Enzyme-linked immuno-strip biosensor to detect Escherichia coli O157:H7

Rapid-format recombinant antibody-based methods for the diagnosis of Clostridioides difficile infection: Recent advances and perspectives

Clostridioides difficile, the most common cause of nosocomial diarrhea, has been continuously reported as a worldwide problem in healthcare settings. Additionally, the emergence of hypervirulent strains of C. difficile has always been a critical concern and led to continuous efforts to develop more accurate diagnostic methods for detection of this recalcitrant pathogen. Currently, the diagnosis of C. difficile infection (CDI) is based on clinical manifestations and laboratory tests for detecting the bacterium and/or its toxins, which exhibit varied sensitivity and specificity. In this regard, development of rapid diagnostic techniques based on antibodies has demonstrated promising results in both research and clinical environments. Recently, application of recombinant antibody (rAb) technologies like phage display has provided a faster and more cost-effective approach for antibody production. The application of rAbs for developing ultrasensitive diagnostic tools ranging from immunoassays to immunosensors, has allowed the researchers to introduce new platforms with high sensitivity and specificity. Additionally, DNA encoding antibodies are directly accessible in these approaches, which enables the application of antibody engineering to increase their sensitivity and specificity. Here, we review the latest studies about the antibody-based ultrasensitive diagnostic platforms for detection of C. difficile bacteria, with an emphasis on rAb technologies.

Advanced trap lateral flow immunoassay sensor for the detection of cortisol in human bodily fluids

Paper-based biosensors based on lateral flow immunoassay (LFI) are promising candidates for POC diagnosis because of their ease of use and rapid target detection. However, the low sensitivity of LFI limits its application, and signal amplification has been used in numerous studies to increase its sensitivity. We developed an advanced trap LFI (α-trapLFI), a simple-to-use sensor, with an additional step for signal amplification. Here, signal amplification is automatically implemented following delayed release of enhancement solution induced by water-soluble polyvinyl alcohol tape. As the polyvinyl alcohol tape is exposed to water, its polymer structure is perturbed (within 5 min), allowing ions to pass through. This new sensor was designed to have a short time delay between the flow of solutions used for the immunoassay and signal amplification. The α-trapLFI was subsequently used to detect cortisol with high sensitivity (9.1 pg∙mL^-1) over a broad detection range (0.01-1000 ng∙mL^-1) in bodily fluids. Furthermore, an excellent correlation was obtained by analyzing 20 human real saliva samples using this sensor and a conventional ELISA (R² = 0.90). The new sensor will be helpful in detecting various small molecules for simple, rapid, and portable POC diagnosis of stress disorders.

Low-cost, open-source 3D printed antibody dispenser for development and small-scale production of lateral flow assay strips

We present a low cost, 3D printed open-source antibody dispenser that can be easily built and used for the development of lateral flow assay (LFA) strips. The fabrication of LFA strips need dispensing of antibodies or antigens in a linear fashion and commercially available dispensers typically cost from few thousands to few tens of thousands of US dollars. In this paper, an antibody dispenser was built by using 3D printed and commercially available parts, which cost no more than 30 USD. This paper presents a detailed instruction on how to assemble the printer and how to achieve a specific line width for the dispensed antibody. By using syringe needles of different gauges, line width ranging from 0.23 to 1.8 mm can be dispensed, and by varying the speed controller, the dispensing needle's speed can be varied between 2.8 and 3.8 cm/s. We demonstrate uniform dispensing of anti-C-reactive protein (CRP) antibody and anti-rabbit antibody to draw a test line and a control line, which are used for the detection of CRP. The dispenser can also be equipped with two dispensing needles to allow simultaneous dispensing of multiple reagents, which can be useful for LFA strip development.

Dual aptamer assay for detection of Acinetobacter baumannii on an electromagnetically-driven microfluidic platform

Rapid detection of Acinetobacter baumannii (AB) is critical for limiting healthcare-associated infections and providing the best treatment for infected individuals. Herein an integrated microfluidic device for AB diagnosis utilizing a new dual aptamer assay was developed for point-of-care (POC) applications; magnetic beads coated with AB-specific aptamers were used to capture bacteria, and quantum dots (QD) bound to a second aptamer were utilized to quantify the amount of bacteria with a light-emitting diode (LED)-induced fluorescence module integrated into the device. Within a rapid detection of 30 min, a limit of detection of only 100 colony-forming units (CFU)/reaction was obtained, and all necessary microfluidic devices were actuated by a combination of permanent magnets and electromagnets. The pumping rate of the micropump was 270 μL/min at only 10 V, which is amenable for POC applications with lower power consumption, and only 10 μL of sample and reagents were required. Given these attributes, an automatic POC device was demonstrated which could perform a dual aptamer assay to diagnose AB by using electromagnetically-driven microfluidic system. This system provides a rapid, sensitive, low power and reagents consumption and fully automated for AB detection by using a dual aptamer assay. It will allow rapid clinical diagnosis of AB in the near future.

Pt-Ni(OH)2 nanosheets amplified two-way lateral flow immunoassays with smartphone readout for quantification of pesticides

Excessive use of herbicide and insecticide causes bioaccumulation in the environment and increases potential toxicity for people and animals. Portable systems for rapid assays of herbicide and insecticide residues have attracted prominent interests. Here, we developed a two-dimensional (2D) Pt-Ni(OH)₂ nanosheets (NSs) amplified two-way lateral flow immunoassay (LFI) with a smartphone-based readout for simultaneous detection of acetochlor and fenpropathrin. The 2D Pt-Ni(OH)₂ NSs were synthesized and used as the enhanced signal label in the immunoassay due to their high peroxidase-like activity and low migration speed. The two-way LFI was designed to eliminate potential cross-reaction between two targets. Portable detection system was developed based on a smartphone-based readout, which scans the LFI and provides the accurate testing result. The universal use of smartphones makes the developed platform suitable for cheap and on-site applications. Using the integrated platform, detection of acetochlor and fenpropathrin simultaneously was successfully achieved with the detection limits of 0.63 ng/mL and 0.24 ng/mL, respectively. To confirm the performance of the on-site application, we detected 10 non-spiked samples and 3 spiked samples. The obtained detection results were consistent with the data from gas chromatography analysis. The estimated recoveries ranged from 97.12% to 111.46%, indicating the practical reliability of our developed assay. The developed smartphone-based platform exhibits enhanced sensitivity, which provides a promising technique for on-site, multiplex, highly sensitive detection of pesticides.

The Application of Lipid Membranes in Biosensing

The exploitation of lipid membranes in biosensors has provided the ability to reconstitute a considerable part of their functionality to detect trace of food toxicants and environmental pollutants. This paper reviews recent progress in biosensor technologies based on lipid membranes suitable for food quality monitoring and environmental applications. Numerous biosensing applications based on lipid membrane biosensors are presented, putting emphasis on novel systems, new sensing techniques, and nanotechnology-based transduction schemes. The range of analytes that can be currently using these lipid film devices that can be detected include, insecticides, pesticides, herbicides, metals, toxins, antibiotics, microorganisms, hormones, dioxins, etc. Technology limitations and future prospects are discussed, focused on the evaluation/validation and eventually commercialization of the proposed lipid membrane-based biosensors.

A nitrocellulose membrane-based integrated microfluidic system for bacterial detection utilizing magnetic-composite membrane microdevices and bacteria-specific aptamers

Bacteria such as Acinetobacter baumannii (AB) can cause serious infections, resulting in high mortality if not diagnosed early and treated properly; there is consequently a need for rapid and accurate detection of this bacterial species. Therefore, we developed a new, nitrocellulose-based microfluidic system featuring AB-specific aptamers capable of automating the bacterial detection process via the activity of microfluidic devices composed of magnetic-composite membranes. Electromagnets were used to actuate these microfluidic devices such that the entire diagnostic process could be conducted in the integrated microfluidic system within 40 minutes with a limit of detection as low as 450 CFU per reaction for AB. Aptamers were used to capture AB in complex samples on nitrocellulose membranes, and a simple colorimetric assay was used to estimate bacterial loads. Given the ease of use, portability, and sensitivity of this aptamer-based microfluidic system, it may hold great promise for point-of-care diagnostics.

Detection of contaminants in water supply: A review on state-of-the-art monitoring technologies and their applications

Water monitoring technologies are widely used for contaminants detection in wide variety of water ecology applications such as water treatment plant and water distribution system. A tremendous amount of research has been conducted over the past decades to develop robust and efficient techniques of contaminants detection with minimum operating cost and energy. Recent developments in spectroscopic techniques and biosensor approach have improved the detection sensitivities, quantitatively and qualitatively. The availability of in-situ measurements and multiple detection analyses has expanded the water monitoring applications in various advanced techniques including successful establishment in hand-held sensing devices which improves portability in real-time basis for the detection of contaminant, such as microorganisms, pesticides, heavy metal ions, inorganic and organic components. This paper intends to review the developments in water quality monitoring technologies for the detection of biological and chemical contaminants in accordance with instrumental limitations. Particularly, this review focuses on the most recently developed techniques for water contaminant detection applications. Several recommendations and prospective views on the developments in water quality assessments will also be included.

Multiplexed Detection of Foodborne Pathogens from Contaminated Lettuces Using a Handheld Multistep Lateral Flow Assay Device

This paper presents a handheld device that is capable of simplifying multistep assays to perform sensitive detection of foodborne pathogens. The device is capable of multiplexed detection of Escherichia coli (E. coli) O157:H7, Salmonella Typhimurium (S. Typhimurium), Staphylococcus aureus, and Bacillus cereus. The limit of detection for each bacterium was characterized, and then, the detection of bacteria from contaminated fresh lettuces was demonstrated for two representative foodborne pathogens. We employed a sample pretreatment protocol to recover and concentrate target bacteria from contaminated lettuces, which can detect 1.87 × 104 CFU of E. coli O157:H7 and 1.47 × 104 CFU of S. Typhimurium/1 g of lettuce without an enrichment process. Lastly, we demonstrated that the limit of detection can be reduced to 1 CFU of E. coli O157:H7 and 1 CFU of S. Typhimurium/1 g of lettuce by including a 6 h enrichment of contaminated lettuces in growth media before pretreatment.

Nanozyme-Mediated Dual Immunoassay Integrated with Smartphone for Use in Simultaneous Detection of Pathogens

Nanozymes are an excellent class of optical reporters for the development of sensitive biosensors for widespread applications. In this study, mesoporous core-shell palladium@platinum (Pd@Pt) nanoparticles were synthesized and then applied as signal amplifier in a dual lateral flow immunoassay (LFIA) and integrated with a smartphone-based device for use in simultaneous detection of Salmonella Enteritidis and Escherichia coli O157:H7. After optimization, the limit of detections were calculated to be ∼20 cfu/mL for S. Enteritidis and ∼34 cfu/mL for E. coli O157:H7, respectively. The greatly improved sensitivity was contributed by the peroxidase-like catalytic activity of the Pd@Pt nanoparticles for signal enhancement and the parallel design of dual detection for eliminating the cross-interference. The estimated recoveries of the dual LFIA range from 91.44 to 117.00%, which indicated that the developed method is capable of detecting live bacteria in food samples. This approach provides an attractive platform for S. Enteritidis and E. coli O157:H7 detection using a smartphone-based device as the sole piece of equipment, indicating great promise for foodborne pathogen analysis or in-field food safety tracking.

Cell-SELEX Based Identification of an RNA Aptamer for Escherichia coli and Its Use in Various Detection Formats

Escherichia coli are important indicator organisms, used routinely for the monitoring of water and food safety. For quick, sensitive and real-time detection of E. coli we developed a 2'F modified RNA aptamer Ec3, by Cell-SELEX. The 31 nucleotide truncated Ec3 demonstrated improved binding and low nano-molar affinity to E. coli. The aptamer developed by us out-performs the commercial antibody and aptamer used for E. coli detection. Ec3(31) aptamer based E. coli detection was done using three different detection formats and the assay sensitivities were determined. Conventional Ec3(31)-biotin-streptavidin magnetic separation could detect E. coli with a limit of detection of 1.3 × 106 CFU/ml. Although, optical analytic technique, biolayer interferometry, did not improve the sensitivity of detection for whole cells, a very significant improvement in the detection was seen with the E. coli cell lysate (5 × 104 CFU/ml). Finally we developed Electrochemical Impedance Spectroscopy (EIS) gap capacitance biosensor that has detection limits of 2 × 104 CFU/mL of E. coli cells, without any labeling and signal amplification techniques. We believe that our developed method can step towards more complex and real sample application.

Gold nanoparticle-labeled biosensor for rapid and sensitive detection of bacterial pathogens

BACKGROUND

Escherichia coli O157:H7 is one of the major foodborne bacterial pathogens and also a biodefense agent. To ensure food safety and public health, it is very important to develop rapid methods for E. coli O157:H7 detection. In this study, we designed a nanoparticle-labeled biosensor for the rapid detection of E. coli O157:H7 in broth.

RESULTS

Magnetic nanoparticles (MNPs) were conjugated with monoclonal antibodies (Abs) to separate target E. coli O157:H7 cells from broth samples. Gold nanoparticles (AuNPs) were conjugated with polyclonal Abs, and were then introduced to the MNP-target complex to form a sandwich MNP-target-AuNP. By measuring the amount of AuNPs through an electrochemical method, the presence and the amount of the target bacteria were determined. Results showed a sensitivity of 10(1) colony forming units per milliliter (cfu/ml) with a linear range of 10(1)-10(6) cfu/ml.

CONCLUSIONS

Compared to conventional culture plating methods, the biosensor reduced the detection time from 2 to 4 days to less than 1 hour with a simple target extraction method. The AuNP-labeled biosensor has potential applications in the rapid detection of infectious agents for public health, biodefense, and food/water safety.

A Review of Membrane-Based Biosensors for Pathogen Detection

Biosensors are of increasing interest for the detection of bacterial pathogens in many applications such as human, animal and plant health, as well as food and water safety. Membranes and membrane-like structures have been integral part of several pathogen detection platforms. Such structures may serve as simple mechanical support, function as a part of the transduction mechanism, may be used to filter out or concentrate pathogens, and may be engineered to specifically house active proteins. This review focuses on membrane materials, their associated biosensing applications, chemical linking procedures, and transduction mechanisms. The sensitivity of membrane biosensors is discussed, and the state of the field is evaluated and summarized.

Estimation of Listeria monocytogenes and Escherichia coli O157:H7 prevalence and levels in naturally contaminated rocket and cucumber samples by deterministic and stochastic approaches

The aims of the present study were to determine the prevalence and levels of Listeria monocytogenes and Escherichia coli O157:H7 in rocket and cucumber samples by deterministic (estimation of a single value) and stochastic (estimation of a range of values) approaches. In parallel, the chromogenic media commonly used for the recovery of these microorganisms were evaluated and compared, and the efficiency of an enzyme-linked immunosorbent assay (ELISA)-based protocol was validated. L. monocytogenes and E. coli O157:H7 were detected and enumerated using agar Listeria according to Ottaviani and Agosti plus RAPID' L. mono medium and Fluorocult plus sorbitol MacConkey medium with cefixime and tellurite in parallel, respectively. Identity was confirmed with biochemical and molecular tests and the ELISA. Performance indices of the media and the prevalence of both pathogens were estimated using Bayesian inference. In rocket, prevalence of both L. monocytogenes and E. coli O157:H7 was estimated at 7% (7 of 100 samples). In cucumber, prevalence was 6% (6 of 100 samples) and 3% (3 of 100 samples) for L. monocytogenes and E. coli O157:H7, respectively. The levels derived from the presence-absence data using Bayesian modeling were estimated at 0.12 CFU/25 g (0.06 to 0.20) and 0.09 CFU/25 g (0.04 to 0.170) for L. monocytogenes in rocket and cucumber samples, respectively. The corresponding values for E. coli O157:H7 were 0.59 CFU/25 g (0.43 to 0.78) and 1.78 CFU/25 g (1.38 to 2.24), respectively. The sensitivity and specificity of the culture media differed for rocket and cucumber samples. The ELISA technique had a high level of cross-reactivity. Parallel testing with at least two culture media was required to achieve a reliable result for L. monocytogenes or E. coli O157:H7 prevalence in rocket and cucumber samples.

Novel strategies to enhance lateral flow immunoassay sensitivity for detecting foodborne pathogens

Food contaminated by foodborne pathogens causes diseases, affects individuals, and even kills those affected individuals. As such, rapid and sensitive detection methods should be developed to screen pathogens in food. One current detection method is lateral flow immunoassay, an efficient technique because of several advantages, including rapidity, simplicity, stability, portability, and sensitivity. This review presents the format and principle of lateral flow immunoassay strip and the development of conventional lateral flow immunoassay for detecting foodborne pathogens. Furthermore, novel strategies that can be applied to enhance the sensitivity of lateral flow immunoassay to detect foodborne pathogens are presented; these strategies include innovating new label application, designing new formats of lateral flow immunoassay, combining with other methods, and developing signal amplification systems. With these advancements, detection sensitivity and detection time can be greatly improved.

A novel enzyme-linked immunosorbent assay for detection of Escherichia coli O157:H7 using immunomagnetic and beacon gold nanoparticles

This paper presents a functional nanoparticle-enhanced enzyme-linked immunosorbent assay (FNP-ELISA) for detection of enterohemorrhagic Escherichia coli (EHEC) O157:H7. Immunomagnetic nanoparticles (IMMPs) conjugated with monoclonal anti-O157:H7 antibody were used to capture E. coli O157:H7. Beacon gold nanoparticles (B-GNPs) coated with polyclonal anti-O157:H7 and biotin single-stranded DNA (B-DNA) were then subjective to immunoreaction with E. coli O157:H7, which was followed by streptavidin-horseradish peroxidase (Strep-HRP) conjugated with B-GNPs based on a biotin-avidin system. The solutions containing E. coli O157:H7, IMMPs, B-GNPs, and Strep-HRP were collected for detecting color change. The signal was significantly amplified with detection limits of 68 CFU mL^-1 in PBS and 6.8 × 10² to 6.8 × 10³ CFU mL^-1 in the food samples. The FNP-ELISA method developed in this study was two orders of magnitude more sensitive than immunomagnetic separation ELISA (IMS-ELISA) and four orders of magnitude more sensitive than C-ELISA. The entire detection process of E. coli O157:H7 lasted only 3 h, and thus FNP-ELISA is considered as a time-saving method.

Development of automated paper-based devices for sequential multistep sandwich enzyme-linked immunosorbent assays using inkjet printing

To the best of our knowledge, this is the first report on paper-based devices for automating the sequential multistep procedures of a sandwich-type enzyme-linked immunosorbent assay (ELISA) that require only a single-step application of the sample solution. The device was based on a piece of nitrocellulose (NC) membrane with specially designed channels, where all the reagents are applied at different locations in order to control the fluid travel to the detection region. The inkjet printing method, a simple and low-cost process, was used to create the flow channel and device barrier patterns. The fabricated barrier was found to be an efficient boundary for the liquid along the printed design in the NC membrane, enabling direct control of the reagent flow time. ELISA results were obtained with a single-step sample application. The developed devices (so-called automated paper-based devices) provided a simple procedure for the sandwich ELISA, while reducing assay time and reagent consumption. Colorimetric results were measured using digital camera imaging with software processing. The capability of the method developed herein was successfully used to determine the levels of human chorionic gonadotropin (hCG) by ELISA.

Rapid affinity immunochromatography column-based tests for sensitive detection of Clostridium botulinum neurotoxins and Escherichia coli O157

Existing methods for detection of food-borne pathogens and their toxins are frequently time-consuming, require specialized equipment, and involve lengthy culture procedures and/or animal testing and are thus unsuitable for a rapid response to an emergency public health situation. A series of simple and rapid affinity immunochromatography column (AICC) assays were developed to detect Clostridium botulinum neurotoxin types A, B, E, and F and Escherichia coli O157 in food matrices. Specifically, for milk, grape juice with peach juice, and bottled water, the detection limit for the botulinum neurotoxin type A complex was 0.5 ng. Use of this method with a 10-ml sample would therefore result in a detection limit of 50 pg ml(-l). Thus, this assay is approximately 2 orders of magnitude more sensitive than a comparable lateral-flow assay. For botulinum neurotoxin complex types B, E, and F, the minimum detection limit was 5 ng to 50 ng. Sensitive detection of E. coli O157 was achieved, and the detection limit was 500 cells. The AICC test was also shown to be specific, rapid, and user friendly. This test takes only 15 to 30 min to complete without any specialized equipment and thus is suitable for use in the field. It has the potential to replace existing methods for presumptive detection of botulinum neurotoxin types A, B, E, and F and E. coli O157 in contaminated matrices without a requirement for preenrichment.