Development and evaluation of a highly sensitive immunochromatographic strip test using gold nanoparticle for direct detection of Vibrio cholerae O139 in seafoodsamples

Rapid method for detection of Vibrio cholerae from drinking water with nanomaterials enhancing electrochemical biosensor

Cholera is a potentially fatal diarrheal disease caused by Vibrio cholerae and is spread to humans from contaminated food and water. In order to prevent spread of epidemic chlorea, the development of novel sensitive, selective, user-friendly, cost-effective and rapid detection systems to detect of V. cholerae are necessary. Therefore, in this study, it was aimed to develop a specific, electrochemical immunoassay with high selectivitiy and sensitivity for detection of V. cholerae from drinking water using in house synthesized Gold Nanoparticles (AuNPs). The synthesized AuNPs were characterized by UV/Vis spectroscopy, Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM) and electrochemical techniques were applied to confirm the succesful fabrication of the immunosensor. Also, this study focuses on the development of an antibody sensor for V. cholerae detection using a standard immunoassay without using nanoparticle. To accomplish that, in house spherical synthesized AuNPs at various sizes were synthesized, conjugated with secondary antibody-horseradish peroxidase enzyme (HRP) complex and their possible effect on the lowest detection limit of V. cholerae was investigated in comparison to commercially available AuNPs. The AuNPs-immunosensor on the results enabled the quantification of V. cholerae in a wide concentration range with a high sensitivity limit of detection (1 Colony-Forming Units/Milliliter) and specificity. Although the effect of 33 and 54 nm AuNPs on the process is close to each other, it has been observed that there is a 34% loss of efficiency when the size of the nanoparticle increases. With this study, a novel V. cholerae specific immunosensor was developed and the effects of in house synthesized AuNPs with various diameter on this developed biosensor were investigated in detail.

Development of lectin-based lateral flow assay for fucosylated alpha-fetoprotein

Fucosylated alpha-fetoprotein (AFP-L3) is a more specific and sensitive biomarker for early diagnosis of hepatocellular carcinoma (HCC) than only the alpha-fetoprotein (AFP) level. Rapid and simple detection of AFP-L3 level greatly facilitates the early detection as well as the treatment of HCC, resulting in the reduction of mortality. Here, we developed a rapid and sensitive lateral flow assay (LFA) using lectin Lens culinaris agglutinin (LCA), which has a specific affinity to AFP-L3 fraction of AFP, as a biorecognition element for determination of the fucosylation of AFP. The assay is based on a sandwich format performed on a lateral flow test strip. LCA was immobilized on the membrane as a test line (T). Quantitative detection of AFP-L3 was achieved by measuring the green color intensity of captured gold nanoparticle conjugates on the T and control line (C) utilizing an in-house test strip reader. The calculated absorbance obtained by the green color intensity signals proportionally increased with AFP concentrations. The developed lectin-based LFA provided a detection limit of 0.8 ng/mL for AFP with a linear range between 1.5 and 160.0 ng/mL within an assay time of 10 min. Recoveries between 74.5% and 113.2% with relative standard deviations of 5.2%-8.7% for measuring spiked human serum were also achieved. The results reveal that the proposed assay offers a rapid, sensitive, and specific method, which is useful for development in point-of-care testing for early detection and treatment of HCC.

A review of rapid food safety testing: using lateral flow assay platform to detect foodborne pathogens

The detrimental impact of foodborne pathogens on human health makes food safety a major concern at all levels of production. Conventional methods to detect foodborne pathogens, such as live culture, high-performance liquid chromatography, and molecular techniques, are relatively tedious, time-consuming, laborious, and expensive, which hinders their use for on-site applications. Recurrent outbreaks of foodborne illness have heightened the demand for rapid and simple technologies for detection of foodborne pathogens. Recently, Lateral flow assays (LFA) have drawn attention because of their ability to detect pathogens rapidly, cheaply, and on-site. Here, we reviewed the latest developments in LFAs to detect various foodborne pathogens in food samples, giving special attention to how reporters and labels have improved LFA performance. We also discussed different approaches to improve LFA sensitivity and specificity. Most importantly, due to the lack of studies on LFAs for the detection of viral foodborne pathogens in food samples, we summarized our recent research on developing LFAs for the detection of viral foodborne pathogens. Finally, we highlighted the main challenges for further development of LFA platforms. In summary, with continuing improvements, LFAs may soon offer excellent performance at point-of-care that is competitive with laboratory techniques while retaining a rapid format.

Development of a rapid immunochromatographic strip test for the detection of Vibrio parahaemolyticus toxin B that cause acute hepatopancreatic necrosis disease

Here, two monoclonal antibodies (MAbs) specific to different epitopes on ToxB, a toxin produced by Vibrio parahaemolyticus that causes acute hepatopancreatic necrosis disease (VP_AHPND ), were employed to develop a rapid strip test. One MAb was conjugated to colloidal gold to bind to ToxB at the application pad, and another MAb was used to capture colloidal gold MAb-protein complexes at the test line (T) on the nitrocellulose strip. To validate test performance, a downstream control line (C) of goat anti-mouse immunoglobulin G antibody was used to capture the free colloidal gold conjugate MAb. The sample in the application buffer could be applied directly to the application well, and the test result was obtained within 15 min. The sensitivity of the kit is approximately 6.25 µg/ml of toxin, which was equivalent to the toxin produced by approximately 10⁷  cfu/ml of bacteria. This kit is convenient and easy to use since it can be used to identify VP_AHPND directly using a single colony of bacteria grown on agar culture plates. Because of its high specificity and simplicity, as well as not being reliant on sophisticated equipment or specialized skills, this strip test could be used by farmers for surveillance for ToxB-producing bacteria.

Development of a colloidal gold strip-based immunochromatographic assay for rapid detection of Fusarium oxysporum in ginger

BACKGROUND

Rhizome rot, caused primarily by Fusarium oxysporum, is one of the most destructive diseases leading to significant loss in ginger worldwide. The loss can be greatly reduced by proper disease management practices steered by accurate and early diagnosis of pathogens. Pathogen detection at an early stage of infection can also reduce the incidence of disease epidemics. Classical methods are often time consuming, relying on culturing the putative pathogens and the availability of expert taxonomic skills for accurate identification, which leads to the delayed application of control measures. The development of a simple, rapid, sensitive and cost-effective point-of-care diagnostic tool is thus one of the major research priorities for rhizome rot.

RESULTS

The 65 kDa, immunoreactive protein band was selected as a diagnostic marker and was subjected to MS analysis followed by blastp. Based on blast result, a synthetic antigenic peptide was synthesized, and used to generate pAbs. The peptide-specific antibodies were used to develop a colloidal gold immunochromatographic assay (ICA). The sensitivity, specificity, and accuracy of ICA were 92.59%, 81.25%, and 90%, respectively. The ICA has a visual detection limit of 2.122 μg mL-1 for infected rhizome samples and 5.065 μg mL-1 for leaf samples with optimal detection time within 5 min. Moreover, the ICA also detected early stage infected samples, of which 71.42% (50/70) were true positives.

CONCLUSION

Findings from this study indicated that the assay can be utilized as a tool for the investigation of rhizome rot infection in field samples. © 2019 Society of Chemical Industry.

Plasmonic enhancement in lateral flow sensors for improved sensing of E. coli O157:H7

We propose a plasmonic enhanced lateral flow sensor (pLFS) concept with an enhanced colorimetric signal by utilizing liposome encapsulating reagent to trigger the aggregation of gold nanoparticles (GNPs). Our signal enhancement strategy incorporates the simplicity of lateral flow immunoassays (LFIA) utilizing plasmonic enhancement. The conceptualized hybrid pLFS for onsite rapid detection of pathogens in low numbers in a user friendly format requiring simple steps is the first step in the translation of plasmonic enhancement sensing to a practical regime. The pLFS was carried out with a biotinylated liposome label ruptured to release branched polyethylenimine (BPEI) to trigger the aggregation of GNPs for colorimetric signal generation. BPEI has multiple amino groups and more positive charges in PBS buffer, therefore few of the BPEI groups could induce the aggregation of GNPs, resulting in an enhanced colorimetric signal to detect E. coli O157:H7. Compared with the reported conventional LFIA, the proposed pLFS demonstrated more than 1000-fold improvement in sensitivity. The pLFS could detect as low as 100 CFU/ml of E. coli O157:H7 in buffer and 600 CFU/ml E. coli O157:H7 in liquid food systems.

Paper-based lateral flow strip assay for the detection of foodborne pathogens: principles, applications, technological challenges and opportunities

As a representative colorimetic biosnesor, paper-based LFSA have emerged as a promising and robust tool that can easily and instansly detect the presence of target biological components in food sample. Recently, LFSAs have gained a considerable attention as an alternative method for rapid diagnosis of foodborne pathogens to the conventional culture-based assays such as plate counting and PCR. One major drawback of the current LFSAs for the detection of pathogenic bacteria is the low sensitivity, limiting its practical applications in POCT. Not like many other protein-based biomarkers that are present in nM or pM range, the number of pathogenic bacteria that cause disease can be as low as few CFU/ml. Here, we review current advances in LFSAs for the detection of pathogenic bacteria in terms of chromatic agents and analyte types. Furthermore, recent approaches for signal enhancement and modifications of the LFSA architecture for multiplex detection of pathogenic bacteria are included in this review, together with the advantages and limitations of each techniques. Finally, the technological challenges and future prospect of LFSA-based POCT for the detection of pathogenic bacteria are discussed.

A 3D-Printed Millifluidic Platform Enabling Bacterial Preconcentration and DNA Purification for Molecular Detection of Pathogens in Blood

Molecular detection of pathogens in clinical samples often requires pretreatment techniques, including immunomagnetic separation and magnetic silica-bead-based DNA purification to obtain the purified DNA of pathogens. These two techniques usually rely on handling small tubes containing a few millilitres of the sample and manual operation, implying that an automated system encompassing both techniques is needed for larger quantities of the samples. Here, we report a three-dimensional (3D)-printed millifluidic platform that enables bacterial preconcentration and genomic DNA (gDNA) purification for improving the molecular detection of target pathogens in blood samples. The device consists of two millichannels and one chamber, which can be used to preconcentrate pathogens bound to antibody-conjugated magnetic nanoparticles (Ab-MNPs) and subsequently extract gDNA using magnetic silica beads (MSBs) in a sequential manner. The platform was able to preconcentrate very low concentrations (1–1000 colony forming units (CFU)) of Escherichia coli O157:H7 and extract their genomic DNA in 10 mL of buffer and 10% blood within 30 min. The performance of the platform was verified by detecting as low as 1 CFU of E. coli O157:H7 in 10% blood using either polymerase chain reaction (PCR) with post gel electrophoresis or quantitative PCR. The results suggest that the 3D-printed millifluidic platform is highly useful for lowering the limitations on molecular detection in blood by preconcentrating the target pathogen and isolating its DNA in a large volume of the sample.

Comparison of two different combined test strips with fluorescent microspheres or colored microspheres as tracers for rotavirus and adenovirus detection

Background

Rotavirus (RV) and enteric adenovirus (AdV) mainly cause infantile infectious gastroenteritis. Several separate test methods for the detection of RV or AdV are currently available, but few tests are able to simultaneously detect both RV and AdV viruses, especially in primary medical institutions.

Methods

The present study was mainly designed to compare the performance of two combined test strips for the detection of RV and AdV: a rotavirus–adenovirus strip with fluorescent microspheres for tracers (FMT); and the CerTest rotavirus–adenovirus blister strip with colored microspheres for tracers (CMT). To test the strips cultures of RV, AdV and from other enteric pathogens were used, in addition to 350 stool specimens from 45 symptomatic patients with gastrointestinal infections.

Results

Detection thresholds for RV and AdV cultures using serial dilutions showed that the sensitivity of FMT was significantly higher than that of CMT (both P < 0.05). Specificity evaluation demonstrated that with culture mixtures of Coxsackie (A16), ECHO (type30), and entero- (EV71) viruses there was no detection of cross reaction using the two test strips, i.e., all the results were negative. With regard to the detection of RV in 350 clinical specimens, the total coincidence rate was 92.9%, the positive coincidence rate was 98.2%, and the negative coincidence rate was 90.8%. With regard to AdV detection, the total coincidence rate was 95.4%, the positive coincidence rate was 95.2%, and the negative coincidence rate was 95.5%.

Conclusions

FMT performed better than CMT with regard to the combined detection of RV and AdV.

Recent advances in nanoparticle-based lateral flow immunoassay as a point-of-care diagnostic tool for infectious agents and diseases

Recent advances in lateral flow immunoassay-based devices as a point-of-care analytical tool for the detection of infectious diseases are reviewed.

Ultrasensitive Biosensor for the Detection of Vibrio cholerae DNA with Polystyrene-co-acrylic Acid Composite Nanospheres

An ultrasensitive electrochemical biosensor for the determination of pathogenic Vibrio cholerae (V. cholerae) DNA was developed based on polystyrene-co-acrylic acid (PSA) latex nanospheres-gold nanoparticles composite (PSA-AuNPs) DNA carrier matrix. Differential pulse voltammetry (DPV) using an electroactive anthraquninone oligonucleotide label was used for measuring the biosensor response. Loading of gold nanoparticles (AuNPs) on the DNA-latex particle electrode has significantly amplified the faradaic current of DNA hybridisation. Together with the use of a reported probe, the biosensor has demonstrated high sensitivity. The DNA biosensor yielded a reproducible and wide linear response range to target DNA from 1.0 × 10-21 to 1.0 × 10-8 M (relative standard deviation, RSD = 4.5%, n = 5) with a limit of detection (LOD) of 1.0 × 10-21 M (R 2 = 0.99). The biosensor obtained satisfactory recovery values between 91 and 109% (n = 3) for the detection of V. cholerae DNA in spiked samples and could be reused for six consecutive DNA assays with a repeatability RSD value of 5% (n = 5). The electrochemical biosensor response was stable and maintainable at 95% of its original response up to 58 days of storage period.

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.

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.

Development and evaluation of an up-converting phosphor technology-based lateral flow assay for the rapid, simultaneous detection of Vibrio cholerae serogroups O1 and O139

Vibrio cholerae serogroups O1 and O139 are etiological agents of cholera, a serious and acute diarrheal disease, and rapid detection of V. cholerae is a key method for preventing and controlling cholera epidemics. Here, a point of care testing (POCT) method called Vch-UPT-LF, which is an up-converting phosphor technology-based lateral flow (UPT-LF) assay with a dual-target detection mode, was developed to detect V. cholerae O1 and O139 simultaneously from one sample loading. Although applying an independent reaction pair made both detection results for the two Vch-UPT-LF detection channels more stable, the sensitivity slightly declined from 104 to 105 colony-forming units (CFU) mL-1 compared with that of the single-target assay, while the quantification ranges covering four orders of magnitude were maintained. The strip showed excellent specificity for seven Vibrio species that are highly related genetically, and nine food-borne species whose transmission routes are similar to those of V. cholerae. The legitimate arrangement of the two adjacent test lines lessened the mutual impact of the quantitation results between the two targets, and the quantification values did not differ by more than one order of magnitude when the samples contained high concentrations of both V. cholerae O1 and O139. Under pre-incubation conditions, 1×101 CFU mL-1 of V. cholerae O1 or O139 could be detected in fewer than 7 h, while the Vch-UPT-LF assay exhibited sensitivity as high as a real-time fluorescent polymerase chain reaction with fewer false-positive results. Therefore, successful development of Vch-UPT-LF as a dual-target assay for quantitative detection makes this assay a good candidate POCT method for the detection and surveillance of epidemic cholera.

Point-of-care test for cervical cancer in LMICs

Cervical cancer screening using Papanicolaou's smear test has been highly effective in reducing death from this disease. However, this test is unaffordable in low- and middle-income countries, and its complexity has limited wide-scale uptake. Alternative tests, such as visual inspection with acetic acid or Lugol's iodine and human papillomavirus DNA, are sub-optimal in terms of specificity and sensitivity, thus sensitive and affordable tests with high specificity for on-site reporting are needed. Using proteomics and bioinformatics, we have identified valosin-containing protein (VCP) as differentially expressed between normal specimens and those with cervical intra-epithelial neoplasia grade 2/3 (CIN2/CIN3+) or worse. VCP-specific immunohistochemical staining (validated by a point-of-care technology) provided sensitive (93%) and specific (88%) identification of CIN2/CIN3+ and may serve as a critical biomarker for cervical-cancer screening. Future efforts will focus on further refinements to enhance analytic sensitivity and specificity of our proposed test, as well as on prototype development.

Ultrasensitive detection of microbial cells using magnetic focus enhanced lateral flow sensors

We report on an improved lateral flow immunoassay (LFIA) sensor with a magnetic focus for ultrasensitive naked-eye detection of pathogenic microorganisms at a near single cell limit without any pre-enrichment steps, by allowing the magnetic probes to focus the labelled pathogens to the target zone of the LF strip.

A novel immunochromatographic assay based on a time-resolved chemiluminescence strategy for the multiplexed detection of ractopamine and clenbuterol

A novel multiplexed immunochromatographic assay (ICA) based on a time-resolved chemiluminescence (CL) strategy was developed for quantitative detection of β-agonists, by utilizing ractopamine (RAC) and clenbuterol (CLE) as the models. Different from conventional multiplexed ICA methods which usually require two or more test lines, this strategy was developed for detection of two β-agonists by using only one test line on the nitrocellulose membrane. In this study, horseradish peroxidase and alkaline phosphatase were used as the signal probes to label RAC antibody and CLE antibody, respectively. The two CL reactions with flash type and glow type kinetics characteristics were triggered simultaneously by injecting the coreactants, then the signals for RAC and CLE detections were recorded at 3 s and 300 s after coreactants injection, respectively. Owing to the utilization of CL detection, this protocol showed ideal sensitivity for quantitation. Under the optimal conditions, the detection limits for RAC and CLE were 0.17 ng mL(-1) and 0.067 ng mL(-1) (S/N = 3), respectively. The whole assay process can be accomplished within 20 min without complicated sample pretreatment. The proposed method was successfully applied for the detection of RAC and CLE in spiked swine urine. It opens up a new pathway for designing a low cost, time-efficiency and multiplexed strategy for rapid screening and field assay.

Novel polymeric nanoparticles targeting the lipopolysaccharides of Pseudomonas aeruginosa

Considering outburst of various infectious diseases globally, nanoparticle assisted targeted drug delivery has emerged as a promising strategy that can enhance the therapeutic efficacy and minimize the undesirable side effects of an antimicrobial agents. Molecular imprinting is a newly developed strategy that can synthesize a drug carrier with highly stable ligand-like 'cavity', may serve as a new platform of ligand-free targeted drug delivery systems. In this study, we use the amphiphilic lipopolysaccharides, derived from Pseudomonas aeruginosa as imprinting template and obtained an evenly distributed sub-40 nm polymeric nanoparticles by using inverse emulsion method. These molecularly imprinted nanoparticles (MIPNPs) showed specific binding to the lipopolysaccharide as determined by fluorescence polarization and microscale thermophoresis. MIPNPs showed selective recognition of target bacteria as detected by flow cytometry. Additionally, MIPNPs exhibited the in vivo targeting capabilities in both the keratitis model and meningitis model. Moreover, the photosensitizer methylene blue-loaded MIPNPs presented significantly strong inhibition of bacterial Growth, compared to non-imprinted controls for in vitro model of the photodynamic therapy. Our study shows an attempt to design a magic bullet by molecular imprinting that may provide a novel approach to generate synthetic carrier for targeting pathogen and treatment for a variety of infectious human diseases.

Rapid and sensitive lateral flow immunoassay method for determining alpha fetoprotein in serum using europium (III) chelate microparticles-based lateral flow test strips

Alpha-fetoprotein (AFP), a primary marker for many diseases including various cancers, is important in clinical tumor diagnosis and antenatal screening. Most immunoassays provide high sensitivity and accuracy for determining AFP, but they are expensive, often complex, time-consuming procedures. A simple and rapid point-of-care system that integrates Eu (III) chelate microparticles with lateral flow immunoassay (LFIA) has been developed to determine AFP in serum with an assay time of 15 min. The approach is based on a sandwich immunoassay performed on lateral flow test strips. A fluorescence strip reader was used to measure the fluorescence peak heights of the test line (HT) and the control line (HC); the HT/HC ratio was used for quantitation. The Eu (III) chelate microparticles-based LFIA assay exhibited a wide linear range (1.0-1000 IU mL(-1)) for AFP with a low limit of detection (0.1 IU mL(-1)) based on 5ul of serum. Satisfactory specificity and accuracy were demonstrated and the intra- and inter-assay coefficients of variation (CV) for AFP were both <10%. Furthermore, in the analysis of human serum samples, excellent correlation (n = 284, r = 0.9860, p < 0.0001) was obtained between the proposed method and a commercially available CLIA kit. Results indicated that the Eu (III) chelate microparticles-based LFIA system provided a rapid, sensitive and reliable method for determining AFP in serum, indicating that it would be suitable for development in point-of-care testing.

Rapid pathogen detection by lateral-flow immunochromatographic assay with gold nanoparticle-assisted enzyme signal amplification

To date most LF-ICA format for pathogen detection is based on generating color signals from gold nanoparticle (AuNP) tracers that are perceivable by naked eye but often these methods exhibit sensitivity lower than those associated with the conventional enzyme-based immunological methods or mandated by the regulatory guidelines. By developing AuNP avidin-biotin constructs in which a number of enzymes can be labeled we report on an enhanced LF-ICA system to detect pathogens at very low levels. With this approach we show that as low as 100 CFU/mL of Escherichia coli O157:H7 can be detected, indicating that the limit of detection can be increased by about 1000-fold due to our signal amplification approach. In addition, extensive cross-reactivity experiments were conducted (19 different organisms were used) to test and successfully validate the specificity of the assay. Semi-quantitative analysis can be performed using signal intensities which were correlated with the target pathogen concentrations for calibration by image processing.

A novel dynamic flow immunochromatographic test (DFICT) using gold nanoparticles for the serological detection of Toxoplasma gondii infection in dogs and cats

A novel dynamic flow immunochromatographic test (DFICT) is proposed for rapid assay utilizing Toxoplasma gondii as a model. The test is based on a proprietary technology that combines the principles of immunochromatography and fluid dynamics. Gold nanoparticles conjugated to staphylococcal protein A (SPA) were prepared in liquid form and used as signal vehicles. T. gondii-specific recombinant antigens and SPA were sprayed onto a nitrocellulose membrane in strips at positions designated as T and C, respectively. The DFICT is performed by applying a 100 µL aliquot of liquid gold-SPA conjugate to the reagent hole and a 5 μL aliquot of serum sample to the sample hole. The results were observable within 5 min by the naked eye. The lowest detectable limit of the assay was determined as the highest dilution (1:320) of positive serum. No cross-reaction of the antibodies with other related canine or feline pathogens was observed. The DFICT can be stored for 12 months at 4 °C or 6 months with no loss of sensitivity or specificity. A high degree of consistency was observed between the DFICT and the standard ELISA kit, supporting the reliability of the novel test strip. The introduction of a liquid gold nanoparticle conjugate reagent provides this method with several attractive characteristics, such as ease of manufacture, low sample volume requirements, high selectivity and high efficiency. This method opens a novel pathway for rapid diagnostic screening and field analysis.

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A novel dynamic flow immunochromatographic test (DFICT) is developed.

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A liquid gold nanoparticle conjugate reagent is introduced in DFICT.

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It is not necessary to prepare the conjugated pad and the sample pad in DFICT.

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DFICT requires only 5 μL of serum sample with no need for sample pretreatment.

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DFICT can be used for serological detection of T. gondii in both dogs and cats.

Membrane filter-assisted surface enhanced Raman spectroscopy for the rapid detection of E. coli O157:H7 in ground beef

Consumption of food contaminated with Escherichia coli O157:H7 is one of the major concerns in ensuring food safety. Techniques that are simple and suitable for fast screening to detect and identify pathogens in the food chain is vital to ensure food safety. In this work, we propose a simple and rapid technique to detect low levels of E. coli O157:H7 using membrane filtration and silver intensification steps in combination with surface enhanced Raman spectroscopy (SERS) analysis. The target bacteria can be captured and separated efficiently by two different antibody bearing nanoparticle complexes (magnetic nanoparticles and gold nanoparticles with a Raman reporter). After centrifugal filtration, the bacteria-nanoparticle complexes left on the filter membrane were localized by silver intensification process before probing by SERS. Extremely low concentration of E. coli O157:H7 (~10 CFU/mL) could be detected within 1h and 3h from both pure culture and ground beef samples, respectively. This method can potentially be used as an effective pathogen screening tool for routine monitoring.

Nano/micro and spectroscopic approaches to food pathogen detection

Despite continuing research efforts, timely and simple pathogen detection with a high degree of sensitivity and specificity remains an elusive goal. Given the recent explosion of sensor technologies, significant strides have been made in addressing the various nuances of this important global challenge that affects not only the food industry but also human health. In this review, we provide a summary of the various ongoing efforts in pathogen detection and sample preparation in areas related to Fourier transform infrared and Raman spectroscopy, light scattering, phage display, micro/nanodevices, and nanoparticle biosensors. We also discuss the advantages and potential limitations of the detection methods and suggest next steps for further consideration.

Colloidal gold-based immunochromatographic strip test compromising optimised combinations of anti-S. suis capsular polysaccharide polyclonal antibodies for detection of Streptococcus suis

A rapid diagnosis kit that detects Streptococcus suis (S. suis) antigens from urine with an immunochromatographic stripe (ICS) test was developed in this study. The ICS test was produced using colloidal gold coated with polyclonal antibodies (pAbs) against S. suis. The pAbs were developed from rabbits immunised with S. suis serotype 2 capsular polysaccharides (CPS). Development of the pAbs was investigated to establish their binding to CPS and to determine the maximum sensitivity of two combination antibodies for the ICS test. The results of the ICS optimisation revealed that the combinations of pAb C-N1 and pAb C-N2 had the highest sensitivity to CPS. The minimum limitation of ICS sensitivity indicated 1.0 × 10(4) colony forming units (CFU) and a CPS concentration of 0.05 µg. The assay time for detection of S. suis antigens is less than 15 min, which is suitable for rapid detection. A cross-reactive test was also conducted, and it detected no other bacteria (Streptococcus pneumoniae, Streptococcus agalactiae, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae). The cross-reactivity of other serotypes in S. suis was also investigated, and tests for serotypes of 1, 1/2, 3, 4, 5, 6, 7, 8, 9, 14, and 16 were positive. This study presents the first report of a development of an ICS that enables the quantitative detection of streptococcal antigens. The S. suis ICS provides several advantages over other methods, including the speed and simplicity of use.