Development of colloidal gold-based immunochromatographic assay for rapid detection of Mycoplasma suis in porcine plasma

Development of a colloidal gold immunochromatographic strip for rapid detection of avian coronavirus infectious bronchitis virus

Avian infectious bronchitis virus (IBV) still causes serious economic losses in the poultry industry. Currently, there are multiple prevalent genotypes and serotypes of IBVs. It is imperative to develop a new diagnosis method that is fast, sensitive, specific, simple, and broad-spectrum. A monoclonal hybridoma cell, N2D5, against the IBV N protein was obtained after fusion of myeloma SP2/0 cells with spleen cells isolated from the immunized Balb/c mice. The N2D5 monoclonal antibody (mAb) and the previously prepared mouse polyclonal antibody against the IBV N protein were used to target IBV as a colloidal gold-mAb conjugate and a captured antibody, respectively, in order to develop an immunochromatographic strip. The optimal pH and minimum antibody concentration in the reaction system for colloidal gold-mAb N2D5 conjugation were pH 6.5 and 30 μg/mL, respectively. Common avian pathogens were tested to evaluate the specificity of the strip and no cross-reaction was observed. The sensitivity of the strip for detecting IBV was 10-1.4522 EID50/mL. The strip showed a broad-spectrum cross-reactive capacity for detecting IBV antigens, including multiple IBV genotypes in China and all of the seven serotypes of IBV that are currently prevalent in southern China. Additionally, the result can be observed within 2 min without any equipment. The throat and cloacal swab samples of chickens that were artificially infected with three IBV strains were tested using the developed strip and the qPCR method; the strip test demonstrated a high consistency in detecting IBV via qPCR gene detection. In conclusion, the immunochromatographic strip that was established is rapid, sensitive, specific, simple, practical, and broad-spectrum; additionally, it has the potential to serve as an on-site rapid detection method of IBV and can facilitate the surveillance and control of the disease, especially in resource-limited areas.

Carbon dots@noble metal nanoparticle composites: research progress report

Carbon dots@noble metal nanoparticle composites are formed by combining carbon dots and metal nanoparticles using various strategies. Carbon dots exhibit a reducing ability and function as stabilisers; consequently, metal-ion solutions can be directly reduced by them to synthesise gold, silver, and gold-silver alloy particles. Carbon dots@gold/silver/gold-silver particle composites have demonstrated the potential for several practical applications owing to their superior properties and simple preparation process. Until now, several review articles have been published to summarise fluorescent carbon dots or noble metal nanomaterials. Compared with metal-free carbon dots, carbon dots@noble metal nanoparticles have a unique morphology and structure, resulting in new physicochemical properties, which allow for sensing, bioimaging, and bacteriostasis applications. Therefore, to promote the effective development of carbon dots@noble metal nanoparticle composites, this paper primarily reviews carbon dots@gold/silver/gold-silver alloy nanoparticle composites for the first time in terms of the following aspects. (1) The synthesis strategies of carbon dots@noble metal nanoparticle composites are outlined. The principle and function of carbon dots in the synthesis strategies are examined. The advantages and disadvantages of these methods and composites are analysed. (2) The characteristics and properties of such composites are described. (3) The applications of these composite materials are summarised. Finally, the potentials and limitations of carbon dots@noble metal nanoparticle composites are discussed, thus laying the foundation for their further development.

Colloidal gold based immunochromatographic detection of Mycoplasmopsis synoviae infection and its prevalence in avian species of Karachi, Pakistan

Avian mycoplasmosis is an infection that commonly prevails in birds, particularly in poultry chickens. Among mycoplasmosis causing organisms, Mycoplasmopsis synoviae is a predominant and lethal pathogen to the aves. Considering the increased incidence of infections by M. synoviae, the prevalence of M. synoviae was deduced in poultry chickens and fancy birds of Karachi region. The lungs and tracheal samples from chicken and dead fancy birds and swab samples from live fancy birds were collected and investigated by amplifying 16 s rRNA gene of M. synoviae. Biochemical characteristics of M. synoviae was also evaluated. Furthermore, surface-associated membrane proteins, that represent key antigens for diagnosis of M. synoviae infection was extracted by Triton X- 114 method. Results showed that M. synoviae was detected more frequently in lungs than in trachea, that could be due to its invasion capacity and tissue affinity. SDS PAGE analysis of extracted membrane proteins showed two prominent hydrophobic proteins of different molecular mass including proteins of 150 and 50 kDa. Protein of 150 kDa was purified by size exclusion chromatography and it exhibited agglutinogen activity. Purified protein was used in the development of one-step immunochromatographic (ICT) assay for the detection of antibodies against M. synoviae using gold nanoparticles coated with polyclonal antibodies. Low levels of antibodies were detected by the developed ICT kit, which has 88% sensitivity with 92% specificity.

Establishment of molecular diagnostics targeting the 23S ribosomal RNA gene for the detection of Mycoplasma suis infection in Thai domestic pigs

Mycoplasma (M.) suis is a pathogenic hemotropic Mycoplasma sp. that causes acute hemolytic anemia or chronic infection in pigs. M. suis infection can be diagnosed using several methods, including molecular diagnosis such as conventional PCR (cPCR) and quantitative PCR (qPCR). In these cases, the common target is the 16S rRNA gene; however, this genetic marker cannot distinguish hemoplasma at the species level owing to high sequence identity. Therefore, the 23S rRNA gene has emerged as another target gene. Other than PCR, the loop-mediated isothermal amplification (LAMP) method can be applied for M. suis. The objective of the present study was to establish cPCR, TaqMan qPCR, and LAMP assays in which the 23S rRNA gene is used to detect M. suis infection in Thai domestic pigs. The analytical sensitivity of cPCR was determined as 7.46 × 10⁴ copies/μl of plasmid DNA, whereas those of qPCR and LAMP were 7.46 × 10² copies/μl. There was no cross reaction with other pathogens in any of the assays. To evaluate the diagnostic performance of the assays, they were tested using 173 samples of genomic DNA. The detection percentage of M. suis infection was 24.86% (43/173; 95% CI: 18.61%-31.89%), 28.32% (49/173; 95% CI: 21.75%-35.66%), and 29.48% (51/173; 95% CI: 22.80%-36.88%) using cPCR, qPCR, and LAMP, respectively. Using qPCR as a reference assay, cPCR showed 81.63% sensitivity, 97.58% specificity, and an almost perfect level of agreement (kappa = 0.823). In comparison, LAMP showed 77.55% sensitivity, 89.52% specificity, and a substantial level of agreement (kappa = 0.662). All assays tested here could be applied in veterinary diagnostic laboratories for monitoring porcine health in the herds. Furthermore, the LAMP assay could be used as a screening test in farm practice without the need for any special equipment.

Progress and Challenges of Point-of-Need Photonic Biosensors for the Diagnosis of COVID-19 Infections and Immunity

The new coronavirus disease, COVID-19, caused by SARS-CoV-2, continues to affect the world and after more than two years of the pandemic, approximately half a billion people are reported to have been infected. Due to its high contagiousness, our life has changed dramatically, with consequences that remain to be seen. To prevent the transmission of the virus, it is crucial to diagnose COVID-19 accurately, such that the infected cases can be rapidly identified and managed. Currently, the gold standard of testing is polymerase chain reaction (PCR), which provides the highest accuracy. However, the reliance on centralized rapid testing modalities throughout the COVID-19 pandemic has made access to timely diagnosis inconsistent and inefficient. Recent advancements in photonic biosensors with respect to cost-effectiveness, analytical performance, and portability have shown the potential for such platforms to enable the delivery of preventative and diagnostic care beyond clinics and into point-of-need (PON) settings. Herein, we review photonic technologies that have become commercially relevant throughout the COVID-19 pandemic, as well as emerging research in the field of photonic biosensors, shedding light on prospective technologies for responding to future health outbreaks. Therefore, in this article, we provide a review of recent progress and challenges of photonic biosensors that are developed for the testing of COVID-19, consisting of their working fundamentals and implementation for COVID-19 testing in practice with emphasis on the challenges that are faced in different development stages towards commercialization. In addition, we also present the characteristics of a biosensor both from technical and clinical perspectives. We present an estimate of the impact of testing on disease burden (in terms of Disability-Adjusted Life Years (DALYs), Quality Adjusted Life Years (QALYs), and Quality-Adjusted Life Days (QALDs)) and how improvements in cost can lower the economic impact and lead to reduced or averted DALYs. While COVID19 is the main focus of these technologies, similar concepts and approaches can be used and developed for future outbreaks of other infectious diseases.

Mycoplasma suis Alpha-Enolase Subunit Vaccine Induces an Immune Response in Experimental Animals

Recombinant protein technology has emerged as an excellent option for vaccine development. However, prior to our study, the immune induction ability of recombinant Mycoplasma suis alpha-enolase (rMseno) in animals remained unclear. The purpose of this study was to develop a rMseno protein subunit vaccine and to determine its ability to elicit an immunological response. To accomplish this, we cloned the gene into pET-15b, expressed it in BL21 cells, and purified it. Following the establishment of immunity, the immunogenicity and potential for protection of rMseno were evaluated in mice and piglets. The results demonstrate that anti-M. suis serum recognized the pure rMseno protein in both mice and piglets as evidenced by high levels of specific anti-rMseno antibodies, significantly increased levels of IFN-γ and IL-4 cytokines, and significantly increased T lymphocyte proliferation index. Piglets also had significantly increased levels of specific IgG₁, IgG_2a, CD4⁺, and CD8⁺ cells. The rMseno findings demonstrated a robust immunological response in mice and piglets, affording partial clinical protective efficacy in piglets.

Development of immunochromatographic strip assay for rapid detection of novel goose astrovirus

The novel goose astrovirus (GoAstV) is an emerging pathogenic virus that has resulted in large economic losses to the goose-rearing industry in China since 2016. The novel goose astrovirus cause gout in goslings with a mortality rate of around 50 %. Therefore, an effective diagnostic approach to monitor the spread of GoAstV is necessary. Here, a novel diagnostic immunochromatographic strip (ICS) assay was developed to detect GoAstV. A rapid immunochromatographic assay based on antibody colloidal gold nanoparticles specific to GoAstV was developed for the detection of GoAstV in goose allantoic fluid and supernatant of tissue homogenate. Monoclonal antibodies (Mabs) were prepared using the hybridoma technology, and the polyclonal antibodies (Pabs) were generated by immunizing the rabbits with recombinant ORF2 protein. In addition, the colloidal gold was prepared by reducing gold salt with sodium citrate coupled with Mabs against GoAstV. The optimal concentrations of the coating antibody and the capture antibody were examined as 1.6 mg/mL and 6 μg/mL. The optimal pH of the colloidal gold labeling was pH 8.0. With the visual observation, the lower limit of the ICS was reported to be approximately 1.2 μg/mL. Common diseases of goose were examined to assess the specificity of the ICS, and no cross-reaction was identified. 40 clinical positive samples were simultaneously detected by using the ICS and the PCR with a 92.5% coincidence rate between them. Furthermore, the mentioned samples could be stored at 25 °C and 4 °C for 4 and 6 months, respectively. It was proved that the ICS in this study was highly specific, sensitive, repeatable and more convenient to rapidly detect GoAstV in clinical samples.

Nanomaterials and nanocomposite applications in veterinary medicine

Nowadays, nanotechnology has made huge, significant advancements in biotechnology and biomedicine related to human and animal science, including increasing health safety, production, and the elevation of national income. There are various fields of nanomaterial applications in veterinary medicine such as efficient diagnostic and therapeutic tools, drug delivery, animal nutrition, breeding and reproduction, and valuable additives. Additional benefits include the detection of pathogens, protein, biological molecules, antimicrobial agents, feeding additives, nutrient delivery, and reproductive aids. There are many nanomaterials and nanocomposites that can be used in nanomedicine such as metal nanoparticles, liposomes, carbon nanotubes, and quantum dots. In the near future, nanotechnology research will have the ability to produce novel tools for improving animal health and production. Therefore, this chapter was undertaken to spotlight novel methods created by nanotechnology for application in the improvement of animal health and production. In addition, the toxicity of nanomaterials is fully discussed to avoid the suspected health hazards of toxicity for animal health safety.

Development of an Immunochromatographic Strip for Rapid Detection of Canine Adenovirus

Although canine adenovirus (CAdV) is highly prevalent in dogs, there is currently a lack of a quick diagnostic method. In this study, we developed a rapid immunochromatographic strip (ICS) assay using colloidal gold coupled to CAdV-2-specific monoclonal antibodies (mAbs). BALB/c mice were immunized with a purified CAdV-2 suspension, and four mAbs (belonging to two different epitopes) were generated and designated as 2C1, 7D7, 10D1, and 4G1. Western blot and protein spectral analysis indicated that the hexon protein of CAdV-2 recognized all four mAbs. The colloidal gold-coupled 7D7 and 2C1 mAbs were chosen for inclusion in the rapid ICS assay. The optimal concentrations of the coating antibody (2C1), the capture antibody (7D7), and the goat anti-mouse antibody were 1.0 mg/ml, 10 μg/ml, and 2.0 mg/ml, respectively. The limit of detection was approximately 2.0 × 10² tissue culture infective dose (TCID₅₀)/ml. Other common canine viruses were tested to evaluate the specificity of the ICS, and positive results were observed for only CAdV-1 and CAdV-2. The ICS test was conducted on 360 samples to detect CAdV, and the results were compared with those of polymerase chain reaction (PCR) tests. The ICS test was found to be a sufficiently sensitive and specific detection method for the convenient and rapid detection of CAdV.

Development of a Colloidal Gold Immunochromatographic Strip Assay for Rapid Detection of Bovine Rotavirus

Bovine rotavirus (BRV) is one of main pathogens responsible for diarrhea, fever, and vomiting. In this study, we developed a colloidal gold immunochromatographic test strip for detecting BRV according to the principle of double-antibody sandwich. The monoclonal antibodies (mAbs) and polyclonal antibodies (pAbs) were prepared and purified. On the strip, the purified mAbs labeled with the colloidal gold were used as the detector, and the goat anti-mouse antibodies and purified pAbs were coated on the nitrocellulose membranes as the control line and the test line, respectively. We optimized different reaction conditions, including the amount of mAbs, the pH of colloidal gold solution, coating solution, blocking solution, sample pad treatment solution, antibody concentration in control line, and antibody concentration in detection line. In specificity assay, the strip had high specificity in detecting BRV. No cross-reaction was observed in detecting other viruses. The detection sensitivity of the strip was found to be 1 × 10³ TCID₅₀/0.1 mL. Two hundred twenty clinical samples were detected with the strip compared to reverse transcription-polymerase chain reaction. No false-negative or false-positive results were found, and the results obtained by the two methods were similar. In conclusion, we developed a novel immunochromatographic strip to rapidly detect BRV. The strip developed exhibited high sensitivity and specificity for BRV detection. It could be a rapid, convenient, and effective method for the rapid diagnosis of BRV infection in the fields.

Serological and molecular rapid diagnostic tests for Toxoplasma infection in humans and animals

Infection by Toxoplasma gondii is prevalent worldwide. The parasite can infect a broad spectrum of vertebrate hosts, but infection of fetuses and immunocompromised patients is of particular concern. Easy-to-perform, robust, and highly sensitive and specific methods to detect Toxoplasma infection are important for the treatment and management of patients. Rapid diagnostic methods that do not sacrifice the accuracy of the assay and give reproducible results in a short time are highly desirable. In this context, rapid diagnostic tests (RDTs), especially with point-of-care (POC) features, are promising diagnostic methods in clinical microbiology laboratories, especially in areas with minimal laboratory facilities. More advanced methods using microfluidics and sensor technology will be the future trend. In this review, we discuss serological and molecular-based rapid diagnostic tests for detecting Toxoplasma infection in humans as well as animals.

Theranostics Aspects of Various Nanoparticles in Veterinary Medicine

Nanoscience and nanotechnology shows immense interest in various areas of research and applications, including biotechnology, biomedical sciences, nanomedicine, and veterinary medicine. Studies and application of nanotechnology was explored very extensively in the human medical field and also studies undertaken in rodents extensively, still either studies or applications in veterinary medicine is not up to the level when compared to applications to human beings. The application in veterinary medicine and animal production is still relatively innovative. Recently, in the era of health care technologies, Veterinary Medicine also entered into a new phase and incredible transformations. Nanotechnology has tremendous and potential influence not only the way we live, but also on the way that we practice veterinary medicine and increase the safety of domestic animals, production, and income to the farmers through use of nanomaterials. The current status and advancements of nanotechnology is being used to enhance the animal growth promotion, and production. To achieve these, nanoparticles are used as alternative antimicrobial agents to overcome the usage alarming rate of antibiotics, detection of pathogenic bacteria, and also nanoparticles being used as drug delivery agents as new drug and vaccine candidates with improved characteristics and performance, diagnostic, therapeutic, feed additive, nutrient delivery, biocidal agents, reproductive aids, and finally to increase the quality of food using various kinds of functionalized nanoparticles, such as liposomes, polymeric nanoparticles, dendrimers, micellar nanoparticles, and metal nanoparticles. It seems that nanotechnology is ideal for veterinary applications in terms of cost and the availability of resources. The main focus of this review is describes some of the important current and future principal aspects of involvement of nanotechnology in Veterinary Medicine. However, we are not intended to cover the entire scenario of Veterinary Medicine, despite this review is to provide a glimpse at potential important targets of nanotechnology in the field of Veterinary Medicine. Considering the strong potential of the interaction between the nanotechnology and Veterinary Medicine, the aim of this review is to provide a concise description of the advances of nanotechnology in Veterinary Medicine, in terms of their potential application of various kinds of nanoparticles, secondly we discussed role of nanomaterials in animal health and production, and finally we discussed conclusion and future perspectives of nanotechnology in veterinary medicine.

A Novel Diagnostic Method to Detect Duck Tembusu Virus: A Colloidal Gold-Based Immunochromatographic Assay

Duck Tembusu virus (DTMUV) is an emerging pathogenic flavivirus that has resulted in large economic losses to the duck-rearing industry in China since 2010. Therefore, an effective diagnostic approach to monitor the spread of DTMUV is necessary. Here, a novel diagnostic immunochromatographic strip (ICS) assay was developed to detect DTMUV. The assay was carried out using colloidal gold coated with purified monoclonal antibody A12D3 against envelope E protein. Purified polyclonal C12D1 antibodies from BALB/c mice against the envelope E protein were used as the capture antibody. Goat anti-mouse IgG was used to detect DTMUV, which was also assembled on the ICS. Results showed that the ICS could specifically detect DTMUV within 10 min. It also could be stored 25 and 4°C for 4 and 6 months, respectively. The sensitivity of the ICS indicated that the dilution multiples of positive allantoic fluid of DTMUV (LD50: 10^4.33/0.2 ml) was up to 200. Its specificity and sensibility showed no significant change under the above storage situations. Fifty clinical samples were simultaneously detected by ICS and reverse-transcription polymerase chain reaction with a 93.9% coincidence rate between them. It proved that the ICS in the present study was highly specific, sensitive, repeatable, and more convenient to rapidly detect DTMUV in clinical samples.

Development of Colloidal Gold-Based Immunochromatographic Assay for Rapid Detection of Goose Parvovirus

Goose parvovirus (GPV) remains as a worldwide problem in goose industry. For this reason, it is necessary to develop a new diagnostic approach that is easier and faster than conventional tests. A rapid immunochromatographic assay based on antibody colloidal gold nanoparticles specific to GPV was developed for the detection of GPV in goose allantoic fluid and supernatant of tissue homogenate. The monoclonal antibodies (Mab) was produced by immunizing the BALB/c mice with purified GPV suspension, and the polyclonal antibody (pAb) was produced by immunizing the rabbits with recombinant VP3 protein. The colloidal gold was prepared by the reduction of gold salt with sodium citrate coupled with Mab against GPV. The optimal concentrations of the coating antibody and capture antibody were determined to be 1.6 mg/ml and 9 μg/ml. With visual observation, the lower limit was found to be around 1.2 μg/ml. Common diseases of goose were tested to evaluate the specificity of the immune colloidal gold (ICG) strip, and no cross-reaction was observed. The clinical detection was examined by carrying out the ICG strip test with 92 samples and comparing the results of these tests with those obtained via agar diffusion test and polymerase chain reaction (PCR) test. Therefore, the ICG strip test was a sufficiently sensitive and accurate detection method for a rapid screening of GPV.

Prevalence and characterization of Panton-Valentine leukocidin-positive Staphylococcus aureus in bovine milk in Jabalpur district of Madhya Pradesh, India

Aim:

The study aimed to investigate the Panton-Valentine leukocidin (PVL)-positive Staphylococcus aureus in bovine milk due to its public health significance.

Materials and Methods:

A total of 400 milk samples of bovines taken from different dairy farms and outlets of Jabalpur were screened for the S. aureus and methicillin-resistant S. aureus (MRSA). The strains were tested for the PVL gene and antimicrobial sensitivity toward 10 different classes of antimicrobial agents. The PVL-positive S. aureus strains were further characterized by staphylococcal protein A or spa typing.

Result:

The prevalence of PVL-positive S. aureus was 10.53%. All the isolates positive for the PVL were resistant to methicillin, while the methicillin-sensitive S. aureus isolates were negative for the PVL. Five different spa types were found.

Conclusion:

The presence of PVL-positive MRSA in bovine milk close to consumer poses a potential public health risk to the community.

Development of an immunochromatographic assay as a screen for detection of total phthalate acid esters in cooking oil

Phthalate acid esters (PAEs) contamination raised concerns as a result of migration from food packaging and environmental exposure. Because of the adverse effects of PAE reported in humans, the aim of this study was to examine the ability to screen for the detection these chemicals as an indicator of potential exposure. Too develop a sensitive screening test to determine PAE, a specific polyclonal antibody against phthalic acid (PA), the hydrolysate of PAEs, was used as a marker of total PAEs. This method involved the use of 4-aminophthalic acid (APA) as an immunizing hapten to generate antibody. Subsequently, this antibody conjugated with labeled gold nanoparticles (GNPs) was then used to develop an immunochromatographic assay (ICA) for visually detecting PA. After establishing optimal assay conditions, the ICA strip detected visually PA at 3 μg/ml rapidly in less than 5 min. Further, this assay exhibited reliable specificity for PA with no apparent cross-reactivity with structurally related PAEs. A significant correlation between data obtained with the ICA strip and high-performance liquid chromatography (HPLC) analysis was achieved using cooking oils as model spiked samples. The proposed use of ICA offers an effective tool for rapid on-site screening for total PAEs in cooking oils.

Preparation of immunochromatographic strips for rapid detection of early secreted protein ESAT-6 and culture filtrate protein CFP-10 from Mycobacterium tuberculosis

The early secreted protein early secretory antigenic target 6(ESAT-6) and the culture filtrate protein 10 (CFP-10) are 2 antigens that are specific to Mycobacterium tuberculosis. These 2 antigens are good targets for tuberculosis (TB) detection.To rapidly diagnose TB across a variety of samples, we developed colloidal gold immunochromatographic strips (ICSs) based on ESAT-6 and CFP-10.The strips were evaluated using 233 samples, including sputum, plasma, and pleural effusion samples.The positive detection rates for ICSs for ESAT-6 and CFP-10 in sputum (culture-positive for M tuberculosis) were 100% and 91.2%, respectively. The positive detection rates for ICSs for ESAT-6 and CFP-10 in plasma were 34.1% and 29.4%, respectively. The positive detection rates for ICSs for ESAT-6 and CFP-10 in pleural effusion were 64.7% and 55.9%, respectively. Experimental analysis of culture supernatant showing that the ICS developed for ESAT-6 had a sensitivity of 100% and a specificity of 91.2%. While the ICS developed for CFP-10 had a sensitivity of 91.2% and a specificity of 88.2%.The validity of the test is limited by source of sample. The technique is sensitive and specific for samples in sputum and culture media but not for plasma or pleural effusion samples. Detection of M tuberculosis using ICSs is rapid, simple, and relatively effective; thus, ICSs are a potential screening tool for TB.

A sensitive and rapid immunoassay for Mycoplasma pneumoniae in children with pneumonia based on single-walled carbon nanotubes

Mycoplasma pneumoniae(MP) is a leading pathogen of respiratory infection, especially community-acquired pneumonia (CAP), in children worldwide. However, its diagnosis is frequently ineffective because bacterial culture and serology test are usually positive 1–2 weeks or more after the disease onset. To achieve a better detection efficiency, the single-walled carbon nanotubes(SWCNT) were coupled with the colloidal gold-monoclonal antibody immunochromatographic strips(CGIC). Interestingly, the SWCNT/CGIC assay allowed MP identification, with a detection limit of 1 × 10² copies/ml. Using referenced throat swabs of 97 MP and 40 non-MP cases, the assay yielded 72.2% sensitivity, 100.0% specificity, 100.0% positive predictive value (PPV), 59.7% negative predictive value (NPV). In summary, our assay was far more effective than any conventional methods for the diagnosis of acute MP. The ease of use, rapid and stability further enhance its feasibility for clinical use on-site.

A novel colloidal gold immunochromatography assay strip for the diagnosis of schistosomiasis japonica in domestic animals

Background

Schistosomiasis remains a major public health concern in China and an epidemiological survey has revealed that schistosome-infected bovines and goats are the main transmission sources for the disease. Therefore, development of a sensitive technique for the diagnosis of schistosomiasis in domestic animals is necessary.

Method

A novel colloidal gold immunochromatography assay (GICA) strip was developed for detecting Schistosoma japonicum in domestic animals. The colloidal gold was conjugated with recombinant streptococcal protein G (rSPG). As the test and control lines, the schistosome soluble egg antigen and rSPG, respectively, were blotted on nitrocellulose membrane.

Results

The lowest detectable serum dilution was 1∶640 for schistosome-infected buffaloes. The cross-reaction rate of GICA was 14.29% with Paramphistomum sp. in buffaloes, 16.67% with Haemonchus sp. in goats, and 33.33% with Orientobilharzia sp. in goats. These results were slightly lower and similar to those obtained through ELISA. Moreover, the strips for detecting S. japonicum in mice, rabbits, buffaloes, and goats showed high sensitivity (100.00%, 100.00%, 100.00%, and 100.00%, respectively) and specificity (100.00%, 100.00%, 94.23%, and 88.64%, respectively). And the sensitivity or specificity of the GICA strips did not present any significant differences after storage for 12 months at room temperature. When compared with ELISA, the GICA strips exhibited similar sensitivity and specificity in the diagnosis of schistosomiasis in mice, rabbits, buffaloes, and goats. Besides, only 5 μl of serum are required for the test and the detection can be completed within 5 min.

Conclusion

This study is the first to develop a GICA strip using gold–rSPG conjugate for the diagnosing of schistosomiasis in domestic animals, and preliminary results showed that the developed strip may be suitable for large-scale screening of schistosomiasis in endemic areas.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0297-z) contains supplementary material, which is available to authorized users.

Development of a colloidal gold immunochromatographic strip for rapid detection of Streptococcus agalactiae in tilapia

A colloidal gold immunochromatographic strip was developed for rapid detection of Streptococcus agalactiae (S. agalactiae) infection in tilapia. The monoclonal antibodies (mAb) 4C12 and 3A9 were used to target S. agalactiae as colloidal gold-mAb conjugate and captured antibody, respectively. The colloidal gold immunochromatographic strip was assembled via routine procedures. Optimal pH and minimum antibody levels in the reaction system for gold colloidal-mAb 4C12 conjugation were pH 7.4 and 18μg/mL, respectively. Optimal concentrations of the captured antibody 3A9 and goat anti-mouse antibody were 0.6mg/mL and 2mg/mL, respectively. The sensitivity of the strip for detecting S. agalactiae was 1.5×10⁵ colony forming units (CFU). No cross-reaction was observed with other commonly encountered bacteria, including Pseudomonas fluorescens, Aeromonas hydrophila, Vibrio anguillarum and Streptococcus iniae. The assay time for S. agalactiae was less than 15min. Tilapia samples artificially infected with S. agalactiae were tested using the newly developed strip. The results indicated that blood, brain, kidney, spleen, metanephros and intestine specimens of infected fish can be used for S. agalactiae detection. The validity of the strip was maintained for 6 months at 4°C. These findings suggested that the immunochromatographic strip was effective for spot and rapid detection of S. agalactiae infected tilapia.

Recent Progresses in Nanobiosensing for Food Safety Analysis

With increasing adulteration, food safety analysis has become an important research field. Nanomaterials-based biosensing holds great potential in designing highly sensitive and selective detection strategies necessary for food safety analysis. This review summarizes various function types of nanomaterials, the methods of functionalization of nanomaterials, and recent (2014-present) progress in the design and development of nanobiosensing for the detection of food contaminants including pathogens, toxins, pesticides, antibiotics, metal contaminants, and other analytes, which are sub-classified according to various recognition methods of each analyte. The existing shortcomings and future perspectives of the rapidly growing field of nanobiosensing addressing food safety issues are also discussed briefly.

Development of a Calibration Strip for Immunochromatographic Assay Detection Systems

With many benefits and applications, immunochromatographic (ICG) assay detection systems have been reported on a great deal. However, the existing research mainly focuses on increasing the dynamic detection range or application fields. Calibration of the detection system, which has a great influence on the detection accuracy, has not been addressed properly. In this context, this work develops a calibration strip for ICG assay photoelectric detection systems. An image of the test strip is captured by an image acquisition device, followed by performing a fuzzy c-means (FCM) clustering algorithm and maximin-distance algorithm for image segmentation. Additionally, experiments are conducted to find the best characteristic quantity. By analyzing the linear coefficient, an average value of hue (H) at 14 min is chosen as the characteristic quantity and the empirical formula between H and optical density (OD) value is established. Therefore, H, saturation (S), and value (V) are calculated by a number of selected OD values. Then, H, S, and V values are transferred to the RGB color space and a high-resolution printer is used to print the strip images on cellulose nitrate membranes. Finally, verification of the printed calibration strips is conducted by analyzing the linear correlation between OD and the spectral reflectance, which shows a good linear correlation (R² = 98.78%).

Multi-residue fluorescent microspheres immunochromatographic assay for simultaneous determination of macrolides in raw milk

A rapid, reliable, sensitive, and quantitative multi-residue fluorescent microspheres immunochromatographic assay (FMCA) was developed for simultaneous detection of four macrolides in raw milk. The IC50 value of the optimized FMCA was 1.36, 1.22, 1.01, and 1.39 ng/mL for erythromycin (ERY), spiramycin (SPI), tilmicosin (TIM), and tylosin (TYL), respectively. The limits of detection (LODs) for the four macrolides was 0.13 ng/mL. The recoveries of ERY, SPI, TIM, and TYL from spiked raw milk ranged from 91.8-109.2, 89.6-114.4, 84.8-111.6, and 85.8-115.2%, respectively, with coefficients of variation (CVs) of 5.4-11.3, 7.9-15.7, 6.2-13.7, and 3.2-14.9%, respectively. The whole testing process was completed within 20 min. The antibody-mixed labeled method was successfully applied to the FMCA, which greatly simplified the operation steps and saved a lot of time. Compared with the immunogold chromatographic assay (IGCA), the FMCA is more sensitive and stable and has less antibody consumption. A parallel analysis in blind raw milk samples was conducted by liquid chromatography-tandem mass spectrometry (LC-MS/MS); the results showed good correlation (r(2) = 0.99) between the two methods. Therefore, the developed multi-residue FMCA is reliable and can be easily applied to other antibiotics or other contaminants.

A novel diagnostic approach to detecting porcine epidemic diarrhea virus: The lateral immunochromatography assay

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A novel lateral immunochromatography (IC) assay was developed to detect PEDV antigen.

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The IC assay has 96.0% sensitivity and 98.5% specificity compared with real-time reverse transcriptase PCR.

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The detection limit for PEDV was 1 × 10³ copies.

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The IC assay could be stored at 4 °C or room temperature for 15 months without affecting its efficacy.

Porcine epidemic diarrhea virus (PEDV) causes acute diarrhea and dehydration in sucking piglets and has a high mortality rate. An immunochromatography (IC) assay, known as a lateral flow test, is a simple device intended to detect the presence of target pathogens. Here, we developed an IC assay that detected PEDV antigens with 96.0% (218/227) sensitivity and 98.5% (262/266) specificity when compared with real-time reverse transcriptase (RT)-PCR using FAM-labeled probes based on sequences from nucleocapsid genes. The detection limits of the real-time RT-PCR and IC assays were 1 × 10² and 1 × 10³ copies, respectively. The IC assay developed herein did not detect non-specific reactions with other viral or bacterial pathogens, and the assay could be stored at 4 °C or room temperature for 15 months without affecting its efficacy. Thus, the IC assay may result in improved PED detection and control on farms, and is a viable alternative to current diagnostic tools for PEDV.

Establishment of Magnetic Microparticles-Assisted Time-Resolved Fluoroimmunoassay for Determinating Biomarker Models in Human Serum

In order to early screen and detect suspected biomarkers from pathogens and the human body itself, tracers or reaction strategies that can act as signal enhancers have been proposed forth at purpose. In this paper, we discussed the applicability of magnetic microparticles-assisted time-resolved fluoroimmunoassay (MMPs-TRFIA) for sensitive determination of potential analytes. Hepatitis B e antigen, antibody to hepatitis B surface antigen and free triiodothyronine were used as biomarker models to explore the reliability of the method. By coupling with bioprobes, MMPs were used as immunoassay carriers to capture target molecules. Under optimal condition, assay performance, including accuracy, precision and specificity, was outstanding and demonstrated satisfactory. To further evaluate the performance of the MMPs-TRFIA in patients, a total of 728 serum samples from hospital were analyzed for three biomarkers in parallel with the proposed method and chemiluminescence immunoassay kit commercially available. Fairly good agreements are obtained between the two methods via data analysis. Not only that but the reliability of MMPs-TRFIA has also been illustrated by three different reaction models. It is confirmed that the novel method modified with MMPs has been established and showed great potential applications in both biological detection and clinical diagnosis, including big molecule protein and low molecular weight haptens.

Development of a colloidal gold immunochromatographic strip for the rapid detection of soft-shelled turtle systemic septicemia spherical virus

A colloidal gold immunochromatographic strip (ICS) test based on a competitive format was developed for the rapid detection of soft-shelled turtle systemic septicemia spherical virus (STSSSV) in turtle and fecal samples. Specific egg yolk antibodies (IgY) against STSSSV were labeled with colloidal gold and used as probes in the one-step test strip. Antigen (STSSSV) and goat anti-chicken IgY were drawn on the nitrocellulose membrane as the test line and control line, respectively. When STSSSV standard samples (0-100μg/mL) were detected by the strips, the visual limit of detection (LOD) was found to be 50.0μg/mL. The ICS test showed high stability; the strips were stable for at least 3 months at 4°C without significant loss of activity. There was no obvious cross-reactivity with other aquatic pathogens. The assay can be performed within 5-10min. Analysis of STSSSV in turtle samples revealed that data obtained from the ICS test were in a good agreement with those obtained by ELISA. The positive results of fecal samples suggested that this method could be used to detect STSSSV while protecting the animals' welfare. The ICS assay does not need specialized equipment or a technician and can be used as a reliable, rapid, cost-effective and convenient qualitative tool for on-site diagnosis.

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.