Biosensor Term Paper New0

7/28/2019 Biosensor Term Paper New0

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AMITY INSTITUTE OF BIOTECHNOLOGY

AMITY UNIVERSITY

UTTAR PRADESH

Term paper on-Biosensors and theirapplications for the partial fulfillment ofBsc.

(Hons) Medical Biotechnology

Batch: 2007-2011

Year of submission-2008

Submitted to- Submitted by-

Tuhin Rashmi Mam Sangat Kochar

Roll No:-

BMB/07/114


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CERTIFICATE

This is to certify that the term paperon topic-Biosensors and theirapplications is the original workdone by Sangat Singh Kocharof Bsc.(hons) medical biotech under mysupervision and guidance.I hereby also certify that this work iscompletely genuine and is not copiedfrom anywhere.

Date- Tuhin Rashmimam

LecturerAmity

institute of biotechnology


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ACKNOWLEDGEMENT

I express my heartfelt gratitude to my

teacherTuhin Rashmi Mam who despite her busyschedule guided and supervised my termpaper on biosensors and theirapplications very efficiently. I am verythankful to her for sparing her precioustime and sharing even more precious

knowledge, without which thecompletion of this term paper would nothave been possible.I would also like to thank Prof. A.K.Shrivastava, The Director of AmityInstitute of Biotechnology for offering methis opportunity to present my

capabilities by means of this term paper.Last, but not the least I am very thankfulto my parents and my friends whosupported and encouraged me at everypoint of preparation of this term paper.

Sangat Singh Kochar2nd year- Bsc (hons) MedicalBiotechRoll no-114

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BIOSENSORS & THEIR APPLICATIONS-

INDEX: page no.

(1.) Introduction to biosensors 5

(2.) Review of literature 7

(3.) Components and working of a biosensor- 9a) A biological sensing element

b) A transducer

c) A signal conditioner or amplifier

d) A data processor

e) A signal generator

(4.)Generations of biosensors- 11a) First generation

b) Second generation

c) Third generation

(5.)Principles of detection or Types of biosensors- 14a) Calorimetric biosensor

b) Potentiometric biosensorc) Amperometric biosensor

d) Piezoelectric biosensor

e) Optical biosensor

f) Immunochemical biosensor

(6.)Applications 29

(7.)Conclusion 34

(8.) Summary 36

(9.) References 38

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(1.)Introduction to biosensors :

A biosensor is a device that detects, records, and transmits information regarding a

physiological change or the presence of various chemical or biological materials in

the environment.

A biosensor is an analytical device which employs a biological material to

specifically interact with an analyte. This interaction produces some detectable

physical change which is measured and converted into an electric signal by a

transducer. Finally, the electrical signal is amplified, interpreted and displayed as

analyte concentration in the solution or preparation.

An analyte is a compound whose concentration is to be determined, in this case by a

biosensor. The biological material used are usually enzymes, but nucleic acids,

antibodies, lectins, whole cells, entire organs or tissue slices are also used .

The nature of interaction between the analyte and the biological material used in

biosensor may be of two types:-

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(i) The analyte may be converted into a new chemical molecule by enzyme;

such biosensors are called catalytic biosensor.

(ii) The analyte may simply bind to the biological material present on the

biosensor. E.g.-to antibodies, nucleic acid; these biosensors are known as

affinity biosensors.

Recently, arrays of many different detector molecules have been applied in so called

electronic nose devices, where the pattern of response from the detectors is used to

fingerprint a substance. Current commercial electronic noses, however, do not use

biological elements.

Biosensors are already of major commercial importance, and their significance is

likely to increase as the technology develops. This is because they can be made to

respond specifically and with high sensitivity to a wide range of molecules, including

those of industrial, clinical and environmental importance. The best developed

systems are undoubtedly within the field of clinical medicine, where glucose

responsive biosensors play a vital role in the measurement of blood glucose that is

necessary for the management of diabetes.

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(2.) Review of literature-

In 2005 Li Q & Yuan J developed the Portable Blood Glucose Meter for Self-

monitoring of Blood Glucose enabling the patients with diabetes to detect bloodglucose with a glucose oxidase electrode independently at home.(1)

In 2006 Rodriguez-Mozaz S made a multi-analyte biosensor for fast and

simultaneous monitoring of organic pollutantssuch aspesticides atrazine, isoproturon

and the estrogen estrone in a drinking water treatment plant.(2)

In 2006 Liu X, Sun Y used enhanced optical immuosensor based on surface

plasmon resonance for determination of transferrin.(3)

In 2007 Skottrup P, Nicolaisen Mpresented a surface plasmon resonance

immunosensor for rapid determination of Phytophthora infestans sporangia a late

blight disease in potato.(4)

In 2008 Justesen AF said that antibody based sensors can be used to detect on site

pathogen in food.(5)

In 2008 Miyashita M, Ito N developed a urine glucose meter based on micro-planer

amperometric biosensor for self-monitoring of urine glucose.(6)

In 2008Ly SY, Cho NS made bovine IgG DNA-linked carbon nanotube biosensor

for Diagnosis of human hepatitis B virus.(7)

In 2008 Liang R, Jiang roduceJ introduced an improved amperometric glucose

biosensor that was constructed by immobilizing glucose oxidase (GOD) in a titania

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sol-gel film, and was prepared by a vapor deposition method, on a Prussian Blue

(PB)-modified electrode.(8)

In 2008 Sanz V, Mateos E launched a reagentless optical biosensors for organic

compounds based on auto-indicating proteins thus avoiding the use of chemical

fluorophores.(9)

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(3.) Components & working of

Biosensor-

A typical biosensor consists of the following five parts-

(a) The Biological Component:

It can be tissue, microorganisms, organelles, cell receptors, enzymes, antibodies,

nucleic acids, etc), a biologically derived material or biomimic).The sensitive

elements can even be created by biological engineering. It performs two key

functions-(i) it specifically recognizes the analyte, and (ii) interacts with it in such a

manner which produces some physical change detectable by the transducer. Due to

these features the biosensor is selective and sensitive. The biomaterial is suitably

immobilised onto the transducer.

For example, enzymes are usually immobilised by glutaraldehyde on a porous sheet

like lens tissue paper or nylon net fabric; the enzyme so produced is affixed to the

transducer. Correct immobilization of enzyme enhances their stability, which is

required in some cases. As a result, many enzyme immobilised systems can be used

more than 10,000 times over a period of several months.

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(b) The Transducer:

It determines the catalytic reaction and converts it to an electrical signal. The

transducer makes use of a physical or chemical change accompanying the reaction.

This may be-

(i) The heat output by the reaction (as in calorimetric biosensor)

(ii) Changes in distribution of charges causing an electric potential to be produced (as

in potentiometric biosensor)

(iii) Movement of electrons produced in redox reaction (as in amperometric

biosensor)

(iv) Light output driving the reaction or light absorbance difference between the

reactants and products.(as in optical biosensor)

(v) Effects due to the mass of the reactants or products (as in piezoelectric biosensor)

(vi) Direct detection of antigen bound to antibody coated surface of biosensor (as in

immunochemical biosensor)

(c) The Amplifier :

Also known as signal conditioner, it is an electrical device that amplifies the output

from the transducer. This is essential because the responses from the transducer must

be first converted to usable form by the user.

(d) The Data Processor:

It is the most important parts of a biosensor. The electrical signal from the amplifier

is often superimposed upon a relatively high and noisy baseline. The signal

processing normally involves subtracting a reference baseline signal, derived from

similar transducer without any biocatalytic membrane, from the sample signal,

amplifying the resultant signal difference and smoothing out the unwanted signal

noise.

(e) The Signal Generator:

The amplified and processed signal is finally displayed here. Thus, biosensors

convert a chemical information flow into an electrical information flow.

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(4.)Generations of biosensors-

Biosensors may be categorized as first, second, or third generation instrumentsaccording to the degree of intimacy between the biocatalyst and transducer. There are

three generations of biosensors-

First generation biosensors-

In first generation, the instruments of the two components (biocatalysts and

transducer) may be easily separated and both may remain functional in the absence of

the other.

The biocatalyst within a biosensor responds to the substrates in solution by catalyzing

a reaction. For e.g.-Glucose oxidase will catalyze the reaction-

Glucose + O2 gluconic acid + H2O2

By the use of first generation technology, the rate of this reaction can be measured as

follows-

(i) The rate of consumption of the substrate O2can be measured by its reduction at a

platinum cathode polarized at -0.6 V versus the standard calomel electrode i.e. with a

Clark oxygen electrode.

(ii) The rate of production of the productH2O2 can be measuredbyits oxidationat a

platinum anode polarized at +0.7 V versus the standard calomel electrode.

(iii) The rate of production of the product gluconic acid can be measured using a pH

electrode to measure the associated decrease in pH.

Table - EXAMPLE OF BIOSENSOR

Analyte Biocatalyst Transducer Immobilization

Stab

ility

Response

time

AlcoholAlcohol

oxidaseO2 Glutaraldehyde

>2

week

s

1-2 minute

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Second generation biosensors -

In these generation instruments, the biocatalyst and the transducer work in a more

intimate contact and the removal of any one affects the usual working of the other.

There are many ways in which the degree of intimacy between the two components

can be increased. Using oxidoreductases, the instruments can be constructed by

utilizing an electrode surface that is capable of capturing electrons, which are usually

transferred in the redox reactions.

A good example of a commercially available 2 nd generation instrument is blood

glucose meter. In this device the rate of oxidation of glucose is not measured by the

rate of disappearance of substrate or appearance of product, but by the rate of electron

flow from glucose of an electrode surface. The reactions that occur in this device can

be summarized as

Glucose + GO/FAD gluconic acid + GO/FADH2

(Red) (Ox) (Ox) (Red)

GO/FADH2 + 2M+ GO/FAD + 2M + 2H

(Red) (Ox) (Ox) (Red)

2M 2M+ + 2e

where GO/FAD represents the FAD redox centre of glucose oxidase in its oxidized

form, GO/FADH2 represents the FAD redox centre of oxidase in its reduced form,

and M is a mediator, which in case of glucose meter is ferrocene. The electrons

donated to the electrode surface then go to form a current that is proportional to the

rate of oxidation of glucose, and hence proportional to glucose concentration in the

blood.

Devices of this type are far more suitable for miniaturization. while the size of blood

glucose meter is that of a pen , devices using similar technology are now beingproduced that are so small they can be implanted under the skin to produce a blood

glucose measuring system in-situ .

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Third generation biosensors-

In 3rd generation instruments the biochemistry and electrochemistry are even more

closely linked and where the electrochemistry occurs at a semiconductor. The term

biochips may be applied to describe such instruments.

Such instruments are mostly at the research level, rather than commercial

development. They involve the most intimate interactions of the biocatalyst and the

transducer.

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(5.) Types of biosensors-(Principles of detection)

(a) Calorimetric biosensor-

Many enzyme catalyzed reactions are exothermic, generating heat, which may be

used as a basis for measuring the rate of reaction and, hence, the analyte

concentration. Such type of biosensor working on the basis of thermometry and

calorimetry is known as calorimetric biosensor. The diagram of a calorimetric

biosensor is shown below.

The sample stream (a) passes through the outer insulated box (b) to the heat

exchanger (c), within aluminum block (d). From here it flows past the reference

thermistor (e) and into the packed bed bioreactor (1 ml volume), containing the

biocatalyst, where the reaction occurs. The change in temperature is determined by

the thermistor(g) and the solution is passed to the waste (h). External electronics (i)

determines the difference in the resistance, and hence temperature, between the

thermistors.

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The temperature changes are usually determined by means of thermistors at the

entrance and exit of small packed bed columns containing immobilized enzymes

within a constant temperature environment. Under such closely controlled conditions,

up to 80% of the heat generated in the reaction may be recorded as a temperature

change in the sample. This may be simply calculated from the enthalpy change and

the amount reacted.

Principle-

If a 1 mM reactant is completely converted to product in a reaction generating 100 kJ

mole-1 then each ml of solution generates 0.1 J of heat. At 80% efficiency, this will

cause a change in temperature of the solution amounting to approximately 0.02C.

This is about the temperature change commonly encountered and necessitates a

temperature resolution of 0.0001C for the biosensor to be generally useful. Hence it

follows following relation-

(dR/R) = (-B/T12) (dT).

The relative decrease in the electrical resistance (dR/R) of the thermistor is

proportional to the increase in temperature (dT). A typical proportionality constant (-

B/T12) is -4%C-1. The resistance change is converted to a proportional voltage

change, using a balanced Wheatstone bridge incorporating precision wire-wound

resistor, before amplification.

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(b) Potentiometric biosensor-

Potentiometric biosensors make use of ion-selective electrodes in order to transduce

the biological reaction into an electrical signal. In the simplest terms this consists of

an immobilised enzyme membrane surrounding the probe from a pH-meter , where

the catalysed reaction generates or absorbs hydrogen ions . The reaction occurring

next to the thin sensing glass membrane causes a change in pH which may be read

directly from the pH-meter's display.

Figure- A simple potentiometric biosensor. A semi-permeable membrane (a)

surrounds the biocatalyst (b) entrapped next to the active glass membrane (c) of a pH

probe (d). The electrical potential (e) is generated between the internal Ag/AgCl

electrode (f) bathed in dilute HCl (g) and an external reference electrode.

There are three types of ion-selective electrodes which are of use in biosensors:

o Glass electrodes for cations (e.g. normal pH electrodes) in which the sensing

element is a very thin hydrated glass membrane which generates a transverseelectrical potential due to the concentration-dependent competition between the

cations for specific binding sites. The selectivity of this membrane is determined

by the composition of the glass. The sensitivity to H+ is greater than that

achievable for NH4+.

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o Glass pH electrodes coated with a gas-permeable membrane selective for CO 2,

NH3 or H2S. The diffusion of the gas through this membrane causes a change in

pH of a sensing solution between the membrane and the electrode which is then

determined.

o Solid-state electrodes where the glass membrane is replaced by a thin membrane

of a specific ion conductor made from a mixture of silver sulphide and a silver

halide. The iodide electrode is useful for the determination of I - in the peroxidase

reaction and also responds to cyanide ions.

Principle-

The response of an ion-selective electrode is given by

where E is the measured potential (in volts), E0 is a characteristic constant for the ion-

selective/external electrode system, R is the gas constant, T is the absolute

temperature (K), z is the signed ionic charge, F is the Faraday, and [i] is the

concentration of the free uncomplexed ionic species .

This means that there is an increase in the electrical potential of 59 mv for every

decade increase in the concentration of H+ at 25C. The logarithmic dependence of

the potential on the ionic concentration is responsible both for the wide analytical

range and the low accuracy and precision of these sensors. Their normal range of

detection is 10-4 - 10-2 M, although a minority are ten-fold more sensitive. Typical

response time are between one and five minutes allowing up to 30 analyses every

hour.

Biosensors which involve H+ release or utilisation necessitate the use of very weakly

buffered solutions (i.e. < 5 mM) if a significant change in potential is to be

determined.

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(c) Amperometric biosensor-

Amperometric biosensors function by the production of a current when a potential is

applied between two electrodes, the magnitude of current being proportional to thesubstrate concentration.

They generally have response times, dynamic ranges and sensitivities similar to the

potentiometric sensors. The simplest amperometric biosensors in common usage

involve the Clark oxygen electrode.

This consists of a platinum cathode at which oxygen is reduced and a silver/silver

chloride reference electrode. When a potential of -0.6 V, relative to the Ag/AgCl

electrode is applied to the platinum cathode, a current proportional to the oxygen

concentration is produced. Normally both electrodes are bathed in a solution of

saturated potassium chloride and separated from the bulk solution by an oxygen-

permeable plastic membrane (e.g. Teflon, polytetrafluoroethylene). The following

reactions occur-

Ag anode 4Ag0 + 4Cl- 4AgCl + 4e-

Pt cathode O2 + 4H+ + 4e- 2H2O

The efficient reduction of oxygen at the surface of the cathode causes the oxygen

concentration there to be effectively zero. The rate of this electrochemical reduction

therefore depends on the rate of diffusion of the oxygen from the bulk solution, which

is dependent on the concentration gradient and hence the bulk oxygen concentration.

It is clear that a small, but significant, proportion of the oxygen present in the bulk is

consumed by this process; the oxygen electrode measuring the rate of a process

which is far from equilibrium, whereas ion-selective electrodes are used close to

equilibrium conditions. This causes the oxygen electrode to be much more sensitive

to changes in the temperature than potentiometric sensors. A typical application for

this simple type of biosensor is the determination of glucose concentrations by the

use of an immobilised glucose oxidase membrane. The reaction results in a reduction

of the oxygen concentration as it diffuses through the biocatalytic membrane to the

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cathode, this being detected by a reduction in the current between the electrodes.

Other oxidases may be used in a similar manner for the analysis of their substrates

(e.g. alcohol oxidase, D- and L-amino acid oxidases, cholesterol oxidase, galactose

oxidase, and urate oxidase)

Figure- Schematic diagram of a simple amperometric biosensor. A potential is

applied between the central platinum cathode and the annular silver anode. This

generates a current (I) which is carried between the electrodes by means of a

saturated solution of KCl. This electrode compartment is separated from the

biocatalyst (here shown glucose oxidase, GOD) by a thin plastic membrane,

permeable only to oxygen. The analyte solution is separated from the biocatalyst by

another membrane, permeable to the substrate(s) and product(s). This biosensor is

normally about 1 cm in diameter but has been scaled down to 0.25 mm diameter

using a Pt wire cathode within a silver plated steel needle anode and utilizing dip-

coated membranes.

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Principle- The current (i) produced by such amperometric biosensors is related to the

rate of reaction (vA) by the expression:

i = nFAvA

Where, n represents the number of electrons transferred, A is the electrode area, and

F is the Faraday. Usually the rate of reaction is made diffusionally controlled by use

of external membranes. Under these circumstances the electric current produced is

proportional to the analyte concentration and independent both of the enzyme and

electrochemical kinetics.

The major problem with these biosensors is their dependence on the dissolved

oxygen concentration. This may be overcome by the use of 'mediators' which

transfer the electrons directly to the electrode bypassing the reduction of the oxygen

co-substrate. In order to be generally applicable these mediators must possess a

number of useful properties.

1. They must react rapidly with the reduced form of the enzyme.

2. They must be sufficiently soluble, in both the oxidised and reduced forms, to

be able to rapidly diffuse between the active site of the enzyme and the electrode

surface. This solubility should, however, not be so great as to cause significant

loss of the mediator from the biosensor's microenvironment to the bulk of the

solution. However soluble, the mediator should generally be non-toxic.

3. The overpotential for the regeneration of the oxidised mediator, at the electrode,

should be low and independent of pH.

4. The reduced form of the mediator should not readily react with oxygen.

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Mediators-The ferrocenes represent a commonly used family of mediators. Their

reactions may be represented as follows-

Electrodes have now been developed which can remove the electrons directly from

the reduced enzymes, without the necessity for such mediators. They utilise a coating

of electrically conducting organic salts, such as N-methylphenazinium cation (NMP+)

with tetracyanoquinodimethane radical anion. Many flavo-enzymes are strongly

adsorbed by such organic conductors due to the formation of salt links, utilising the

alternate positive and negative charges, within their hydrophobic environment. Such

enzyme electrodes can be prepared by simply dipping the electrode into a solution of

the enzyme and they may remain stable for several months. These electrodes can also

be used for reactions involving NAD(P)+-dependent dehydrogenases as they also

allow the electrochemical oxidation of the reduced forms of these coenzymes.The

reduction in oxidation potential, found when mediators are used, greatly reduces the

problem of interference by extraneous material.

Figure- (a) Ferrocene (5-bis-cyclopentadienyl iron), the parent compound of a

number of mediators. (b) TMP+, the cationic part of conducting organic crystals. (c)

TCNQ.-, the anionic part of conducting organic crystals.

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(d) Piezoelectric biosensor-

The piezoelectric effect in various crystalline substances is a useful property that

leads to the detection of analytes.

Principle-

Piezo-electric crystals (e.g. quartz) vibrate under the influence of an electric field.

The frequency of this oscillation (f) depends on their thickness and cut, each crystal

having a characteristic resonant frequency. This resonant frequency changes as

molecules adsorb or desorb from the surface of the crystal, obeying the relationships

Where, df is the change in resonant frequency (Hz), dm is the change in mass of

adsorbed material (g), K is a constant for the particular crystal dependent on such

factors as its density and cut, and A is the adsorbing surface area (cm2).

For any piezo-electric crystal, the change in frequency is proportional to the mass of

absorbed material, up to about a 2% change. This frequency change is easily detected

by relatively unsophisticated electronic circuits. A simple use of such a transducer is

a formaldehyde biosensor, utilising a formaldehyde dehydrogenase coating

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immobilised to a quartz crystal and sensitive to gaseous formaldehyde. They are

inexpensive, small and robust, and capable of giving a rapid response.

The piezoelectric crystal detector can be a very powerful analytical tool because of

the relationship shown for the change in frequency to the analyte concentration with

high sensitivity. Conversely, the above explanation shows that the crystal detector

indiscriminately changes frequency due to the deposition of mass of any material on

its surface. Thus, it is the task of the researcher to choose a coating that will undergo

a highly selective chemical or physical binding with the substance to be detected.

Only then can a highly selective sensor be constructed that will be sensitive to the

subject to be detected.

Disadvantage-

The major drawback of these devices is the interference from atmospheric humidity

and the difficulty in using them for the determination of material in solution.

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(e) Optical biosensor-

Optical biosensors measure both catalytic and affinity reactions. They measure a

change in fluorescence or in absorbance caused by the products generated by

catalytic reactions. Alternately, they measure the changes induced in the intrinsic

optical properties of the biosensor surface due to loading on it of dielectric molecules

like protein. A most promising biosensor involving luminescence uses firefly enzyme

luciferase for detection of bacteria in food or clinical samples. The bacteria are

specifically lysed to release ATP, which is used by luciferase in the presence of

oxygen to produce light which is measured by the biosensor.

There are two main areas of development in optical biosensors. These involve

determining changes in light absorption between the reactants and products of a

reaction, or measuring the light output by a luminescent process. The former usually

involve the widely established, if rather low technology, use of colorimetric test

strips.These are disposable single-use cellulose pads impregnated with enzyme and

reagents. The most common use of this technology is for whole-blood monitoring in

diabetes control. In this case, the strips include glucose oxidase, horseradish

peroxidase and a chromogen. The hydrogen peroxide, produced by the aerobic

oxidation of glucose, oxidizing the weakly coloured chromogen to a highly coloured

dye.

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Peroxidase

Chromogen (2H) + H2O2 dye + 2H2O

The evaluation of the dyed strips is best achieved by the use of portable reflectance

meters, although direct visual comparison with a coloured chart is often used.A most

promising biosensor involving luminescence uses firefly luciferase (Photinus-

luciferin 4-monooxygenase (ATP-hydrolysing), to detect the presence of bacteria in

food or clinical samples. Bacteria are specifically lysed and the ATP released

(roughly proportional to the number of bacteria present) reacted with D-luciferin and

oxygen in a reaction which produces yellow light in high quantum yield.

Luciferase

ATP + D-luciferin + O2 oxyluciferin + AMP +

pyrophosphate + CO2 + light (562 nm)

The light produced may be detected photometrically by use of high-voltage, and

expensive, photomultiplier tubes or low-voltage cheap photodiode systems. The

sensitivity of the photomultiplier-containing systems is < 104 cells ml-1, < 10-12 M

ATP than the simpler photon detectors which use photodiodes. Firefly luciferase is a

very expensive enzyme, only obtainable from the tails of wild fireflies. Use of

immobilised luciferase greatly reduces the cost of these analyses.

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(e) Immunochemical biosensors-

Biosensors may be used in conjunction with enzyme linked immunosorbent assays

(ELISA). Recently, ELISA techniques have been combined with biosensors, to formimmunosensors, in order to increase their range, speed and sensitivity. In the

immunosensor the biosensor merely replaces the traditional colorimetric detection

system. More advanced immunosensors are being developed which rely on the direct

detection of antigen bound to the antibody-coated surface of the biosensor.

It is not possible to produced a batch of antibody (called a monoclonal antibody)

which reacts specifically to one individual antigen. If the substance to the measured is

itself antigenic, then a specific antibody against it can be produced and can be

incorporated into the biosensor system. The biosensor can in this way be rendered

highly specific in its action.

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Figure - Principles of immunosensors. (a) (i) A tube is coated with (immobilized)

antigen. An excess of specific antibody-enzyme conjugate is placed in the tube and

allowed to bind. (a) (ii) After a suitable period any unbound material is washed off.

(a) (iii) The analyte antigen solution is passed into the tube, binding and releasing

some of the antibody-enzyme conjugate dependent upon the antigen's concentration.

The amount of antibody-enzyme conjugate released is determined by the response

from the biosensor. (b) (i) A transducer is coated with (immobilized) antibody,

specific for the antigen of interest. The transducer is immersed in a solution

containing a mixture of a known amount of antigen-enzyme conjugate plus unknown

concentration of sample antigen. (b) (ii) After a suitable period the antigen and

antigen-enzyme conjugate will be distributed between the bound and free states

dependent upon their relative concentrations. (b) (iii) Unbound material is washed

off and discarded. The amount of antigen-enzyme conjugate bound is determined

directly from the transduced signal.

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Immunochemical biosensor use immunological specificity with spectrophotometric

detection. Two main procedures can be used, the sandwich method and the

competitive method. In the first method, antibody (which reacts specifically with thesubstance to be measured, the analyte) is immobilized at the surface of a microplate

incubated with the analyte. After rinsing, a solution containing the antibody linked to

an enzyme is put in the microplate to read with the immobilized antibody analyte

complex from the first step.

The spectrophotometric detection involves measuring a coloured product of the

enzymatic reaction which reflects the number of analyte molecules and of the antigen

coupled to the enzyme when added to the immobilized antibody. After rinsing, the

enzymatic reaction is used to measure the number of antibodies which did not have

the analyte.

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(5.) APPLICATIONS:-

Biosensors are involved in many modern day to day activities i.e. employed in

domestic, industrial and research areas. Some of the most significant applications are

mentioned below.

(1.) Blood glucose monitoring-

Highly used in test of diabetes, a disease caused due to increased glucose content in

blood. A person is diagnosed diabetic if when his/her fasting blood glucose is greater

than or equal to 140 mg/dL (which under normal conditions is 115 mg/dL) and the

peak response to an oral glucose tolerance test would not exceed 200 mg/dL, falling

below 140 mg/dL 2 hours later. The diabetic will have a peak response exceeding 200

mg/dL, and his/her will remain above this level after two hours.

It is now possible for diabetics to determine their blood glucose at home. Usually this

is done four times daily, before each meal and before bedtime. A drop of blood is

obtained by pricking a finger. This sample is then placed on a reagent strip, which is

then analysed by an instrument using reflectance photometry. This was the earlier

method used. Nowadays, pen like biosensors are used that give results within few

minutes. The detailed mechanism has already been explained in second generation

biosensors.

(2.) Detection of pesticides and river water contamination-

Piezoelectric biosensors have been described for the detection of pesticides such as

the herbicide atrazine and the insecticide parathion. For instance, Guilbault et al.

have developed a direct detection device usingprotein A to orientate the antibodies

on the crystal adequately.Using this system, they achieved the detection of atrazine.

Based on catalytic antibodies this sensor combines the benefits of both

immunosensors and catalytic sensors. The antibody is immobilized on a pH electrodeand allows the detection ofphenyl acetate.

Optical biosensors are also helpful for environmental monitoring is based on surface

plasmon resonance (SPR) devices. An SPR immunosensor is a classical SPR device

modified with an immobilized antibody layer. When the antigen binds to the

immobilized antibody, the SPR device detects minute changes in the refractive index

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as a shift in the angle of total absorption of light incident on a metal layer carrying the

antibodies. Hence river water contamination can be analysed by biosensors.

(3.) Remote sensing of air borne bacteria and toxins-

Although there is no method present for complete detection of all air borne bacteria,

but when fiber-optic biosensor was integrated with an automated fluidics unit, a

cyclone-type air sampler, a radio transceiver, and batteries on a small radio-controlled

airplane, it was found to be able to collect aerosolized bacteria in flight, identify

them, and transmit the data back to the ground operator. Hence more biosensors

could be developed using this principle. Its main application lies in biowarfare.

Biosensor used for detection of toxins employs an immobilized luminescent Vibrio

fisherie bacterium to detect airborne contaminants. The presence of toxic chemicals

will lead to a detectable decrease in the intensity of light produced by the bacteria.

Important design factors are the appropriate cell growth media, environmental

toxicity, and oxygen and cell concentrations. The luminescent bacteria are

immobilized on polyvinyl alcohol (PVA) gels and placed inside a specially

constructed, miniature flow cell which houses a transducer, power source, and

transmitter to convert the light signal information into radio frequencies that are

picked up by a receiver at a remote location. These are a few examples of biosensor

used.

(4.) Detection of pathogens-

There are at present many methods to detect the presence of pathogens in food, and

other places but their detection with biosensor is most accurate and quick. Some

complex strains of viruses and bacteria require a few days to be detected. For

example -For the detection of pathogens such as Franscisela tularensis, and Yersinia

pestis (the bacterium that causes plague) we use a CANARY (cellular analysis and

notification of antigens risks and yields) biosensor.

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(5.) Test for presence of microbes in food-

A new biosensor made from mouse white blood cells has provided a quick and easy

test for microbes and toxins in food. The sensor can return results in just a few hours,

and it can be easily scaled to test up to 96 samples at one time . Because the sensor

uses mammalian cells it only returns a positive result if the bacteria or toxins are

active, and not if they have been denatured, meaning that unlike otherbiosensors it

only signals when the pathogens pose a real threat. The sensor consists of multi-well

plates, each containing mouse lymphocytes suspended in collagen gel. Each well can

test one sample, and there are typically 96 wells in a plate, so the technology is easily

scaled to test many samples at one time.

The sensor works by detecting when a toxin or bacteria has broken the cell wall of

the lymphocytes. This release an enzyme - alkaline phosphates - that can be marked

with another chemical to produce a yellow product, which can then be detected using

a spectrometer. The higher the quantity of the toxin or bacteria, the greater the

number of lymphocytes killed in this way, and the more intense the yellow colour in

the well. The spectrometer can detect the exact intensity of the colour of the well, and

through careful calibration it can estimate the quantity of the pathogen in the sample,

which can then be used to estimate the extent of the risk.

So far the sensor has detected small quantities of Bacillus species and Listeria

monocytogenes - a potent killer. In addition to its speed and high sensitivity to low

concentrations of toxins (with results comparable to PCR and antibody based

methods), the technique's key advantage is its reliance on the death of mammalian

cells, so it is very selective in signaling the presence of active, but not passive, toxins.

(6.) To determine level of toxicity before & after bioremediation-

Bioremediation can be defined as any process that uses microorganisms, fungi, green

plants or theirenzymes to return the natural environment altered by contaminants to

its original condition. Bioremediation may be employed to attack specific soil

contaminants, such as degradation of chlorinated hydrocarbons by bacteria). . The

process of bioremediation can be monitored indirectly by measuring the Oxidation

Reduction Potentialorredox in soil and groundwater, together withpH, temperature,

oxygen content, electron acceptor/donor concentrations, and concentration of

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breakdown products (e.g. carbon dioxide). For this purpose modern day biosensors

especially potentiometric and amperometric biosensors are widely used.

(7.) To study antigen antibody interaction-

For this technique, one of the interacting partners is immobilized on a sensor

chip(immunosensors) and the binding of the other is followed by the increase in

refractive index caused by the mass of bound species(optical biosensors). These

biosensors could be used for :-

(a) Functional mapping of epitopes and pratopes of mutagenesis.

(b) Analysis of the thermodynamic parameter of the interaction.

(c) Measurement of the concentration of biologically active molecules.

(d) Selection of diagnostic probes.

For instance an optical sensor system was developed, which allowed the

determination of pregnancy hormone chorionic gonadotropin (hCG), in human serum

with a detection limit of 1 mg/ml.

(8.) Biosensors and DNA analysis-

DNA can be used to identify organisms ranging from humans to bacteria and viruses.

The identification consists of reading the sequence of the DNA letters (A, G, C, and

T) that compose the alphabet used to describe the bases attached to the deoxyribose

phosphate polymer that forms the backbone of the DNA helix. Using methods to

form short sequences from the DNA of interest, DNA fragments are produced that

have one of the letters at their end and that differ according to their sizes. As a result,

DNAs containing 400 to 600 letters can be sequenced accurately. However, many

hours are required to prepare the fragments and separate them by size (using gel

electrophoresis). Using this method, the sequences of millions of DNA letters have

been determined, enabling the identification of the site of a genetic mutation that

causes such diseases as sickle cell anemia, Huntington's disease, fragile X syndrome

(a serious type of mental retardation), and several hundred other inherited diseases or

traits.

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Other Applications-

(1.) Detection and determining of organophosphate.

(2.) Routine analytical measurement of folic acid, biotin, vitamin B12 and

pantothenic acid as an alternative to microbiological assay.

(3.) Determination of drug residues in food, such as antibiotics and growth promoters,

particularly meat and honey.

(4.) Drug discovery and evaluation of biological activity of new compounds.

(5.) Detection of toxic metabolites such as mycotoxins.

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(6.) Conclusion-

Years from now, a typical doctor visit might not include instruments,instead, a chip

implanted in the body will function as a constant on-board doctor, detecting diseases

early and delivering drugs straight into the bloodstream. Biosensors could make this

scenario a reality before our toddler goes to college.Biosensors are already thriving in

the medical field. External biosensors are used in emergency rooms as point-of-care

diagnostic unitssuch as i-Stat's "lab on a chip," which can reveal almost

immediately whether a patient is in cardiac arrest by testing blood chemistry.

Other companies are developing implantable biosensors that track blood glucose

levels and deliver insulin. MicroChips is testing a chip implant that offers long-term,

time-controlled drug delivery. Digital Angel has discussed merging its external

biosensors with the VeriChip, an implantable microprocessor.

Despite the public's anticipation that biosensors with real-time detection will be able

to monitor biological and chemical weapons, the technology hasn't caught up with

expectations. Presently, biosensors in environmental monitoring stations nationwide

can detect compounds like anthraxbut detection can take 12 to 24 hours. The best

ones on the market take 20 minutes.

A type of biosensor could be incorporated into military uniforms and eventually into

houses as the biowarfare equivalent of a smoke detector. At the current rate of

technological progress, this real-time application could be ready within five years,

though the social issues involved could lengthen the process.

Experts disagree on how the focus on terrorism will affect biosensor development.

there's a concern that nonbiowarfare applications could get lost in the shuffle. One of

the most important applications is in industry, where biosensors monitor air quality

and emissions at chemical refineries and quality control at food-processing plants.

Currently, testers take random samples off the food line and use biosensors to detect

E. coli and salmonella.

If funding isn't diverted to military applications, within five to ten years biosensors

could be used in food lines to test every product.Biosensors and biosensor-related

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techniques that show potential for environmental applications must overcome a

number of obstacles to become commercially viable in the highly competitive area of

field analytical methods. Some of the obstacles common to all field analytical

methods include: the diversity of compounds and the complexity of matrices in

environmental samples, the variability in data quality requirements among

environmental programs, and the broad range of possible environmental monitoring

applications. More specific to biosensor technology, these hurdles include: relatively

high development costs for single analyte systems, limited shelf and operational

lifetimes for pre-manufactured biorecognition components and relative assay format

complexity for many potentially portable (but currently laboratory-based) biosensor

systems.

Advances in areas such as toxicity-, bioavailability-, and multi-pollutant-screening,

could widen the potential market and allow these techniques to be more competitive.

Miniaturization, reversibility and continuous operation may allow biosensor

techniques to be incorporated as detectors in chromatographic systems.

Because of the wide variability in environmental matrices, greater versatility in the

area of sample interface would be of considerable value. For example, classical

laboratory-based techniques typically employ extensive extraction and cleanup

protocols.

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(7.) Summary-

Technically, a biosensor is a probe that integrates a biological component, such as a

whole bacterium or a biological product (e.g., an enzyme or antibody) with an

electronic component to yield a measurable signal. One type of biosensor has only

five components: a biological sensing element, a transducer, a signal conditioner, a

data processor, and a signal generator. Biosensors can be classified according to their

transducers- calorimetric (heat measuring), potentiometric (potential measuring),

amperometric (measuring movement of electrons), optical (measuring light

characteristics), piezoelectric (detecting reactants and products) and immunochemical

(antigen antibody complex).

A successful biosensor must possess at least some of the following beneficial

features:

1. The biocatalyst must be highly specific for the purpose of the analysis, be stable

under normal storage conditions and, show good stability over a large number of

assays (i.e. much greater than 100).

2. The reaction should be independent of physical parameters such as stirring, pH andtemperature. This would allow the analysis of samples with minimal pre-treatment. If

the reaction involves cofactors or coenzymes these should, also be co-immobilised

with the enzyme.

3. The response should be accurate, precise, reproducible and linear over the useful

analytical range, without dilution or concentration. It should also be free from

electrical noise.

4. If the biosensor is to be used for invasive monitoring in clinical situations, the

probe must be tiny and biocompatible, having no toxic or antigenic effects.

If it is to be used in fermenters it should be sterilisable. This is performed by

autoclaving but no biosensor enzymes can presently withstand such drastic wet-heat

treatment. In either case, the biosensor should not be prone to fouling or proteolysis.

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5. The complete biosensor should be cheap, small, portable and capable of being used

by semi-skilled operators.

6. There should be a market for the biosensor. There is clearly little purpose

developing a biosensor if other factors (e.g. government subsidies, the continued

employment of skilled analysts, or poor customer perception) encourage the use of

traditional methods and discourage the decentralisation of laboratory testing.

The potential applications are:

1. Glucose monitoring in diabetes patients

2. Environmental applications e.g. the detection of pesticides and river water

contaminants

3. Remote sensing of airborne bacteria e.g. in counter-bioterrorist activities

4. Detection of pathogens.

5. Determining levels of toxic substances before and after bioremediation

6. Detection and determining of organophosphate

7. Routine analytical measurement of folic acid, biotin etc.

8. Determination of drug residues in food, such as antibiotics and growth promoters,

particularly meat and honey.

9. Drug discovery and evaluation of biological activity of new compounds.

10. Detection of toxic methabolites such as mycotoxins .

The relatively low cost of biosensors compared to classical methods such as

spectrophotometers etc. suggest that the use of biosensors seems promising since they

are also fast and portable analytical methods. Biosensors will undoubtedly play an

important role in future environmental monitoring practices. Nevertheless, some

critical parameters such as stability, accuracy and reliability still have to be improved

in order to transfer biosensor technology to industrial and domestic applications.

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(8.) References-

1. Li Q, Yuan J;Development of the Portable Blood Glucose Meter for Self-

monitoring of Blood Glucose; Conf Proc IEEE Eng Med Biol Soc. 2005;

7:6735-8.

2. Rodriguez-Mozaz S, de Alda MJ, Barcel D; Fast and simultaneous

monitoring of organic pollutants in a drinking water treatment plant by a

multi-analyte biosensor followed by LC-MS validation; Talanta. 2006 Apr

15;69(2):377-84.

3. Liu X, Sun Y, Song D, Zhang Q, Tian Y, Zhang H; Enhanced optical

immuosensor based on surface plasmon resonance for determination of

transferring; Talanta.2006 Jan 15;68(3):1026-31.

4. Skottrup P, Nicolaisen M, Justesen AF; Rapid determination of Phytophthorainfestans sporangia using a surface plasmon resonance immunosensor; J

Microbiol Methods. 2007 Mar;68(3):507-15.

5. Skottrup PD, Nicolaisen M, Justesen AF; Towards on-site pathogen detection

using antibody-based sensors; Biosens Bioelectron.2008 Nov 15;24(3):339-

48.

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6. Miyashita M, Ito N, Ikeda S, Murayama T, Oguma K, Kimura J;

Development of urine glucose meter based on micro-planer amperometric

biosensor and its clinical application for self-monitoring of urine glucose;

Biosens Bioelectron. 2008 Aug 13.

7. Ly SY,Cho NS; Diagnosis of human hepatitis B virus in non-treated blood

by the bovine IgG DNA-linked carbon nanotube biosensor; J Clin Virol. 2008

Oct 31.

8. Liang R, Jiang J, Qiu J ; An amperometric glucose biosensor based on

titania sol-gel/Prussian Blue composite film; Anal Sci. 2008;24(11):1425-30.

9. Galbn J, Sanz V, Mateos E,Sanz-Vicente I, Delgado-Camn A,de Marcos

S; Reagentless optical biosensors for organic compounds based on auto-

indicating proteins; Protein Pept Lett. 2008;15(8):772-8.

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