On-site rapid detection of multiple pesticide residues in tea leaves by lateral flow immunoassay

The application of pesticides (mostly insecticides and fungicides) during the tea-planting process will undoubtedly increase the dietary risk associated with drinking tea. Thus, it is necessary to ascertain whether pesticide residues in tea products exceed the maximum residue limits. However, the complex matrices present in tea samples comprise a major challenge in the analytical detection of pesticide residues. In this study, nine types of lateral flow immunochromatographic strips (LFICSs) were developed to detect the pesticides of interest (fenpropathrin, chlorpyrifos, imidacloprid, thiamethoxam, acetamiprid, carbendazim, chlorothalonil, pyraclostrobin, and iprodione). To reduce the interference of tea substrates on the assay sensitivity, the pretreatment conditions for tea samples, including the extraction solvent, extraction time, and purification agent, were optimized for the simultaneous detection of these pesticides. The entire testing procedure (including pretreatment and detection) could be completed within 30 min. The detected results of authentic tea samples were confirmed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), which suggest that the LFICS coupled with sample rapid pretreatment can be used for on-site rapid screening of the target pesticide in tea products prior to their market release.

Establishment of Double-antigen Sandwich Time-resolved Fluorescence Immunoassay for Detection of Pest des Petits Ruminants Virus

[Objectives]This study was conducted to explore rapid and large-scale screening and detection of peste des petits ruminants(PPR),so as to provide important technical means for prevention,control and purification of PPR.[Methods]Soluble N protein and NH fusion protein were successfully obtained in an Escherichia coli expression system by optimizing E.coli codon and expression conditions.Furthermore,based on purified soluble N protein and NH fusion protein,a double-antigen sandwich time-resolved fluorescence immunoassay method for detection of peste des petits ruminants virus(PPRV)was established.[Results]The method has high sensitivity and specificity and can specifically detect the antibody against PPRV in sheep serum,and it has no cross reaction with other related diseases.The method was used to detect 292 clinical samples,and compared with French IDVET competition ELISA kit.The coincidence rates of positive samples and negative samples from the two kinds of test kits were 92.47%and 97.26%,respectively,and the overall coincidence rate was 94.86%.The intra-group and inter-group coefficients of variation in the repeatability test were less than 10%.[Conclusions]Compared with the traditional ELISA method,the double-antigen sandwich time-resolved fluorescence immunoassay for detection of PPRV has equivalent sensitivity and specificity,and simple and rapid operation,and thus high application and popularization value.

Harmonization of SARS-CoV-2 antigen immunoassays:are they measuring the same“thing”?

Background:This study was planned to assess the accuracy and comparability of two commercially available,laboratory-based SARS-CoV-2(severe acute respiratory syndrome)antigen(Ag)immunoassays.Methods:We studied a cohort of subjects with acute SARS-CoV-2 infection,from whom a nasopharyngeal swab was taken and tested with a molecular assay(Altona Diagnostics RealStar SARS-CoV-2 RT-PCR Kit)and two laboratory-based,fully automated SARS-CoV-2 Ag immunoassays(Fujirebio Lumipulse G SARS-CoV-2 Ag and Roche Elecsys SARS-CoV-2 Ag).Results:The final population consisted in 93 subjects testing positive for SARS-CoV-2 RNA,34 with cycle threshold(Ct)values<29.5.The results of the two SARS-CoV-2 Ag immunoassays were significantly intercorrelated(r=0.77;P<0.001)in the entire cohort,though such correlation considerably improved in patients with high viral load(cycle threshold values<29.5:r=0.96;P<0.001).The accuracy for identifying samples with high viral load was excellent for both Lumipulse G SARS-CoV-2 Ag(AUC,0.99;P<0.001)and Elecsys SARS-CoV-2 Ag(AUC,0.99;P<0.001),with best cut-offs of 2.03 ng/mL for Lumipulse G SARS-CoV-2 Ag(1.00 sensitivity and 0.88 specificity)and 0.70 COI for Elecsys SARS-CoV-2 Ag(1.00 sensitivity and 0.80 specificity),respectively.Conclusion:The results of this study provide valuable support to usability of fully-automated,rapid,high throughput and accurate SARS-CoV-2 Ag immunoassays for complementing molecular assays.

Determination of theophylline concentration in serum by chemiluminescent immunoassay

Objective: This study aimed to establish chemiluminescent immunoassay (CLIA) for quantitative determination of theophylline levels in human serum. Methods: To measure the concentration of theophylline (n=122) and evaluate the assay.Results: The linear range of the CLIA method was 0.51～40 mg/L (Y=1.02X+0.44, r=0.995). The intra and inter CV (coefficient variance) of CLIA were 3.20% and 3.57%, respectively. The average recovery rate was 102.3%. This method was free from interference by brilirubin (＜200 μmol/L), hemoglobin (＜10 g/L), and triglycerides (＜15 mmol/L). Conclusion: This method is simple, convenient and precise for clinical pharmacokinetics study oftheophylline.

The Development of A Fluorescence Polarization Immunoassay for Aflatoxin Detection

A fluorescence polarization immunoassay （FPIA） was developed for the analysis ofaflatoxins （AFs） using an anti-aflatoxin B1 （AFB1） monoclonal antibody and a novel fluorescein-labeled AFB1 tracer. The FPIA showed an IC50 value of 23.33 ng/mL with a limit of detection of 13.12 ng/mL for AFB1. The cross-reactivities of AFB1, AFB2, AFG1, AFG2, AFM1, and AFM2 with the antibody were 100%, 65.7%, 143%, 23.5%, 111.4%, and 2%, respectively. The group-specificity of anti-AFB1mAb indicated that the FPIA could potentially be used in a screening method for the detection of total AFs, albeit not AFG2 and AFM2. The total time required for analyzing 96 samples in one microplate was less than 5 rain. This study demonstrates the potential usefulness of the FPIA as a rapid and simple technique for monitoring AFs.

Detection of anti-preS1 antibodies for recovery of hepatitis B patients by immunoassay

AIM: To establish a convenient immunoassay method based on recombinant antigen preS1(21-119aa) to detect anti-preS1 antibodies and evaluate the clinical significance of antibodies in hepatitis B. METHODS: The expression plasmid pET-28a-preS1 was constructed, and a large quantity of preS1(21-119aa) fragment of the large HBsAg protein was obtained. The preS1 fragment purified by Ni(2+)-IDA affinity chromatography was used as coated antigen to establish the indirect ELISA based on streptavidin-biotin system for detection of the anti-preS1 antibodies in sera from HBV-infected patients. For follow-up study, serial sera were collected during the clinical course of 21 HBV-infected patients and anti-preS1 antibodies, preS1 antigen, HBV-DNA and other serological HBV markers were analyzed. RESULTS: preS1(21-119aa) fragment was highly expressed from the plasmid pET-28a-preS1 in a soluble form in E.Coli (30mg.L(-1)), and easily purified to high purity over 90% by one step of Ni(2+)-IDA-sepharose 6B affinity chromatography. The purity and antigenicity of the purified preS1(21-119aa) protein was determined by 150g.L(-1) SDS-PAGE, Western blot and a direct ELISA. Recombinant preS1(21-119aa) protein was successfully applied in the immunoassay which could sensitively detect the anti-preS1 antibodies in serum specimens of acute or chronic hepatitis B patients. Results showed that more than half of 19 acute hepatitis B patients produced anti-preS1 antibodies during recovery of the disease, however, the response was only found in a few of chronic patients. In the clinical follow-up study of 11 patients with anti-preS1 positive serological profile, HBsAg and HBV-DNA clearance occurred in 6 of 10 acute hepatitis B patients in 5-6 months, and seroconversion of HBeAg and disappearance of HBV-DNA occurred in 1 chronic patients treated with lavumidine, a antiviral agent. CONCLUSION: The high-purity preS1(21-119aa) coated antigen was successfully prepared by gene expression and affinity chromatography. Using this antigen, a conveniently detective system of anti-preS1 antibodies in sera was established. Preliminarily clinical trial the occurrence of anti-preS1 antibodies in acute hepatitis B patients suggests the clearance of HBV from serum in a short-term time, and anti-preS1 positive in chronic patients means health improvement or recovery from the disease.

Chemiluminescence enzyme immunoassay based on magnetic nanoparticles for detection of hepatocellular carcinoma marker glypican-3

Glypican-3 （GPC3） is reported as a great promising tumor marker for hepatocellular carcinoma （HCC） diagnosis. Highly sensitive and accurate analysis of serum GPC3 （sGPC3）, in combination with or instead of traditional HCC marker alpha-fetoprotein （AFP）, is essential for early diagnosis of I-ICC. Biomaterial-functionalized magnetic particles have been utilized as solid supports with good biological compatibility for sensitive immunoassay. Here, the magnetic nanoparticles （MnPs） and magnetic microparticles （MmPs） with carboxyl groups were further modified with streptavidin, and applied for the development of chemiluminescence enzyme immunoassay （CLEIA）. After comparing between MnPs- and MmPs-based CLEIA, MnPs-based CLEIA was proved to be a better method with less assay time, greater sensitivity, better linearity and longer chemiluminescence platform. MnPs-based CLEIA was applied for detection of sGPC3 in normal liver, hepatocirrhosis, secondary liver cancer and HCC serum samples. The results indicated that sGPC3 was effective in diagnosis of HCC with high performance.

Hierarchical Nanogold Labels to Improve the Sensitivity of Lateral Flow Immunoassay

Lateral flow immunoassay(LFIA) is a widely used express method and offers advantages such as a short analysis time, simplicity of testing and result evaluation.However, an LFIA based on gold nanospheres lacks the desired sensitivity, thereby limiting its wide applications.In this study, spherical nanogold labels along with new types of nanogold labels such as gold nanopopcorns and nanostars were prepared, characterized, and applied for LFIA of model protein antigen procalcitonin. It was found that the label with a structure close to spherical provided more uniform distribution of specific antibodies on its surface, indicative of its suitability for this type of analysis.LFIA using gold nanopopcorns as a label allowed procalcitonin detection over a linear range of 0.5–10 ng mL^(-1) with the limit of detection of 0.1 ng mL^(-1), which was fivefold higher than the sensitivity of the assay with gold nanospheres. Another approach to improve the sensitivity of the assay included the silver enhancement method,which was used to compare the amplification of LFIA for procalcitonin detection. The sensitivity of procalcitonin determination by this method was 10 times better the sensitivity of the conventional LFIA with gold nanosphere as a label. The proposed approach of LFIA based on gold nanopopcorns improved the detection sensitivity without additional steps and prevented the increased consumption of specific reagents(antibodies).

Comparison of chemiluminescence enzyme immunoassay based on magnetic microparticles with traditional colorimetric ELISA for the detection of serum α-fetoprotein

A chemiluminescence enzyme immunoassay based on magnetic microparticles (MmPs-CLEIA) was developed to evaluate serum a-fetoprotein (AFP) in parallel with traditional colorimetric enzyme-linked immunosorbent assay (ELISA).A systematic comparison between the MmPs-CLEIA and colorimetric ELISA concluded that the MPs-CLEIA exhibited fewer dosages of immunoreagents,less total assay time,and better linearity,recovery,precision,sensitivity and validity.AFP was detected in forty human serum samples by the proposed MPs-CLEIA and ELISA,and the results were compared with commercial electrochemiluminescence immunoassay (ECLIA) kit.The correlation coefficient between MPs-CLEIA and ELISA was obtained with R 2 0.6703;however,the correlation between MPs-CLEIA and ECLIA (R 2 0.9582) was obviously better than that between colorimetric ELISA and ECLIA (R 2 0.6866).

Immunoassay of chemical contaminants in milk:A review

The detection of chemical contaminants is critical to ensure dairy safety. These contaminants include veterinary medicines, antibiotics, pesticides, heavy metals, mycotoxins, and persistent organic pollutants （POPs）. Immunoassays have recently been used to detect contaminants in milk because of their simple operation, high speed, and low cost. This article describes the latest developments in the most important component of immunoassays--antibodies, and then reviews the four major substrates used for immunoassays （i.e., microplates, membranes, gels, and chips） as well as their use in the detection of milk contaminants. The paper concludes with prospects for further aDDlications of these immunoassavs.

A New Hapten for Immunoassay of Aldicarb

A new hapten, aldicarb oxime succinic ester （AOSE）, was synthesized for immunoassay of aldicarb. It was conjugated to proteins by active ester method. Polyclonal antibody was raised against AOSE-BSA （bovine serum albumin） conjugate. Enzyme-linked immunosorbent assays （ELISAs） showed that this antiserum had high affinity to aldicarb and can be used for sensitive and selective immunoassay of aldicarb.

Characterization of Hapten-Protein Conjugates for Immunoassay of Polycyclic Aromatic Hydrocarbons(PAHs)

Preparation and characterization of the hapten-protein conjugates are fundamental to developing environmental immunoassays. As a hapten, 1-pyrenebutyric acid（PBA） was conjugated to the carrier protein of bovine serum albumin（BSA） or ovalbumin（OVA） by active ester method. Infrared spectra（IR） showed that PBA-BSA and PBA-OVA conjugates were successfully prepared. The number of the haptens conjugated to the carrier protein was determined by ultraviolet spectra（UV） and matrix-assisted laser desorption ionization time-of-flight mass spectrometry（MALDI-TOF-MS）. The calculated average binding ratios of PBA/BSA and PBA/OVA were 18：1 and 10：1 by UV, and 31：1 and 22：1 by MALDI-TOF-MS, respectively. Although there was a discrepancy between the results determined by the two methods, both of them were useful for the characterization of the hapten-protein conjugates. The antibody was produced against the antigen of PBA-BSA, and the affinity was tested by the double agar diffusion method The conjugates and the antibody could be used for developing a sensitive and selective immunoassay of polycyclic aromatic hydrocarbons（PAHs）.

Lateral Flow Immunoassay for Quantitative Detection of Ractopamine in Swine Urine

A strip reader based lateral flow immunoassay （LFIA） was established for the rapid and quantitative detection of ractopamine （RAC） in swine urine. The ratio of the optical densities （ODs） of the test line （AT） to that of the control line （Ac） was used to effectively minimize interference among strips and sample variations. The linear range for the quantitative detection of RAC was 0.2 ng/mL to 3.5 ng/mL with a median inhibitory concentration （IC50） of 0.59＋0.06 ng/mL. The limit of detection （LOD） of the LFIA was 0.13 ng/mL. The intra-assay recovery rates were 92.97%, 97.25%, and 107.41%, whereas the inter-assay rates were 80.07%, 108.17%, and 93.7%, respectively.

Rapid and Sensitive Chemiluminescent Enzyme Immunoassay for the Determination of Neomycin Residues in Milk

Immunoassays greatly contribute to veterinary drug residue analysis. However, there are few reports on detecting neomycin residues by immunoassay. Here, a rapid and sensitive chemiluminescent enzyme immunoassay （CLIEA） was successfully developed for neomycin residue analysis. CLIEA demonstrated good cross-reactivity for neomycin, and the IC50 value was 2.4 ng/mL in buffer.

Development of Lateral-flow Immunoassay for WSSV with Polyclonal Antibodies Raised against Recombinant VP (19+28) Fusion Protein

我们为 WSSV 开发了敏感、快速的侧面流动的免疫分析(LFIA ) ，用象指示物的胶体的黄金。熔化蛋白质， VP (19+28 ) ，在 E 被表示。coli，净化并且过去常准备 polyclonal 抗体。净化的 anti-VP (19+28 ) IgG 与胶体的黄金被结合。Unconjugated anti-VP (19+28 ) IgG 和山羊反兔子 IgG 在硝化纤维素膜上被使不能调动。在汇编以后，虾样品的三个组(在每个组的 5 个单个动物) 被测试它包括了健康、垂死、死了的虾。为每个组，三不同纸巾(身体蜜汁，鳃和 hepatopancreas ) 同时被测试。在平行，所有样品也为比较用 PCR 被分析。从测试的 45 件样品，当 15 作为否定被分类时， 30 作为积极被检测。LFIA 的结果相关，那些由 PCR 分析获得了，显示这二个察觉方法有在在这初步的研究测试的样品的有限数字的一样的功效。关键词侧面流动的免疫分析 - 白点症候群病毒(WSSV )- VP19 - VP28 CLC 数字 S945.

The clinical value of enzyme-multiplied immunoassay technique monitoring the plasma concentrations of cyclosporine A after renal transplantation

The feasibility and the clinical value of the enzyme-multiplied immunoassay technique （EMIT） monitoring of blood concentrations of cyclosporine A （CsA） in patients treated with CsA were investigated after kidney transplantation. The validation method was performed to the EMIT determination of CsA blood concentration, the CsA whole blood trough concentrations （Co） of patients in different time periods after renal transplantation were monitored, and combined with the clinical complications, the statistical results were analyzed and compared. EMIT was precise, accurate and stable, also with a high quality control. The mean postoperative blood concentration of CsA was as follows： 〈1 month, （281.4± 57.9）ng/mL; 2 - 3 months, （264.5 ± 41.2） ng/mL; 4 - 5 months, （236.4 ± 38.9） ng/mL; 6 - 12 months, （206.5± 32.6）ng/mL; 〉12 months, （185.6± 28.1）ng/mL. The toxic reaction rate of CsA blood concentration within the recommended therapeutic concentration was 14.1%, significantly lower than that of the none-recommended dose group （37.2%） （P〈0.05）; the transplantation rejection rate was 4.4%, significantly lower than that of the none- recommended dose group （22.5%） （P〈0.05）. Using EMIT to monitor the blood concentration of CsA as the routine laboratory method is feasible, and is able to reduce the CsA toxicity and rejection significantly, leading to achieving the desired therapeutic effect.

Quantum Dot Nanobeads-Labelled Lateral Flow Immunoassay Strip for Rapid and Sensitive Detection of Salmonella Typhimurium Based on Strand Displacement Loop-Mediated Isothermal Amplification

Rapid,sensitive,point-of-care detection of pathogenic bacteria is important for food safety.In this study,we developed a novel quantum dot nanobeads-labelled lateral flow immunoassay strip(QBs-labelled LFIAS)combined with strand displacement loop-mediated isothermal amplification(SD-LAMP)for quantitative Salmonella Typhimurium(ST)detection.Quantum dot nanobeads(QBs)served as fluorescence reporters,providing good detection efficiency.The customizable strand displacement(SD)probe was used in LAMP to improve the specificity of the method and prevent by-product capture.Detection was based on a sandwich immunoassay.A fluorescence strip reader measured the fluorescence intensity(FI)of the test(T)line and control(C)line.The linear detection range of the strip was 10^(2)–10^(8) colony forming units(CFU)·mL^(-1).The visual limit of detection was 10^(3) CFU·mL^(-1),indicating that the system was ten-fold more sensitive than AuNPs-labelled test strips.ST specificity was analyzed in accordance with agarose gel outputs of polymerase chain reaction(PCR)and SD-LAMP.We detected ST in foods with an acceptable recovery of 85%–110%.The method is rapid,simple,almost equipment-free,and suitable for bacterial detection in foods and for clinical diagnosis.

Recent advances in immunoassays and biosensors for mycotoxins detection in feedstuffs and foods

Mycotoxins are secondary metabolites produced by fungus.Many mycotoxin species are highly toxic and are frequently found in cereals and feedstuffs.So,powerful detection methods are vital and effective ways to prevent feed contamination.Traditional detection methods can no longer meet the needs of massive,real-time,simple,and fast mycotoxin monitoring.Rapid detection methods based on advanced material and sensor technology are the future trend.In this review,we highlight recent progress of mycotoxin rapid detection strategies in feedstuffs and foods,especially for simultaneous multiplex mycotoxin determination.Immunoassays,biosensors,and the prominent roles of nanomaterials are introduced.The principles of different types of recognition and signal transduction are explained,and the merits and pitfalls of these methods are compared.Furthermore,limitations and challenges of existing rapid sensing strategies and perspectives of future research are discussed.

Capillary Electrophoretic Immunoassay with Laser-induced Fluorescence Detection for Interferon-gamma

Capillary electrophoretic immunoassay with laser-induced fluorescence detection for recombinant human interferon-gamma (IFN-g) was established. The limits of detection for three forms of IFN-g are 6.9 ng/L, 5.7 ng/L and 5.0 ng/L, respectively.

Electrochemiluminescence immunoassay method underestimates cortisol suppression in ulcerative colitis patients treated with oral prednisone

AIM: To evaluate cortisolemia by using conventional electrochemiluminescence immunoassay (ECLIA) method compared to liquid chromatography-tandem mass spectrometry (LC-MS/MS) method in active ulcerative colitis (UC) patients treated with oral prednisone (PD).