Electrochemical biosensor for rapid and sensitive detection of magnetically extracted bacterial pathogens

Bioreceptor modified electrochemical biosensors for the detection of life threating pathogenic bacteria: a review

The lack of reliable and efficient techniques for early monitoring to stop long-term effects on human health is an increasing problem as the pathogenesis effect of infectious bacteria is growing continuously. Therefore, developing an effective early detection technique coupled with efficient and continuous monitoring of pathogenic bacteria is increasingly becoming a global public health prime target. Electrochemical biosensors are among the strategies that can be utilized for accomplishing that goal with promising potential. In recent years, identifying target biological analytes by interacting with bioreceptors modified electrodes is among the most commonly used detection techniques in electrochemical biosensing strategies. The commonly employed bioreceptors are nucleic acid molecules (DNA or RNA), proteins, antibodies, enzymes, organisms, tissues, and biomimetic components such as molecularly imprinted polymers. Despite the advancement in electrochemical biosensing, developing a reliable and effective biosensor for detecting pathogenic bacteria is still in the infancy stage with so much room for growth. A major milestone in addressing some of the issues and improving the detection pathway is the investigation of specific bacterial detection techniques. The present study covers the fundamental concepts of electrochemical biosensors, human PB illnesses, and the latest electrochemical biosensors based on bioreceptor elements that are designed to detect specific pathogenic bacteria. This study aims to assist researchers with the most up-to-date research work in the field of bio-electrochemical pathogenic bacteria detection and monitoring.

Disposable electrochemical biosensors for the detection of bacteria in the light of antimicrobial resistance

Persistent and inappropriate use of antibiotics is causing rife antimicrobial resistance (AMR) worldwide. Common bacterial infections are thus becoming increasingly difficult to treat without the use of last resort antibiotics. This has necessitated a situation where it is imperative to confirm the infection to be bacterial, before treating it with antimicrobial speculatively. Conventional methods of bacteria detection are either culture based which take anywhere between 24 and 96 hor require sophisticated molecular analysis equipment with libraries and trained operators. These are difficult propositions for resource limited community healthcare setups of developing or less developed countries. Customized, inexpensive, point-of-care (PoC) biosensors are thus being researched and developed for rapid detection of bacterial pathogens. The development and optimization of disposable sensor substrates is the first and crucial step in development of such PoC systems. The substrates should facilitate easy charge transfer, a high surface to volume ratio, be tailorable by the various bio-conjugation chemistries, preserve the integrity of the biorecognition element, yet be inexpensive. Such sensor substrates thus need to be thoroughly investigated. Further, if such systems were made disposable, they would attain immunity to biofouling. This article discusses a few potential disposable electrochemical sensor substrates deployed for detection of bacteria for environmental and healthcare applications. The technologies have significant potential in helping reduce bacterial infections and checking AMR. This could help save lives of people succumbing to bacterial infections, as well as improve the overall quality of lives of people in low- and middle-income countries.

The effect of magnetic bead size on the isolation efficiency of lung cancer cells in a serpentine microchannel with added cavities

An investigation was conducted to examine the effect of magnetic bead (MB) size on the effectiveness of isolating lung cancer cells using the immunomagnetic separation (IMS) method in a serpentine microchannel with added cavities (SMAC) structure. Carboxylated magnetic beads were specifically conjugated to target cells through a modification procedure using aptamer materials. Cells immobilized with different sizes (in micrometers) of MBs were captured and isolated in the proposed device for comparison and analysis. The study yields significance regarding the clarification of device working principles by using a computational model. Furthermore, an accurate evaluation of the MB size impact on capture efficiency was achieved, including the issue of MB-cell accumulation at the inlet-channel interface, despite it being overlooked in many previous studies. As a result, our findings demonstrated an increasing trend in binding efficiency as the MB size decreased, evidenced by coverages of 50.5%, 60.1%, and 73.4% for sizes of 1.36 μm, 3.00 μm, and 4.50 μm, respectively. Additionally, the overall capture efficiency (without considering the inlet accumulation) was also higher for smaller MBs. However, when accounting for the actual number of cells entering the channel (i.e., the effective capture), larger MBs showed higher capture efficiency. The highest effective capture achieved was 88.4% for the size of 4.50 μm. This research provides an extensive insight into the impact of MB size on the performance of IMS-based devices and holds promise for the efficient separation of circulating cancer cells (CTCs) in practical applications.

Advancing biological investigations using portable sensors for detection of sensitive samples

Portable biosensors are emerged as powerful diagnostic tools for analyzing intricately complex biological samples. These biosensors offer sensitive detection capabilities by utilizing biomolecules such as proteins, nucleic acids, microbes or microbial products, antibodies, and enzymes. Their speed, accuracy, stability, specificity, and low cost make them indispensable in forensic investigations and criminal cases. Notably, portable biosensors have been developed to rapidly detect toxins, poisons, body fluids, and explosives; they have proven invaluable in forensic examinations of suspected samples, generating efficient results that enable effective and fair trials. One of the key advantages of portable biosensors is their ability to provide sensitive and non-destructive detection of forensic samples without requiring extensive sample preparation, thereby reducing the possibility of false results. This comprehensive review provides an overview of the current advancements in portable biosensors for the detection of sensitive materials, highlighting their significance in advancing investigations and enhancing sensitive sample detection capabilities.

Iron/iron oxide-based magneto-electrochemical sensors/biosensors for ensuring food safety: recent progress and challenges in environmental protection

Foodborne diseases have arisen due to the globalization of industry and the increase in urban population, which has led to increased demand for food and has ultimately endangered the quality of food. Foodborne diseases have caused some of the most common public health problems and led to significant social and economic issues worldwide. Food quality and safety are affected by microbial contaminants, growth-promoting feed additives (β-agonists and antibiotics), food allergens, and toxins in different stages from harvesting to storage and marketing of products. Electrochemical biosensors, due to their reduced size and portability, low cost, and low consumption of reagents and samples, can quickly provide valuable quantitative and qualitative information about food contamination. In this regard, using nanomaterials can increase the sensitivity of the assessment. Magnetic nanoparticle (MNP)-based biosensors, especially, are receiving significant attention due to their low-cost production, physicochemical stability, biocompatibility, and eco-friendly catalytic characteristics, along with magnetic, biological, chemical and electronic sensing features. Here, we provide a review on the application of iron-based magnetic nanoparticles in the electrochemical sensing of food contamination. The types of nanomaterials used in order to improve the methods and increase the sensitivity of the methods have been discussed. Then, we stated the advantages and limitations of each method and tried to state the research gaps for each platform/method. Finally, the role of microfluidic and smartphone-based methods in the rapid detection of food contamination is stated. Then, various techniques like label-free and labelled regimes for the sensitive monitoring of food contamination were surveyed. Next, the critical role of antibody, aptamer, peptide, enzyme, DNA, cells and so on for the construction of specific bioreceptors for individual and simultaneous recognition by electrochemical methods for food contamination were discussed. Finally, integration of novel technologies such as microfluidic and smartphones for the identification of food contaminations were investigated. It is important to point out that, in the last part of each sub-section, attained results of different reports for each strategy were compared and advantages/limitations were mentioned.

Portable dual-aptamer microfluidic chip biosensor for Bacillus cereus based on aptamer tailoring and dumbbell-shaped probes

As food-borne pathogens, Bacillus cereus not only produce toxins that contaminate food and threaten human health, but also rely on spores to resist extreme environments. At present, the detection of B. cereus is still at the genome level and it is not easily distinguished from other Bacilli of the same group. Herein, we obtained the aptamers of B. cereus in different phases through Cell-SELEX technology. Then, through step-by-step tailoring and molecular docking, the two best performing aptamers were ascertained and the interaction revealed between the repeated G bases in the aptamer and the polar amino acids in the α-helix of the epiprotein. Based on these aptamers, a multifunctional dumbbell-shaped probe and an ultrasensitive microfluidic chip biosensor were designed. Tests showed that the novel sensor is able to complete detection within 1 h with a limit of detection (LOD) of 9.27 CFU/mL. Moreover, the sensor can be used in complex food environments, such as milk and rice, is able to detect both vegetative cells and spores, and it can also distinguish B. thuringiensis from the same flora. This study can provide a reference for the future development of food-borne pathogenic bacteria aptamer selecting, target interaction analysis, detection methods and equipment.

Advances, applications, and limitations of portable and rapid detection technologies for routinely encountered foodborne pathogens

Traditional foodborne pathogen detection methods are highly dependent on pre-treatment of samples and selective microbiological plating to reliably screen target microorganisms. Inherent limitations of conventional methods include longer turnaround time and high costs, use of bulky equipment, and the need for trained staff in centralized laboratory settings. Researchers have developed stable, reliable, sensitive, and selective, rapid foodborne pathogens detection assays to work around these limitations. Recent advances in rapid diagnostic technologies have shifted to on-site testing, which offers flexibility and ease-of-use, a significant improvement from traditional methods' rigid and cumbersome steps. This comprehensive review aims to thoroughly discuss the recent advances, applications, and limitations of portable and rapid biosensors for routinely encountered foodborne pathogens. It discusses the major differences between biosensing systems based on the molecular interactions of target analytes and biorecognition agents. Though detection limits and costs still need further improvement, reviewed technologies have high potential to assist the food industry in the on-site detection of biological hazards such as foodborne pathogens and toxins to maintain safe and healthy foods. Finally, this review offers targeted recommendations for future development and commercialization of diagnostic technologies specifically for emerging and re-emerging foodborne pathogens.

Silver Halide-Based Nanomaterials in Biomedical Applications and Biosensing Diagnostics

In recent years, silver halide (AgX, X = Cl, Br, I)-based photocatalytic materials have received increasing research attention owing to their excellent visible-light-driven photocatalytic performance for applications in organic pollutant degradation, HER, OER, and biomedical engineering. Ag as a noble metal has a surface plasma effect and can form Schottky junctions with AgX, which significantly promotes electron transport and increases photocatalytic efficiency. Therefore, Ag/AgX can reduce the recombination rate of electrons and holes more than pure AgX, leading to using AgX as a photocatalytic material in biomedical applications. The use of AgX-based materials in photocatalytic fields can be classified into three categories: AgX (Ag/AgX), AgX composites, and supported AgX materials. In this review, we introduce recent developments made in biomedical applications and biosensing diagnostics of AgX (Ag/AgX) photocatalytic materials. In addition, this review also discusses the photocatalytic mechanism and applications of AgX (Ag/AgX) and supported AgX materials.

Overview on the Design of Magnetically Assisted Electrochemical Biosensors

Electrochemical biosensors generally require the immobilization of recognition elements or capture probes on the electrode surface. This may limit their practical applications due to the complex operation procedure and low repeatability and stability. Magnetically assisted biosensors show remarkable advantages in separation and pre-concentration of targets from complex biological samples. More importantly, magnetically assisted sensing systems show high throughput since the magnetic materials can be produced and preserved on a large scale. In this work, we summarized the design of electrochemical biosensors involving magnetic materials as the platforms for recognition reaction and target conversion. The recognition reactions usually include antigen-antibody, DNA hybridization, and aptamer-target interactions. By conjugating an electroactive probe to biomolecules attached to magnetic materials, the complexes can be accumulated near to an electrode surface with the aid of external magnet field, producing an easily measurable redox current. The redox current can be further enhanced by enzymes, nanomaterials, DNA assemblies, and thermal-cycle or isothermal amplification. In magnetically assisted assays, the magnetic substrates are removed by a magnet after the target conversion, and the signal can be monitored through stimuli-response release of signal reporters, enzymatic production of electroactive species, or target-induced generation of messenger DNA.

Electrochemical Detection of Waterborne Bacteria Using Bi-Functional Magnetic Nanoparticle Conjugates

Detection of microbial contamination in water is imperative to ensure water quality. We have developed an electrochemical method for the detection of E. coli using bi-functional magnetic nanoparticle (MNP) conjugates. The bi-functional MNP conjugates were prepared by terminal-specific conjugation of anti-E. coli IgG antibody and the electroactive marker ferrocene. The bi-functional MNP conjugate possesses both E. coli-specific binding and electroactive properties, which were studied in detail. The conjugation efficiency of ferrocene and IgG antibodies with amine-functionalized MNPs was investigated. Square-wave voltammetry enabled the detection of E. coli concentrations ranging from 10¹-10⁷ cells/mL in a dose-dependent manner, as ferrocene-specific current signals were inversely dependent on E. coli concentrations, completely suppressed at concentrations higher than 10⁷ cells/mL. The developed electrochemical method is highly sensitive (10 cells/mL) and, coupled to magnetic separation, provides specific signals within 1h. Overall, the bi-functional conjugates serve as ideal candidates for electrochemical detection of waterborne bacteria. This approach can be applied for the detection of other bacteria and viruses.

Electrochemical immunosensor based on mussel inspired coating for simultaneous detection and elimination of Staphylococcus aureus in drinks

Staphylococcus aureus (S. aureus) is one of the most commonly isolated foodborne pathogens, and is considered as a major cause of foodborne illnesses worldwide. However, the development of smart and accurate analytical methods for the simultaneous detection and elimination of S. aureus in matrices of food or drinks remains challenging. In the present work, a mussel-inspired material, ε-poly-l-lysine-3,4-dihydroxy benzaldehyde (EPD), was designed and fabricated based on its Schiff base structure. Owing to the robust ability of the material to adhere onto wet electrode surfaces and the pH-responsive properties of EPD, the prepared immunosensor exhibited an excellent detection limit and linear range with on-demand antibacterial activity. In real milk samples, the average values obtained from the immunosensor were approximate to the standard results obtained from the plate count method, and the relative standard deviation was 3.16–6.54%, suggesting the good accuracy of the developed method. Moreover, it exhibited good selectivity, reproducibility, and stability, thus demonstrating the potential significant applications of the electrochemical immunosensor in drinks safety monitoring.

A smart electrochemical immunosensor for the detection and elimination of Staphylococcus aureus in food with on-demand antibacterial activity.

Development of magnetosomes-based biosensor for the detection of Listeria monocytogenes from food sample

Listeriosis through contaminated food is one of the leading causes of premature deaths in pregnant women and new born babies. Here, the authors have developed a magnetosomes-based biosensor for the rapid, sensitive, specific and cost-effective detection of Listeria monocytogenes from food sample. Magnetosomes were extracted from Magnetospirillum sp. RJS1 and then directly bound to anti-Listeriolysin antibody (0.25-1 µg/ml), confirmed in spectroscopy. Listeriolysin (LLO) protein (0.01-7 µg/ml) was optimised in enzyme-linked immunosorbent assay. Magnetosomes was conjugated with LLO antibody (0.25 µg/ml) in optimum concentration to detect LLO protein (0.01 µg/ml). Magnetosomes-LLO antibody complex was 25% cost effective. The magnetosomes-LLO antibody complex was directly stabilised on screen printed electrode using external magnet. The significant increase in resistance (R_CT value) on the electrode surface with increase in concentration of LLO protein was confirmed in impedance spectroscopy. The L. monocytogenes contaminated milk and water sample were processed and extracted LLO protein was detected in the biosensor. The specificity of the biosensor was confirmed in cross-reactivity assay with other food pathogens. The detection limit of 10¹ Cfu/ml in both water and milk sample manifests the sensitive nature of the biosensor. The capture efficiency and field emission scanning electron microscopy confirmed positive interaction of Listeria cells with magnetosomes-antibody complex.

Comparative Study of Electrochemical Biosensors Based on Highly Efficient Mesoporous ZrO2-Ag-G-SiO2 and In2O3-G-SiO2 for Rapid Recognition of E. coli O157:H7

Here, we reported an innovative and electrochemical biosensor for the rapid detection of Escherichia coli O157:H7. We fabricated the mesoporous ZrO2-Ag-G-SiO2 (ZAGS) and In2O3-G-SiO2 (IGS) sensors, and cyclic voltammetry (CV) was employed to detect the bacteria. The development of these portable sensors addresses the challenges of conventional time-consuming and more expensive laboratory-based analyses. Hence, the biosensors were highly selective to detect E. coli. The sensor could recognize an individual E. coli cell in 1 μL of sample volume within 30 s. E. coli live cells tied down on sample nanoparticles worked toward the definite acquirement of E. coli. The high thickness of negative charge on the surface of E. coli cells effectively regulated the concentration of dominant part charge carriers in the mesoporous channel, allowing a continuous check of E. coli concentration in a known sample. The signal current decreased linearly, while the E. coli concentration increased from 1.0 × 101 to 1.0 × 1010 CFU/mL. ZAGS and IGS biosensors could detect E. coli in the range from 101 to 1010 CFU/mL. ZAGS and IGS biosensors in this investigation showed great specificity, reproducibility, stability, and selectivity and are expected to have a great impact on applications in the detection of foodborne pathogens.

Flexible nanopillar-based immunoelectrochemical biosensor for noninvasive detection of Amyloid beta

The noninvasive early detection of biomarkers for Alzheimer's disease (AD) is essential for the development of specific treatment strategies. This paper proposes an advanced method for fabricating highly ordered and flexible nanopillar-based electrochemical biosensors by the combination of soft/photolithography and metal evaporation. The nanopillar array (NPA) exhibits high surface area containing 1500 nm height and 500 nm diameter with 3:1 ratio. In regard with physical properties of polyurethane (PU) substrate, the developed NPA is sustainable and durable to external pressure such as bending and twisting. To manipulate the NPA surface to biocompatible, the gold was uniformly deposited on the PU substrate. The thiol chemistry which is stably modified on the gold surface as a form of self-assembled monolayer was employed for fabricating the NPA as a biocompatible chip by covalently immobilize the antibodies. The proposed nanopillar-based immunoelectrochemical biosensor exhibited good and stable electrochemical performance in β-amyloid (Aβ) detection. Moreover, we successfully confirmed the performance of the as-developed sensor using the artificial injection of Aβ in human tear, with sensitivity of 0.14 ng/mL and high reproducibility (as a standard deviation below 10%). Our findings show that the developed nanopillar-based sensor exhibits reliable electrochemical characteristics and prove its potential for application as a biosensor platform for testing at the point of care.

Development of an Electrochemical Immunosensor for Specific Detection of Visceral Leishmaniasis Using Gold-Modified Screen-Printed Carbon Electrodes

Visceral leishmaniasis is a reemerging neglected tropical disease with limitations for its diagnosis, including low concentration of antibodies in the serum of asymptomatic patients and cross-reactions. In this context, this work proposes an electrochemical immunosensor for the diagnosis of visceral leishmaniasis in a more sensitive way that is capable of avoiding cross-reaction with Chagas disease (CD). Crude Leishmania infantum antigens tested in the enzyme-linked immunosorbent assay (ELISA) were methodologically standardized to best engage to the sensor. The antibodies anti-Trypanosoma cruzi and anti-Leishmania sp. Present in serum from patients with diverse types of CD or leishmaniasis were chosen. A screen-printed carbon electrode modified with gold nanoparticles was the best platform to guarantee effective adsorption of all antigens so that the epitope of specific recognition for leishmaniasis occurred efficiently and without cross-reaction with the evaluated CD. The current peaks reduced linearly after the recognition, and still were able to notice the discrimination between different kinds of diseases (digestive, cardiac, undetermined Chagas/acute and visceral chronic leishmaniasis). Comparative analyses with ELISA were performed with the same groups, and a low specificity (44%) was verified due to cross-reactions (high number of false positives) on ELISA tests, while the proposed immunosensor presented high selectivity and specificity (100%) without any false positives or false negatives for the serum samples from isolated patients with different types of CD and visceral leishmaniasis. Furthermore, the biosensor was stable for 5 days and presented a detection limit of 200 ng mL⁻¹.

Magnetosome-anti-Salmonella antibody complex based biosensor for the detection of Salmonella typhimurium

Epidemic Salmonellosis contracted through the consumption of contaminated food substances is a global concern. Thus, simple and effective diagnostic methods are needed. Magnetosome-based biosensors are gaining attention because of their promising features. Here, we developed a biosensor employing a magnetosome-anti-Salmonella antibody complex to detect lipopolysaccharide (somatic "O" antigen) and Salmonella typhimurium in real samples. Magnetosome was extracted from Magnetospirillum sp. RJS1 and characterized by microscopy. The magnetosome samples (1 and 2 mg/mL) were directly conjugated to anti-Salmonella antibody (0.8-200 μg/mL) and confirmed by spectroscopy and zeta potential. The concentrations of magnetosome, antibody and lipopolysaccharide were optimized by ELISA. The 2 mg/mL-0.8 μg/mL magnetosome-antibody complex was optimal for detecting lipopolysaccharide (0.001 μg/mL). Our assay is a cost-effective (60%) and sensitive (50%) method in detection of lipopolysaccharide. The optimized magnetosome-antibody complex was applied to an electrode surface and stabilized using an external magnetic field. Increased resistance confirmed the detection of lipopolysaccharide (at 0.001-0.1 μg/mL) using impedance spectroscopy. Significantly, the R² value was 0.960. Then, the developed prototype biosensor was applied to food and water samples. ELISA confirmed the presence of lipopolysaccharide in homogenized infected samples and cross reactivity assays confirmed the specificity of the biosensor. Further, the biosensor showed low detection limit (10¹ CFU/mL) in water and milk sample demonstrating its sensitivity. Regression coefficient of 0.974 in water and 0.982 in milk was obtained. The magnetosome-antibody complex captured 90% of the S. typhimurium in real samples which was also confirmed in FE-SEM. Thus, the developed biosensor is selective, specific, rapid and sensitive for detection of S. typhimurium.

Advanced Methods for Detection of Bacillus cereus and Its Pathogenic Factors

Bacillus cereus is an opportunistic foodborne pathogen causing food intoxication and infectious diseases. Different toxins and pathogenic factors are responsible for diarrheal syndrome, like nonhemolytic enterotoxin Nhe, hemolytic enterotoxin Hbl, enterotoxin FM and cytotoxin K, while emetic syndrome is caused by the depsipeptide cereulide toxin. The traditional method of B. cereus detection is based on the bacterial culturing onto selective agars and cells enumeration. In addition, molecular and chemical methods are proposed for toxin gene profiling, toxin quantification and strain screening for defined virulence factors. Finally, some advanced biosensors such as phage-based, cell-based, immunosensors and DNA biosensors have been elaborated to enable affordable, sensitive, user-friendly and rapid detection of specific B. cereus strains. This review intends to both illustrate the state of the B. cereus diagnostic field and to highlight additional research that is still at the development level.

Non-lytic M13 phage-based highly sensitive impedimetric cytosensor for detection of coliforms

A highly sensitive and selective non-lytic M13 phage-based electrochemical impedance spectroscopy (EIS) cytosensor for early detection of coliforms is introduced for the first time. Gold nanoparticles were electrochemically deposited on the surface of glassy carbon electrode, and the M13 phage particles were immobilized on them using 3-mercaptopropionic acid linker and zero-length crosslinking chemistry (EDC/NHS). Next, the sensor surface was blocked to avoid non-specific binding. The M13-EIS cytosensor was tested for detection of F⁺ pili Escherichia coli species, using XL1-Blue and K12 strains, as examples of coliforms. The selectivity against non-host strains was demonstrated using Pseudomonas Chlororaphis. The binding of E. coli to the M13 phage on the cytosensor surface increased the charge transfer resistance, enabling detection of coliforms. The biosensor achieved a limit of detection (LOD) of 14 CFU/mL, the lowest reported to-date using EIS-phage sensors, and exhibited a high selectivity towards the tested coliforms. The SEM micrographs confirmed the successful capturing of E. coli on the M13-based EIS cytosensor. Moreover, the sensor showed almost the same sensitivity in the simulated river water samples as in phosphate buffer, reflecting its applicability to real samples. On the other hand, this sensor system exhibited high stability under harsh environmental conditions of pH (3.0-10.0) and temperature as high as 45 °C for up to two weeks. Overall, this sensor system has excellent potential for real field detection of fecal coliforms.

Microfluidic-Based Approaches for Foodborne Pathogen Detection

Food safety is of obvious importance, but there are frequent problems caused by foodborne pathogens that threaten the safety and health of human beings worldwide. Although the most classic method for detecting bacteria is the plate counting method, it takes almost three to seven days to get the bacterial results for the detection. Additionally, there are many existing technologies for accurate determination of pathogens, such as polymerase chain reaction (PCR), enzyme linked immunosorbent assay (ELISA), or loop-mediated isothermal amplification (LAMP), but they are not suitable for timely and rapid on-site detection due to time-consuming pretreatment, complex operations and false positive results. Therefore, an urgent goal remains to determine how to quickly and effectively prevent and control the occurrence of foodborne diseases that are harmful to humans. As an alternative, microfluidic devices with miniaturization, portability and low cost have been introduced for pathogen detection. In particular, the use of microfluidic technologies is a promising direction of research for this purpose. Herein, this article systematically reviews the use of microfluidic technology for the rapid and sensitive detection of foodborne pathogens. First, microfluidic technology is introduced, including the basic concepts, background, and the pros and cons of different starting materials for specific applications. Next, the applications and problems of microfluidics for the detection of pathogens are discussed. The current status and different applications of microfluidic-based technologies to distinguish and identify foodborne pathogens are described in detail. Finally, future trends of microfluidics in food safety are discussed to provide the necessary foundation for future research efforts.

Detection of Salmonella in Food Matrices, from Conventional Methods to Recent Aptamer-Sensing Technologies

Rapid detection of the foodborne pathogen Salmonella in food processing is of crucial importance to prevent food outbreaks and to ensure consumer safety. Detection and quantification of Salmonella species in food samples is routinely performed using conventional culture-based techniques, which are labor intensive, involve well-trained personnel, and are unsuitable for on-site and high-throughput analysis. To overcome these drawbacks, many research teams have developed alternative methods like biosensors, and more particularly aptasensors, were a nucleic acid is used as biorecognition element. The increasing interest in these devices is related to their high specificity, convenience, and relative rapid response. This review aims to present the advances made in these last years in the development of biosensors for the detection and the quantification of Salmonella, highlighting applications on meat from the chicken food chain.

Current Trends in the Biosensors for Biological Warfare Agents Assay

Biosensors are analytical devices combining a physical sensor with a part of biological origin providing sensitivity and selectivity toward analyte. Biological warfare agents are infectious microorganisms or toxins with the capability to harm or kill humans. They can be produced and spread by a military or misused by a terrorist group. For example, Bacillus anthracis, Francisella tularensis, Brucella sp., Yersinia pestis, staphylococcal enterotoxin B, botulinum toxin and orthopoxviruses are typical biological warfare agents. Biosensors for biological warfare agents serve as simple but reliable analytical tools for the both field and laboratory assay. There are examples of commercially available biosensors, but research and development of new types continue and their application in praxis can be expected in the future. This review summarizes the facts and role of biosensors in the biological warfare agents' assay, and shows current commercially available devices and trends in research of the news. Survey of actual literature is provided.

Emerging nano-biosensing with suspended MNP microbial extraction and EANP labeling

Emerging nano-biosensing with suspended MNP microbial extraction and EANP labeling may ensure a secure microbe-free food supply, as rapid response detection of microbial contamination is of utmost importance. Many biosensor designs have been proposed over the past two decades, covering a broad range of binding ligands, signal amplification, and detection mechanisms. These designs may consist of self-contained test strips developed from the base up with complicated nanoparticle chemistry and intricate ligand immobilization. Other methods use multiple step-wise additions, many based upon ELISA 96-well plate technology with fluorescent detection. In addition, many biosensors use expensive antibody receptors or DNA ligands. But many of these proposed designs are impracticable for most applications or users, since they don't FIRST address the broad goals of any biosensor: Field operability, Inexpensive, with Real-time detection that is both Sensitive and Specific to target, while being as Trouble-free as possible. Described in this review are applications that utilize versatile magnetic nanoparticles (MNP) extraction, electrically active nanoparticles (EANP) labeling, and carbohydrate-based ligand chemistry. MNP provide rapid pathogen extraction from liquid samples. EANP labeling improves signal amplification and expands signaling options to include optical and electrical detection. Carbohydrate ligands are inexpensive, robust structures that are increasingly synthesized for higher selectivity. Used in conjunction with optical or electrical detection of gold nanoparticles (AuNP), carbohydrate-functionalized MNP-cell-AuNP nano-biosensing advances the goal of being the FIRST biosensor of choice in detecting microbial pathogens throughout our food supply chain.

Nanomaterials: Electrochemical Properties and Application in Sensors

The unique properties of nanoparticles make them an extremely valuable modifying material, being used in electrochemical sensors. The features of nanoparticles affect the kinetics and thermodynamics of electrode processes of both nanoparticles and redox reactions occurring on their surface. The paper describes theoretical background and experimental studies of these processes. During the transition from macro- to micro- and nanostructures, the analytical characteristics of sensors modify. These features of metal nanoparticles are related to their size and energy effects, which affects the analytical characteristics of developed sensors. Modification of the macroelectrode with nanoparticles and other nanomaterials reduces the detection limit and improves the degree of sensitivity and selectivity of measurements. The use of nanoparticles as transducers, catalytic constituents, parts of electrochemical sensors for antioxidant detection, adsorbents, analyte transporters, and labels in electrochemical immunosensors and signal-generating elements is described.

Development of MoSe₂ Nano-Urchins as a Sensing Platform for a Selective Bio-Capturing of Escherichia. coli Shiga Toxin DNA

The present study was aimed to develop "fluorine doped" tin oxide glass electrode with a MoSe2 nano-urchin based electrochemical biosensor for detection of Escherichia. coli Shiga toxin DNA. The study comprises two conductive electrodes, and the working electrodes were drop deposited using MoSe2 nano-urchin, and DNA sequences specific to Shiga toxin Escherichia. coli. Morphological characterizations were performed using Fourier transforms infrared spectrophotometer; X-ray diffraction technique and scanning electron microscopy. All measurements were done using methylene blue as an electrochemical indicator. The proposed electrochemical geno-sensor showed good linear detection range of 1 fM⁻100 μM with a low detection limit of 1 fM where the current response increased linearly with Escherichia. coli Shiga toxin dsDNA concentration with R2 = 0.99. Additionally, the real sample was spiked with the dsDNA that shows insignificant interference. The results revealed that the developed sensing platform significantly improved the sensitivity and can provide a promising platform for effective detection of biomolecules using minute samples due to its stability and sensitivity.

Application of Aptamer-Based Biosensor for Rapid Detection of Pathogenic Escherichia coli

Pathogenic Escherichia coli (E. coli) widely exist in Nature and have always been a serious threat to the human health. Conventional colony forming units counting-based methods are quite time consuming and not fit for rapid detection for E. coli. Therefore, novel strategies for improving detection efficiency and sensitivity are in great demand. Aptamers have been widely used in various sensors due to their extremely high affinity and specificity. Successful applications of aptamers have been found in the rapid detection of pathogenic E. coli. Herein, we present the latest advances in screening of aptamers for E. coli, and review the preparation and application of aptamer-based biosensors in rapid detection of E. coli. Furthermore, the problems and new trends in these aptamer-based biosensors for rapid detection of pathogenic microorganism are also discussed.

Electrochemical Methodologies for the Detection of Pathogens

Bacterial infections remain one of the principal causes of morbidity and mortality worldwide. The number of deaths due to infections is declining every year by only 1% with a forecast of 13 million deaths in 2050. Among the 1400 recognized human pathogens, the majority of infectious diseases is caused by just a few, about 20 pathogens only. While the development of vaccinations and novel antibacterial drugs and treatments are at the forefront of research, and strongly financially supported by policy makers, another manner to limit and control infectious outbreaks is targeting the development and implementation of early warning systems, which indicate qualitatively and quantitatively the presence of a pathogen. As toxin contaminated food and drink are a potential threat to human health and consequently have a significant socioeconomic impact worldwide, the detection of pathogenic bacteria remains not only a big scientific challenge but also a practical problem of enormous significance. Numerous analytical methods, including conventional culturing and staining techniques as well as molecular methods based on polymerase chain reaction amplification and immunological assays, have emerged over the years and are used to identify and quantify pathogenic agents. While being highly sensitive in most cases, these approaches are highly time, labor, and cost consuming, requiring trained personnel to perform the frequently complex assays. A great challenge in this field is therefore to develop rapid, sensitive, specific, and if possible miniaturized devices to validate the presence of pathogens in cost and time efficient manners. Electrochemical sensors are well accepted powerful tools for the detection of disease-related biomarkers and environmental and organic hazards. They have also found widespread interest in the last years for the detection of waterborne and foodborne pathogens due to their label free character and high sensitivity. This Review is focused on the current electrochemical-based microorganism recognition approaches and putting them into context of other sensing devices for pathogens such as culturing the microorganism on agar plates and the polymer chain reaction (PCR) method, able to identify the DNA of the microorganism. Recent breakthroughs will be highlighted, including the utilization of microfluidic devices and immunomagnetic separation for multiple pathogen analysis in a single device. We will conclude with some perspectives and outlooks to better understand shortcomings. Indeed, there is currently no adequate solution that allows the selective and sensitive binding to a specific microorganism, that is fast in detection and screening, cheap to implement, and able to be conceptualized for a wide range of biologically relevant targets.

Detection of Antibiotics and Evaluation of Antibacterial Activity with Screen-Printed Electrodes

This review provides a brief overview of the fabrication and properties of screen-printed electrodes and details the different opportunities to apply them for the detection of antibiotics, detection of bacteria and antibiotic susceptibility. Among the alternative approaches to costly chromatographic or ELISA methods for antibiotics detection and to lengthy culture methods for bacteria detection, electrochemical biosensors based on screen-printed electrodes present some distinctive advantages. Chemical and (bio)sensors for the detection of antibiotics and assays coupling detection with screen-printed electrodes with immunomagnetic separation are described. With regards to detection of bacteria, the emphasis is placed on applications targeting viable bacterial cells. While the electrochemical sensors and biosensors face many challenges before replacing standard analysis methods, the potential of screen-printed electrodes is increasingly exploited and more applications are anticipated to advance towards commercial analytical tools.

Voltammetric determination of the Escherichia coli DNA using a screen-printed carbon electrode modified with polyaniline and gold nanoparticles

The authors describe an electrochemical assay for fast detection of Escherichia coli (E. coli). It is based on a dual signal amplification strategy and the use of a screen-printed carbon electrode (SPCE) whose surface was modified with a polyaniline (PANI) film and gold nanoparticles (AuNPs) via cyclic voltammetry (CV). In the next step, avidin was covalently immobilized on the PANI/AuNP composite on the SPCE surface. Subsequently, the biotinylated DNA capture probe was immobilized onto the PANI/AuNP/avidin-modified SPCE by biotin-avidin interaction. Then, DNA of E.coli, digoxigenin-labeled DNA detector probe and anti-digoxigenin-labeled horseradish peroxidase (HRP) were placed on the electrode. 3,3',5,5'-Tetramethylbenzidine (TMB) and H₂O₂ solution were added and the CV electrochemical signal was generated at a potential of -0.1 V (vs. Ag/AgCl) and a scan rate 50 mV.s^-1. The assay can detect 4 × 10⁶ to 4 CFU of E. coli without DNA amplification. The biosensor is highly specific over other pathogens including Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis, Staphylococcus haemolyticus and Pseudomonas aeruginosa. It can be concluded that this genosensor has an excellent potential for rapid and accurate diagnosis of E.coli inflicted infections. Graphical Abstract Schematic of an electrochemical E. coli genosensor based on sandwich assay on a polyaniline/gold nanoparticle-modified screen printed carbon electrode (SPCE). The biosensor can detect 4 × 10⁶ to 4 CFU of E. coli without DNA amplification.

Biosensors for rapid and sensitive detection of Staphylococcus aureus in food

Foodborne illness outbreaks caused by the consumption of food contaminated with harmful bacteria has drastically increased in the past decades. Therefore, detection of harmful bacteria in the food has become an important factor for the recognition and prevention of problems associated with food safety and public health. Staphylococcus aureus is one of the most commonly isolated foodborne pathogen and it is considered as a major cause of foodborne illnesses worldwide. A number of different methods have been developed for the detection and identification of S. aureus in food samples. However, some of these methods are laborious and time-consuming and are not suitable for on-site applications. Therefore, it is highly important to develop rapid and more approachable detection methods. In the last decade, biosensors have gained popularity as an attractive alternative method and now considered as one of most rapid and on-site applicable methods. An overview of the biosensor based methods used for the detection of S. aureus is presented herein. This review focuses on the state-of-the-art biosensor methods towards the detection and quantification of S. aureus, and discusses the most commonly used biosensor methods based on the transducing mode, such as electrochemical, optical, and mass-based biosensors.

Graphene-based label-free electrochemical aptasensor for rapid and sensitive detection of foodborne pathogen

Reduced graphene oxide (rGO) has emerged as a promising nanomaterial for reliable detection of pathogenic bacteria due to its exceptional properties such as ultrahigh electron transfer ability, large surface to volume ratio, biocompatibility, and its unique interactions with DNA bases of the aptamer. In this study, rGO-azophloxine (AP) nanocomposite aptasensor was developed for a sensitive, rapid, and robust detection of foodborne pathogens. Besides providing an excellent conductive and soluble rGO nanocomposite, the AP dye also acts as an electroactive indicator for redox reactions. The interaction of the label-free single-stranded deoxyribonucleic acid (ssDNA) aptamer with the test organism, Salmonella enterica serovar Typhimurium (S. Typhimurium), was monitored by differential pulse voltammetry analysis, and this aptasensor showed high sensitivity and selectivity for whole-cell bacteria detection. Under optimum conditions, this aptasensor exhibited a linear range of detection from 10⁸ to 10¹ cfu mL^-1 with good linearity (R ² = 0.98) and a detection limit of 10¹ cfu mL^-1. Furthermore, the developed aptasensor was evaluated with non-Salmonella bacteria and artificially spiked chicken food sample with S. Typhimurium. The results demonstrated that the rGO-AP aptasensor possesses high potential to be adapted for the effective and rapid detection of a specific foodborne pathogen by an electrochemical approach. Graphical abstract Fabrication of graphene-based nanocomposite aptasensor for detection of foodborne pathogen.

Field-Effect Biosensors for On-Site Detection: Recent Advances and Promising Targets

There is an explosive interest in the immediate and cost-effective analysis of field-collected biological samples, as many advanced biodetection tools are highly sensitive, yet immobile. On-site biosensors are portable and convenient sensors that provide detection results at the point of care. They are designed to secure precision in highly ionic and heterogeneous solutions with minimal hardware. Among various methods that are capable of such analysis, field-effect biosensors are promising candidates due to their unique sensitivity, manufacturing scalability, and integrability with computational circuitry. Recent developments in nanotechnological surface modification show promising results in sensing from blood, serum, and urine. This report gives a particular emphasis on the on-site efficacy of recently published field-effect biosensors, specifically, detection limits in physiological solutions, response times, and scalability. The survey of the properties and existing detection methods of four promising biotargets, exosomes, bacteria, viruses, and metabolites, aims at providing a roadmap for future field-effect and other on-site biosensors.

Current Technical Approaches for the Early Detection of Foodborne Pathogens: Challenges and Opportunities

The development of novel and high-tech solutions for rapid, accurate, and non-laborious microbial detection methods is imperative to improve the global food supply. Such solutions have begun to address the need for microbial detection that is faster and more sensitive than existing methodologies (e.g., classic culture enrichment methods). Multiple reviews report the technical functions and structures of conventional microbial detection tools. These tools, used to detect pathogens in food and food homogenates, were designed via qualitative analysis methods. The inherent disadvantage of these analytical methods is the necessity for specimen preparation, which is a time-consuming process. While some literature describes the challenges and opportunities to overcome the technical issues related to food industry legal guidelines, there is a lack of reviews of the current trials to overcome technological limitations related to sample preparation and microbial detection via nano and micro technologies. In this review, we primarily explore current analytical technologies, including metallic and magnetic nanomaterials, optics, electrochemistry, and spectroscopy. These techniques rely on the early detection of pathogens via enhanced analytical sensitivity and specificity. In order to introduce the potential combination and comparative analysis of various advanced methods, we also reference a novel sample preparation protocol that uses microbial concentration and recovery technologies. This technology has the potential to expedite the pre-enrichment step that precedes the detection process.

Multifunctional Nanotechnology-Enabled Sensors for Rapid Capture and Detection of Pathogens

Nanomaterial-based sensing approaches that incorporate different types of nanoparticles (NPs) and nanostructures in conjunction with natural or synthetic receptors as molecular recognition elements provide opportunities for the design of sensitive and selective assays for rapid detection of contaminants. This review summarizes recent advancements over the past ten years in the development of nanotechnology-enabled sensors and systems for capture and detection of pathogens. The most common types of nanostructures and NPs, their modification with receptor molecules and integration to produce viable sensing systems with biorecognition, amplification and signal readout are discussed. Examples of all-in-one systems that combine multifunctional properties for capture, separation, inactivation and detection are also provided. Current trends in the development of low-cost instrumentation for rapid assessment of food contamination are discussed as well as challenges for practical implementation and directions for future research.

An integrated microfluidic PCR system with immunomagnetic nanoparticles for the detection of bacterial pathogens

There is growing interest in rapid microbial pre-concentration methods to lower the detection limit of bacterial pathogens of low abundance in samples. Here, we report an integrated microfluidic PCR system that enables bacterial cells of interest in samples to be concentrated prior to PCR. It consists of two major compartments: a preconcentration chamber for the immunomagnetic separation of bacterial cells, and a PCR chamber for the DNA amplification of the concentrated cells. We demonstrate the feasibility of the system for the detection of microbial pathogens by preconcentrating the human pathogen Escherichia coli O157:H7, and also amplifying its DNA. The detection limit of E. coli O157:H7 in the PCR system is 1 × 10³ CFU (colony forming unit)/mL. On-chip processing steps, including preconcentration and PCR steps, take less than two hours. Our system can serve as a rapid, specific, and quantitative platform for the detection of microbial pathogens in samples of large volume.

Charge-Directed Immobilization of Bacteriophage on Nanostructured Electrode for Whole-Cell Electrochemical Biosensors

A new type of carbon nanotube (CNT)-based impedimetric biosensing method has been developed for rapid and selective detection of live bacterial cells. A proof-of-concept study was conducted using T2 bacteriophage-based biosensors for electrochemical detection of Escherichia coli B. The T2 bacteriophage (virus) served as the biorecognition element, which was immobilized on polyethylenimine (PEI)-functionalized carbon nanotube transducer on glassy carbon electrode. Charge-directed, orientated immobilization of bacteriophage particles on carbon nanotubes was achieved through covalent linkage of phage capsid onto the carbon nanotubes. The presence of the immobilized phage on carbon nanotube-modified electrode was confirmed by fluorescence microscopy. Electrochemical impedance spectroscopy (EIS) was used to monitor the changes in the interfacial impedance due to the binding of E. coli B to T2 phage on the CNT-modified electrode. The detection was highly selective toward the B strain of E. coli as no signal was observed for the nonhost K strain of E. coli. The present achievable detection limit of the biosensor is 10³ CFU/mL.

Surface Imprints: Advantageous Application of Ready2use Materials for Bacterial Quartz-Crystal Microbalance Sensors

Four different materials (two ab initio synthesized polyurethanes; ready-to-use: Epon1002F and poly(vinyl alcohol)/N-methyl-4(4'-formylstyryl)pyridinium methosulfate acetal) for the generation of Escherichia coli surface imprints are compared in this work. The use of commercially available, ready-to-use materials instead of self-synthesized polymers represents an innovative and convenient way of molecular imprint fabrication. This was herein investigated for large, biological templates. Fully synthesized imprint materials (polyurethanes) were developed and optimized regarding their OH excess and the use of catalyst in the polymerization reaction. No to low OH excess (0-10%) and a noncatalyzed synthesis were determined to be superior for the imprinting of the Gram-negative bacteria. Imprints were characterized using atomic force microscopy, with Epon1002F yielding the most distinguished imprints, along with a smooth surface. The imprints were afterward tested as plastic antibody coatings in a mass-sensitive quartz-crystal microbalance measurement. Dilutions of E. coli suspensions, down to a limit of detection of 1.4 × 10⁷ CFU/mL, were successfully measured. Best results were obtained with Epon1002F and self-synthesized, stoichiometric polyurethane. Since ready-to-use Epon1002F was superior in terms of signal intensities and sensitivity, it can advantageously replace self-synthesized polymers for the generation of imprinted sensor surfaces. Easy day-to-day reproducibility and further shortening of imprint fabrication time are other advantages of employing the ready-to-use material instead of conventionally synthesized polymers.

An electrochemical biosensor for rapid detection of E. coli O157:H7 with highly efficient bi-functional glucose oxidase-polydopamine nanocomposites and Prussian blue modified screen-printed interdigitated electrodes

The presence of pathogenic bacteria in foods has always been a great threat to the wellbeing of people and the revenue of food manufacturers. Therefore, the demand for advanced detection methods that can sensitively and rapidly detect these pathogens has been of great importance. This study reports an electrochemical biosensor for rapid detection of E. coli O157:H7 with the integration of bifunctional glucose oxidase (GOx)-polydopamine (PDA) based polymeric nanocomposites (PMNCs) and Prussian blue (PB) modified screen-printed interdigitated microelectrodes (SP-IDMEs). The core-shell magnetic beads (MBs)-GOx@PDA PMNCs were first synthesized by the self-polymerization of dopamine (DA). Gold nanoparticles (AuNPs) were dispersed on the surface of PMNCs through biochemical synthesis to achieve further highly efficient adsorption of antibodies (ABs) and GOx. The final product ABs/GOxext/AuNPs/MBs-GOx@PDA PMNCs served as the carrier to separate target bacteria from food matrices as well as the amplifier for electrochemical measurement. The unbound PMNCs were separated by a filtration step and transferred into glucose solution to allow the enzymatic reaction to occur. The change of the current response was measured with an electrochemical detector using PB-modified SP-IDMEs. The constructed biosensor has been proven to be able to detect E. coli O157:H7 with the detection limit of 10(2) cfu ml(-1). The bifunctional PMNCs contain a high load of enzyme and can optimally utilize the binding sites on bacterial cells, which efficiently amplify the signals for measurement. The biosensor in this study exhibited good specificity, reproducibility, and stability and is expected to have a great impact on applications in the detection of foodborne pathogens.

Recent Advancements in Nanobioassays and Nanobiosensors for Foodborne Pathogenic Bacteria Detection

Bacterial pathogens are one of the leading causes of food safety incidents and product recalls worldwide. Timely detection and identification of microbial contamination in agricultural and food products is crucial for disease prevention and outbreak investigation. In efforts to improve and/or replace time-consuming and laborious "gold standards" for pathogen detection, numerous alternative rapid methods have been proposed in the past 15 years, with a trend toward incorporating nanotechnology and nanomaterials in food pathogen detection. This article is a review of the use of nanotechnology in various detection and sample preparation techniques and advancements in nanotechnology applications in food matrices. Some practical considerations in nanobioassay design are discussed, and the gaps between research status quo and market demands are identified.

Fundamentals, achievements and challenges in the electrochemical sensing of pathogens

Electrochemical sensors are powerful tools widely used in industrial, environmental and medical applications. The versatility of electrochemical methods allows for the investigation of chemical composition in real time and in situ. Electrochemical detection of specific biological molecules is a powerful means for detecting disease-related markers. In the last 10 years, highly-sensitive and specific methods have been developed to detect waterborne and foodborne pathogens. In this review, we classify the different electrochemical techniques used for the qualitative and quantitative detection of pathogens. The robustness of electrochemical methods allows for accurate detection even in heterogeneous and impure samples. We present a fundamental description of the three major electrochemical sensing methods used in the detection of pathogens and the advantages and disadvantages of each of these methods. In each section, we highlight recent breakthroughs, including the utilisation of microfluidics, immunomagnetic separation and multiplexing for the detection of multiple pathogens in a single device. We also include recent studies describing new strategies for the design of future immunosensing systems and protocols. The high sensitivity and selectivity, together with the portability and the cost-effectiveness of the instrumentation, enhances the demand for further development in the electrochemical detection of microbes.

Highly sensitive bacteria quantification using immunomagnetic separation and electrochemical detection of guanine-labeled secondary beads

In this paper, we report the ultra-sensitive indirect electrochemical detection of E. coli O157:H7 using antibody functionalized primary (magnetic) beads for capture and polyguanine (polyG) oligonucleotide functionalized secondary (polystyrene) beads as an electrochemical tag. Vacuum filtration in combination with E. coli O157:H7 specific antibody modified magnetic beads were used for extraction of E. coli O157:H7 from 100 mL samples. The magnetic bead conjugated E. coli O157:H7 cells were then attached to polyG functionalized secondary beads to form a sandwich complex (magnetic bead/E. coli secondary bead). While the use of magnetic beads for immuno-based capture is well characterized, the use of oligonucleotide functionalized secondary beads helps combine amplification and potential multiplexing into the system. The antibody functionalized secondary beads can be easily modified with a different antibody to detect other pathogens from the same sample and enable potential multiplexing. The polyGs on the secondary beads enable signal amplification up to 10⁸ guanine tags per secondary bead (7.5 x 10⁶ biotin-FITC per secondary bead, 20 guanines per oligonucleotide) bound to the target (E. coli). A single-stranded DNA probe functionalized reduced graphene oxide modified glassy carbon electrode was used to bind the polyGs on the secondary beads. Fluorescent imaging was performed to confirm the hybridization of the complex to the electrode surface. Differential pulse voltammetry (DPV) was used to quantify the amount of polyG involved in the hybridization event with tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)3(2+)) as the mediator. The amount of polyG signal can be correlated to the amount of E. coli O157:H7 in the sample. The method was able to detect concentrations of E. coli O157:H7 down to 3 CFU/100 mL, which is 67 times lower than the most sensitive technique reported in literature. The signal to noise ratio for this work was 3. We also demonstrate the use of the protocol for detection of E. coli O157:H7 seeded in waste water effluent samples.