Biosensors : tool for food borne pathogen detection

A paramount and alluring sphere of research, now-a-days, is food analysis, because of the breakneck augmentation of food enterprise and highly hightened maneuverability of today's populations. The management of food quality is very indispensable both for consumer safeguard as well as the food corporations. The biosensors' application in the field of food analysis is quite propitious for the revealing of food borne pathogens. Biosensor, an analytical device, transforms a biological response into an electrical signal. Bioreceptors and transducers are the two main components of a biosensor. Bioreceptor or biorecognition element is the one which leads to the recognition of target analyte and a transducer, for the conversion of recognized event into a measurable electrical signal. The development of biosensors improved the sensitivity and selectivity of detection techniques for food borne pathogens and is rapid, reliable, effective and highly suitable when used in in situ analysis. Since the security in the food supply becomes crucial because of increased perception among consumers and vying nature of food industries, the necessity for expeditious, low volume and sensitive biosensor devices has productively increased. TM Nevertheless , till date, a very few biosensor systems are available commercially such as Biacore, Spreeta , Reichert SR 7000, Analyte 2000, RAPTOR etc. Since, there is ever growing concern regarding safe food and water supply, it is very obvious that the demand for rapid detecting biosensors will also be increasing at par.


Introduction
rapid and destructive changes, process control is chief point in a modern industrial environment.Hence, there Food products and their raw materials are composed is an expanding demand for analytical technology of complex compounds, therefore, to guarantee its appropriate for automatic quality control through the high-quality principles and security, the quality control process and at the end of the line so that the real-time is the foremost task allied with food industries [1].
state of the process can be restricted [5].In addition to Even if the food security has significantly enhanced , rapid results, on-line biosensor technology offers food advancement is uneven, furthermore microbial containdustry a choice of internal process control to fulfill mination, chemicals and toxins leading to food borne the interest of a high standard of quality control.outbreaks are widespread in several countries.It has Biosensor is an analytical device assimilating a been estimated that the food industry spends on an meticulous and essential amalgam of a specific average, 1.5%-2% of the value of its total sales on biological element (that constitute a perceptive action) quality control and appraisal [2].According to a new and a physical element (that transduces the perceptive market report of Strategic Consulting Inc. entitled action).For easy understanding, the term biosensor Food Micro 2005, the worldwide food microbiology signifies a fusion of biology and sensing, a sensor market in 2005 represented over 25 million $ tests with competent enough to recognize an analyte, a biological a market value in excess of 1.65 billion $ [3].Food sample, and transmit and interpret signal [6].The finest manufactured might be microbiologically contamiillustration of a biosensor in human body is the nose, nated at base level or at either stage while processing, competent of distinguishing odor molecules and packaging or distribution.Biosensors have elevated transmitting a signal to the brain.It comprises of two potential for automation and permit the construction of chief components: a bioreceptor or biorecognition simple and portable equipment for fast analysis [4].For element, which perceives the desired analyte and a the reason that most food is extremely sensitive to transducer, for translating the predicted event into a critical process parameters and can effortlessly undergo quantifiable electrical signal [7].The fundamental characteristics of a biosensor [8] comprise linearity (linearity of the sensor should be high for the detection of high substrate concentration), sensitivity (Value of the electrode response per substrate concentration), Enzyme bioreceptor: Enzyme as bioreceptors offer selectivity (chemicals interference must be minimized numerous advantages over fluorescently labeled and for obtaining the correct result) and response time radio labeled substances and enzyme immunoassay (time necessary for having 95% of the response).
reagents are highly stable, sensitive and there are no The first biosensor was characterized by Clark health hazards.Enzyme immobilization emerges as a and Lyons in 1962.A Clark oxygen electrode was fundamental aspect to evolve competent biosensors combined with the enzyme glucose oxidase to monitor with relevant properties such as good operational and glucose levels.The co-reactant oxygen could be storage stability, immense sensitivity, high selectivity, monitored amperometrically which was produced short response time and large reproducibility [13].The while glucose underwent enzymatic oxidation [9].On most frequently used enzyme is Horseradish Peroxidase the other hand, the production of hydrogen peroxide (HRP) and beta-galactoxidase.The detection of pathoduring the enzyme reaction could be measured.Since genic bacteria such as Listeria monocytogenes, Escherichia then, much work was published on enzyme electrodes.
coli and Campylobacter jejuni can be done by labeling Enzymes were immobilized with diverse procedures the antibody with these enzymes.and reaction substrates or products were revealed by Bacteriophage bioreceptors: Bacteriophages (phages) distinct methods.In 1969, Guilbault and Montalvo are viruses of 20-200 nm in size [14] that unite to reported the first enzyme biosensor based on definite receptors on the bacterial surface in order to potentiometry.Rchenitz charcterized a selective NH 3 infuse their genetic material inside the bacteria.Phages gas sensing electrode for arginine in 1977 and used the identify the bacterial receptors via its tail spike proteins.term 'bioselective sensor' and this term was at a later They have noticeable edge over other biorecognition date abbreviated to "biosensor" [10].
receptors.Amid these, advantages are the specificity of

Classification of biosensors
the synergy of this sort of virus with its target host cell, its skill to lyse and kill its host, plus its ability to Conventionally biosensors may be classified reproduce throughout the infection process [15].In (Table -1) according to the mechanism of biological addition, they are omnipresent, innocuous to humans, selectivity (bioreceptor) otherwise, on the mode of economically and conveniently produced, have a physiochemical signal transduction (transducers).
distant longer shelf life as they endure harsh environ-Bioreceptors: A bioreceptor is a molecular species that ments, diminishing the environmental limitations and exploits a biochemical mechanism for recognition.
enabling regeneration of the biosensor surface.They are accountable for binding the concerned analyte Researchers have proclaimed the function of phage as a to the sensor for measurement [7].Bioreceptors can biorecognition component for the exposure of various broadly be classified into five distinct classes.These pathogens such as E. coli [14], Staphylococcus aureus classes comprise antibody-antigen bioreceptor, enzymatic [16] and Bacillus anthracis spores [17,18] by adopting bioreceptor, nucleic acids (DNA) bioreceptor, cellular diverse sensing platforms.structures or cellular bioreceptor, biomimetic bioreceptor Nucleic acid bioreceptors: The precise biorecognition and bacteriophage bioreceptor.
in DNA biosensors depends on the complementarity of Antibody bioreceptor: Antibodies are universal bioadenine: thymine (A:T) and cytosine:guanosine (C:G) receptors used in biosensors.The antibodies may be pairing in DNA which is known to form the foundation polyclonal, monoclonal or recombinant based on their for, generally referred to as genosensors.Nucleic acid selective properties and synthesis.Nonetheless, they based biosensors have been proclaimed by several are usually immobilized on a substrate, which can be researchers for the detection of food pathogen like E. the detector surface, its vicinity, or a carrier [11].An coli O157:H7 [19], Salmonella spp.
[20], C. jejuni [21] antigen-specific antibody fits its exclusive antigen in etc.An additional type of biosensor employs a peptide extremely specific way alike to a lock and key [12], so nucleic acid as the biorecognition element [22].The that the three-dimensional structures of antigen and peptide nucleic acid (PNA) is a synthetic oligo amide antibody molecules are corresponding.This inimitable that is competent of binding incredibly firmly to property of antibodies is the key that makes the complimentary oligonucleotide sequences.Although immunosensors influential analytical tool and their the major drawback of PNA is that their synthesis is skill to distinguish molecular structures allows one to very costly.But the key disadvantage is that Purinedevelop antibodies that bind exclusively to any of the rich PNA oligomers tend to cumulate and are weakly chemicals or biomolecules or microorganisms etc.
soluble in aqueous media [23].Cell based biosensor: Cellular structures and cells the most precise of the optical techniques [29].These have been operated in the evolution of biosensors and sensitive biosensors can also be used in order to biochips [24].Isolation of cell organelles can be done identify various food borne pathogens viz., E. coli O157:H7 [16], Salmonella [30], L. monocytogenes for utilizing them as bioreceptors.Cell organelles are [31] and C. jejuni [32].The scope of electrochemical necessarily exclusive system which recognizes it to be biosensor has developed expeditiously in eventual few exploited for long course of time.Mammalian tissue years.There has been immense breakthrough in the slices or in vitro cultured mammalian cells can be well advancement of electrochemical sensors for detecting employed as biosensing elements in bioreceptors [25].
virus infection and bacterial contamination [7].The reason for suitability of living cells as recognition Reymond et al. [33] devised an amperometric detection element are [7] :a) they provide sensitivity to biochemethod for the determination of the presence, the mical stimuli, secondly, b) they present functional amount, and the concentration of an analyte in a micro analysis for biochemical agents and lastly, c) their fluidic sensor.There have also been disclosures related detection can be very low due to signal amplification.
to the evolution of a biosensor for the estimation of The elementary illustration of a cell-based sensing protein and amino acid [34].Electrochemical biosensors system using collagen-encapsulated mammalian cells developed on the basis of amperometric detection were for rapid detection of pathogenic bacteria or toxin was found linked with other biosensing techniques.For presented by Banerjee et al. [26].Advancement of an example, a bienzyme electrochemical biosensor was artificial cell-based biosensor, which exploits liposomefound helpful in the detection of pathogens like E. coli doped silica nano-composite, has been noted by Zhao O157:H7 [35], Salmonella Typhimurium [36].et al. [27].It mimics existing whole-cell assays for Listeriolysin O (LLO) which is a pore-forming hemolysin Potentiometric biosensors: Potentiometric biosensors secreted by pathogen L. monocytogenes.
involve the utilization of ion-selective electrodes in order to transduce the biological reaction into an Transducers: The transducer plays a crucial part in the electrical signal.Thus, it is simply comprised of an detection and identification process of a biosensor.
immobilised enzyme membrane which surrounds the Biosensors can also be designated on the basis of the probe from a pH-meter and the hydrogen ions are transduction systems they engage.The transduction generated or absorbed here via catalyzed reaction.The methods such as optical, electrochemical and mass reaction happening adjunct to the thin sensing glass based are the most favored and universal methods.
membrane directs the change in pH which can be read Mass sensitive biosensors: Assessment of minute directly from the pH-meter's display.Light-addressable transformation in mass is a distinct configuration of potentiometric sensor (LAPS) for the detection of transduction that has been exploited for biosensors.
pathogens has been reported [37].Gehring et al. [38] The fundamental mode of mass analysis relies on the developed an immune-ligand assay (ILA) in conjunction account of piezoelectric crystals [28].This results in with a light-addressable potentiometric sensor (LAPS) the vibration of crystals at a distinct frequency with the for the rapid detection of E. coli O157:H7 cells in operation of an electrical signal of explicit frequency.buffered saline.Zhang et al.
[39] has developed a Therefore, the frequency of oscillation depends on the potentiometric flow biosensor based on ammoniaelectrical frequency which is applied to the crystal and oxidizing bacteria for the detection of toxicity in water.its mass [7].Thus, in simple words, binding of Impedimetric detection: The thought of electrical chemicals results in increase in mass which in turn impedance measurement of microbial growth was put changes the oscillation frequency of the crystal which forward by G.N.Stewart in 1899, however, the method can be measured electrically and utilized in the deterwas employed for the first time in 1970s for this mination of the additional crystal mass.The detection purpose.Impedance is defined as the apparent of L. monocytogenes has been conceivable with the resistance in an electric circuit to the flow of alternating development of a quartz crystal microbalance current, which corresponds to the actual electrical biosensor [16].
resistance to a direct current.Thus, its principle is Electrochemical biosensors: These are addendum of based on the changes in the conductance of the medium conventional antibody based enzyme immunoassays due to microbial metabolism of the inert substrates into (ELISA), which comprises the catalysis of substrates electrically charged ionic compounds and acidic-byby an enzyme conjugated to an antibody and the products (e.g.amino acids, lactic acid and acetic production of products which in turn can be detected in acid).This causes a change in electrical impedance and the pattern of pH change, ion or oxygen consumption conductance of the medium.Bacterial growth in a due to generation of electrical signals on a transducer [7].
medium which can be related to the function of time at a given temperature can be monitored by carefully Amperometric biosensors: Amperometric transducmonitoring and measuring electrical impedance and tion is universal electrochemical detection method conductance.which has been well exploited for pathogen detection.
At present, impedance instruments are able to This technique is very integral to optical detection 5 6 detect 10 -10 bacteria/ml.Some commercially available methods such as fluorescence, which is considered as systems such as the Bactometer (bioMerieux), Malthus The advantages affiliated with this are that it takes less TM time to detect binding events and since it is label-free, it AT analyzer (Malthus Instruments), BacTrac are used excludes additional reagents, assays and steps.There for pathogen monitoring and quality assurance have been many reports on SPR based biosensors by purposes.Yang et al. [40] used inter-digitated microvarious researchers for the identification of different electrodes as impedance sensors for rapid detection of food borne pathogens such as L. monocytogenes [46], viable salmonella.
Staphyloccocus [47], and E. coli O157:H7 [48,49].Optical biosensors: Optical biosensors are dynamic Commercially available SPR systems are also available TM substitute to accustomed scientific techniques which now which includes: BIACORE, Spreeta , SPR can be well related to their particularly high specifispectroscope, Optrel GbR, Reichert SR7000 and cation, sensitivity, small size, and relatively cost effec-IAsys.Among all these, the detection of E. coli tiveness [41].The research and high-tech development O157:H7 [50] and L. monocytogenes [51], Salmonella of optical biosensors have gained an exponential [52] can be done by Spreeta™ biosensor and growth during the last decade because of the linear, BIACORE 3000 respectively.real-time and label-free detection of many chemical

Commercially available biosensors
and biological substances by this technique [42].
Regardless of the enormous collection of publica-

Raman and Fourier Transformed Infra-red Spectroscopy
tions on biosensors implemented in food analysis, (FT-IR): Fourier transform spectroscopy is a computathere are very limited entities which are commercially tional technique which involves the collection of available [53].The utilization and commercialization spectra based on calculation and evaluation of the of biosensor technology has diminished far behind the coherence of a radiative source with the help of time output of research laboratories.There are many domain or space-domain measurements of the electrobiosensor-related patents filed each year, however very magnetic radiation or any other type of radiation.
few play a prominent role in food industry (Table -2).

Schmilovitch et al. [43] operated a dispersive system
There have been many apprehensions for the slow spectrophotometer, with a 785 nm diode laser for the technology transfer from the research laboratory to the detection of Gram-positive and Gram-negative bacteria.market place: limited lifetime of the biological Whereas, another application of this technique components, mass production, quality assurance and includes the detection and differentiation of live and instrumentation design and the most decisive one is the heated Salmonella enterica serovars inoculated onto lack of cogency, organized commercialization approaches.chicken breast by Davis et al. [44].FT-IR has also been exploited for the compliation or recognition of various Upcoming techniques, future developments food borne pathogens: Yersinia, Staphylococcus, Listeria, The most promising breakthroughs are to be Klebsiella, Enterobacter, Citrobacter, Salmonella.FTexpected in the area of biosensor technology (Table -3), IR spectrometry can be implemented to detect E. coli that will allow the creation of on-line or on-site, O157: H7 from ground beef [45].
sensitive, low-cost devices for routine use [53].Biosensors have high potential for automation and allow the Surface plasmon resonance (SPR): SPR is a robust construction of simple and portable equipment for fast tool that can measure the binding kinetics of two molecules without the help of any fluorescent tag.
analysis.Biosensor advancement, in the commercial Thus, this technique can be said as a peculiarity that world could be accelerated by the use of intelligent appears during optical illumination of a metal surface instrumentation, electronics, and multi-variate signaland can be adopted for biomolecular interaction analysis.processing methods.

Table - 2
. Commercially available biosensors (The names of commercial products/companies used in this study are for information purpose only.Authors or institute of authors do not recommend the use of these products)

Table - 3
. Upcoming biosensors in near future (The names of commercial products/companies used in this study are for information purpose only.Authors or institute of authors do not recommend the use of these products)