in question. Some phenols (such as chlorophenols) persist and accumulate in the environment and may therefore have environmental effects at a global level.
ZnO-Based Enzyme Biosensing
Glucose
Glucose biosensor, as one of the most popular biosensors, has been intensively investigated due to its importance in clinics, environment and food industry. Glucose amperometric biosensor using glucose oxidase (GOD) as the enzyme is one of the most popular biosensors to be intensively investigated. Application of ZnO nanostructure in the glucose biosensors just appeared in the last several years. summarizes the state-of-the-art of ZnO utilization for enzyme immobilization in electrochemical biosensor platforms and their analytical performances. Physical adsorption is the mostly used method for enzyme immobilization. ZnO nanocomb, prepared by vapor-phase transport, was reported relatively early as a platform for glucose detection. During the manufacturing process for ZnO nanocombs , the temperature was controlled at 900 C. A mixture of ZnO and graphite powders was used as reaction raw material sources, and argon and oxygen were used as carrier gas and reaction gas, respectively. For enzyme immobilization, GOD was physically adsorbed onto the nanocomb modified Au electrode and covered by Nafion solution. The prepared biosensor had a diffusion-controlled electrochemical behavior and a fast response time, within 10 s. The value of K (Michaelis-Menten constant) was reported to be 2.19 mM. Using a similar technique, Weber et al. obtained ZnO nanowires with a typical length of 0.5–2 μm and a diameter of 40–120 nm , which were grown from the substrate with an array of ZnO nanowires . For the enzyme immobilization, physical adsorption was also adopted to immobilize GOD onto the electrode. Such a prepared biosensor had a wider linea range from 0.1 to 10 mM, compared to those of others .
H2O2
Over the past decades, the determination of hydrogen peroxide has been a very active study area because H O plays an important role in the food industry, environmental monitoring and clinical diagnosis. Electrochemical tracking of biological targets by way of enzyme-based H2O2 detection is of special interest. Comparing to other analytical techniques, such as spectrometry, titrimetry, and chemiluminescence , electrochemical enzyme biosensors have the advantages of high selectivity of the biological recognition elements and high sensitivity of electrochemical transduction process. H2O2 biosensors based on ZnO nanostructures using different approaches. A H O biosensor was developed using waxberrylike ZnO microstructures consisting of nanorods (8–10 nm) as a platform . These ZnO microstructures made by a wet chemical method possessed good biocompatibility without any damage to the secondary structure of the horseradish peroxidase (HRP) on the nano-ZnO/HRP electrode. Such ZnO nanomaterials with high surface areas could provide a platform for the reduction of H O by contributing excess electroactive sites and thus providing enhanced electrocatalytic activity. The transport characteristics of the electrode were controlled by the diffusion process. This kind of biosensor had a much wider linear range, from 0.l5 to 15 mM, and a detection limit of 0.115 μM. The modified electrode with carbon-decorated ZnO nanoarrays was also a good platform for H O development. At the potential of −0.4 V, the biosensor showed a high sensitivity of 237.8 μA/cm •mM and fast
Phenol
In this paper author is destined to produce the electrochemical biosensor for the monitoring of phenolic compound by utilising the properties of tyrosinase enzyme, an copper containing
enzyme having a isoelectric point around 4.5 which catalyse the reduction of molecular oxygen by taking electron donor from the electron donar i.e phenolic compound and oxidises the phenol into quinone and itself reduces to water. the corresponding quinone species can be electrochemically reduced to allow convenient low-potential detection of phenolic analyte. Experiment is performed in amperometric biosensor detector. Amperometric biosensor Coupled oxidoreductase and dehydrogenase enzyme reactions to electrodes There are three principal means by which amperometric biosensors are employed in analytical systems. For simplicity, let’s assume the common redox cross reaction
[attachment=43419]
ABSTRACT
Biosensor is a device which converts a biological response into an electrical signal whose amplitude depends on the concentration of the analyte taken in the solution. Electrochemical biosensor is a class of most widespread and mainly enzyme based which fascinate attention because of its unique properties. In this type of biosensor, biological material is combined with nanocrystalline material which provides high surface to volume ratio and also shows high surface activity. Reason of this study is that they preserve the enzyme activity. In present scenario ZnO is become centre of attraction in biosensing field not only because of its semiconducting or pyroelectric properties but also as shows biomimetic and high electron transfer features. It also has high Iso Electric points (IEP’S) which makes it more appropriate for the adsorption of proteins with low (IEP’s). Here we are destined to prepare a device which can rapidly determine the concentration of phenolic compound. Phenolic compounds are often exist in wastewater and cause many environmental problems thus sensitive monitoring of phenol should be done and more efforts are required and electrochemical detection is taken into consideration due to its low cost and easy operation. Tyrosinase is an enzyme which shows a IEP’S of 4.5 and exhibits well catalysing selectivity for detection of phenolic compound and is generally immbolised on ZnO because of ZnO has high IEP’S around 9.5. This immobilisation helps to design a phenol biosensor. In this way phenol biosensor developed based on the electrostatic attraction of ZnO and tyrosinase and it works in -0.2V. Biosensor had a fast response of under 5 s and the linear range of concentration spanned from 0.02 to 0.18 mM. The prepared biosensor had a similar response time below 5 s. There were two different ranges for the sensitivity and linear response and the KM value was as low as 0.17 μM.
Introduction
Biosensor is an analytical device that combines a transducer to produce a signal with a biologically sensitive and selective component. Biosensors can measure compounds present in the environment, chemical processes, food and human body at low cost if compared with traditional analytical techniques. These signal can result from a change in protons concentration, release or uptake of gases, light emission, absorption and so forth, brought about by the metabolism of the target compound by the biological recognition element. The transducer converts this biological signal into a measurable response such as current, potential or absorption of light through electrochemical or optical means, which can be further amplified, processed and stored for later analysis.
Biomolecules such as enzymes, antibodies, receptors, organelles and microorganisms as well as animal and plant cells or tissues have been used as biological sensing elements. Among these, enzymes offer advantages of ability to detect a wide range of chemical substances, and broad operating pH and temperature range, making them ideal as biological sensing materials. Enzymes have been integrated with a variety of transducers such as amperometric, potentiometric, calorimetric, conductimetric, colorimetric, luminescence and fluorescence to construct biosensor devices The purpose of this review is to highlight the advances in the developing area of enzymal biosensors with particular emphasis on the use of electrochemical properties of enzyme.
Exposure
Potential sources which are responsible for the phenol exposure include, the production and use of phenol and its products, cigarette smoke, the degradation of benzene under the influence of light, and the presence of phenol in liquid manure. Amount of phenol present in atmospheric levels are measured to be less than 1 ng/m3 urban/suburban atmospheric levels vary from 0.1 to 8 µg/m3, while concentrations near industry may be up to two orders of magnitude higher. Cigarette smoke and smoked food products are the main sources of phenol exposure
At normal environmental concentrations, phenols are unlikely to damage wildlife or plants. Man-made releases are usually to water bodies or soil, where they can persist (particularly if there is limited oxygen, such as in landfills or boggy water-logged soils). Some phenols can also accumulate in aquatic organisms. Due to the fact that they do not easily evaporate, phenols are not usually found at high concentrations in the atmosphere. Phenols are toxic to aquatic wildlife: effects vary according to the type of phenol in question. Some phenols (such as chlorophenols) persist and accumulate in the environment and may therefore have environmental effects at a global level.
ZnO-Based Enzyme Biosensing
Glucose
Glucose biosensor, as one of the most popular biosensors, has been intensively investigated due to its importance in clinics, environment and food industry. Glucose amperometric biosensor using glucose oxidase (GOD) as the enzyme is one of the most popular biosensors to be intensively investigated. Application of ZnO nanostructure in the glucose biosensors just appeared in the last several years. summarizes the state-of-the-art of ZnO utilization for enzyme immobilization in electrochemical biosensor platforms and their analytical performances. Physical adsorption is the mostly used method for enzyme immobilization. ZnO nanocomb, prepared by vapor-phase transport, was reported relatively early as a platform for glucose detection. During the manufacturing process for ZnO nanocombs , the temperature was controlled at 900 C. A mixture of ZnO and graphite powders was used as reaction raw material sources, and argon and oxygen were used as carrier gas and reaction gas, respectively. For enzyme immobilization, GOD was physically adsorbed onto the nanocomb modified Au electrode and covered by Nafion solution. The prepared biosensor had a diffusion-controlled electrochemical behavior and a fast response time, within 10 s. The value of K (Michaelis-Menten constant) was reported to be 2.19 mM. Using a similar technique, Weber et al. obtained ZnO nanowires with a typical length of 0.5–2 μm and a diameter of 40–120 nm , which were grown from the substrate with an array of ZnO nanowires . For the enzyme immobilization, physical adsorption was also adopted to immobilize GOD onto the electrode. Such a prepared biosensor had a wider linea range from 0.1 to 10 mM, compared to those of others .
H2O2
Over the past decades, the determination of hydrogen peroxide has been a very active study area because H O plays an important role in the food industry, environmental monitoring and clinical diagnosis. Electrochemical tracking of biological targets by way of enzyme-based H2O2 detection is of special interest. Comparing to other analytical techniques, such as spectrometry, titrimetry, and chemiluminescence , electrochemical enzyme biosensors have the advantages of high selectivity of the biological recognition elements and high sensitivity of electrochemical transduction process. H2O2 biosensors based on ZnO nanostructures using different approaches. A H O biosensor was developed using waxberrylike ZnO microstructures consisting of nanorods (8–10 nm) as a platform . These ZnO microstructures made by a wet chemical method possessed good biocompatibility without any damage to the secondary structure of the horseradish peroxidase (HRP) on the nano-ZnO/HRP electrode. Such ZnO nanomaterials with high surface areas could provide a platform for the reduction of H O by contributing excess electroactive sites and thus providing enhanced electrocatalytic activity. The transport characteristics of the electrode were controlled by the diffusion process. This kind of biosensor had a much wider linear range, from 0.l5 to 15 mM, and a detection limit of 0.115 μM. The modified electrode with carbon-decorated ZnO nanoarrays was also a good platform for H O development. At the potential of −0.4 V, the biosensor showed a high sensitivity of 237.8 μA/cm •mM and fast
Phenol
In this paper author is destined to produce the electrochemical biosensor for the monitoring of phenolic compound by utilising the properties of tyrosinase enzyme, an copper containing
enzyme having a isoelectric point around 4.5 which catalyse the reduction of molecular oxygen by taking electron donor from the electron donar i.e phenolic compound and oxidises the phenol into quinone and itself reduces to water. the corresponding quinone species can be electrochemically reduced to allow convenient low-potential detection of phenolic analyte. Experiment is performed in amperometric biosensor detector. Amperometric biosensor Coupled oxidoreductase and dehydrogenase enzyme reactions to electrodes There are three principal means by which amperometric biosensors are employed in analytical systems. For simplicity, let’s assume the common redox cross reaction