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Introduction Plants containing aristolochic acid and its derivatives are nephrotoxic, mutagenic, and carcinogenic to humans; chronic diet poisoning caused by the aristolochic acid is the cause of endemic (Balkan) nephropathy and related cancers. Objective To develop a colloidal gold immunochromatographic test strip (ICS) based on the competitive format for the rapid detection of aristolochic acid A (AA-A) in herbal medicinal materials. Materials and methods For the ICS based on gold nanoparticles (AuNPs), the antigen [AA-A-bovine serum albumin (BSA)], and goat anti-mouse IgG were drawn on the nitrocellulose membrane as the test line (T line) and the control line (C line), respectively. Monoclonal antibody (MAb)-AuNP conjugates were sprayed onto the conjugate pad. The sensitivity of the ICS was 6 ng/mL, and the test was completed in 10 min. The analysis of AA-A in traditional Chinese medicine samples showed that the ICS results were in good agreement with those obtained by high-performance liquid chromatography methods. Conclusion These results demonstrated that the ICS test could be used as a reliable, rapid, cost-effective, and convenient qualitative tool for on-site screening techniques to detect AA-A in herbal medicinal materials without any special instrumentation.

For the rapid control of the highly toxic phycotoxin microcystin-LR in seafood, immunochromatographic test systems have been developed and compared using two types of gold nanoparticles as markers, namely, spherical particles and nanoflowers. The test systems are based on an indirect competitive assay, in which the detectable immune complexes include native microcystin-LR-specific antibodies and nanoparticle-labeled anti-species antibodies. The developed test systems allow for the detection of microcystin-LR within 18 min with instrumental detection limits of 0.2 and 0.1 ng/mL when using spherical nanoparticles and gold nanoflowers, respectively. The visual detection limit is 1 ng/mL for both formats. The parameters of nanoparticles, which determine the analytical characteristics of the corresponding test systems are characterized. The applicability of the developed test systems for the control of contamination of fish and seafood (shrimp, octopus, squid, and mussels) combining rapid stages of sample preparation and immunochromatography has been shown.

In this work, we synthesized a novel hyperbranched Au plasmonic blackbody (AuPB) and applied it as a signal amplification label in immunochromatographic test strip (ICTS) sensor for the sensitive detection of aflatoxin B1 (AFB1) in maize. AuPB were characterized with high color signal intensity, superior colloidal stability, and excellent biocompatibility benefiting from the hyperbranched structure and the dense polydopamine layer on surface, which contributes to improving the sensitivity and robustness of competitive ICTS sensor. Under the optimized conditions, the half inhibition concentration and the detection limit of our AuPB-enhanced ICTS (AuPB-ICTS) sensor were 0.087 and 0.016 ng/mL, which are 3.9- and 5.4-fold lower than those of traditional ICTS sensor based on 35-nm gold nanospheres as signal reporters. The average recoveries for the intra- and inter-assay ranged from 92.5 to 119.5%, with the coefficient of variation of 3.29–10.28%. Moreover, the reliability and practicability of this method were validated by the well-established ultra-performance liquid chromatography method via simultaneously measuring fifteen naturally contaminated maize samples. In summary, the developed AuPB-ICTS sensor can serve as an alternative rapid diagnostic method to allow the sensitive and reliable screening of AFB1 in maize.

Based on the successful derivation of a hapten, we prepared and optimized a murine monoclonal antibody against imidocarb, with an IC50 of 2.22 ng/mL and a limit of detection (LOD) of 0.45 ng/mL. Cross-experiment results showed that the cross-over rate for 4,4'-dinitrocarbanilide was 18.12%, and the cross-reactivity with other analogues when using the ic ELISA was less than 0.1%. We used the developed ic-ELISA to detect the addition and recovery of imidocarb in milk and beef samples, and values were 86.0-93.5 and 84.5-101.2%, respectively. The preparation of an immunochromatographic test strip based on gold nanoparticles was used for the rapid identification of imidocarb in milk and beef samples. When assessed by the naked eye, the visual LOD for imidocarb in milk and beef samples was 5 and 10 ng/mL, and the cut-off values were 20 and 50 ng/mL, respectively. Because of its high sensitivity, specificity, and simplicity, the test strip can be used for on-site testing and rapid screening of imidocarb in food samples.

Amarogentin (AG), a biologically active secoiridoid glycoside, is responsible for the efficacy of Gentianaceae based medications. Thus, qualitative and quantitative analyses of AG are of significance for batch to batch quality control purposes. By conjugating colloidal gold nanoparticles with the AG-specific monoclonal antibody, MAb 1E9, we were able to develop a single-step competitive immunochromatographic assay (ICA) for simple quantification of the AG content in plant samples. With a limit of detection of 250 ng/mL, the analytical results were obtained after immersing the ICA test strip in the detection mixture for 15 min. This new ICA is superior to conventional ICAs as it is considerably faster due to the speed with which the test strips can be produced and the omission of the time-consuming preparation phase that was previously required to make the fiber pad. Moreover, our ICA only needs a small amount of analyte (20 µL).The reliability of the reported test strip was confirmed by comparing its semi-quantitative results with those obtained via an indirect competitive enzyme-linked immunosorbent assay (icELISA). The positive correlation between these methods (R

We optimize the procedure for synthesizing gold nanoshells for their use as a sensitive label in an immunochromatographic assay (ICA). An immunochromatographic test system is developed to visually determine the concentration of an early cardio marker, a heart-type fatty acid-binding protein (H-FABP). Visual detection yields the detection limit of the procedure with gold nanoshells to be more 50% lower than that of gold nanoparticles; it is 0.5 ng/mL for H-FABP.

Rapid and portable detection of saxitoxin (STX) and its many congeners is highly desirable to prevent paralytic shellfish poisoning due to red tide or harmful algal blooms. In this work, we describe successful preliminary efforts to develop a very sensitive general STX family test strip employing highly fluorescent red quantum dots (Qdot 655) to detect as little as 0.5 to 1 part per billion (ppb or ng/ml) of STX with a dynamic range extending to 20,000 ppb after the prototype dipstick assay was optimized. A competitive format was necessitated by the small molecule nature of STXs having only one epitope, but the decrease in Qdot fluorescence was clearly visible to the naked eye as a function of increasing STX concentration in aqueous buffer. The competitive displacement assay format required conjugation of a primary amine in STX to carboxyl-Qdot 655 via a covalent carbodiimide coupling reaction which was validated by an electrophoretic mobility band shift assay.

In this study, a high sensitivity and specificity monoclonal antibody (mAb) was developed based on the hydroxy and carboxy-termini of ochratoxin A (OTA). A fluorescent microsphere immunochromatographic test strip (FM-ICTS) was assembled for the rapid detection the OTA in rice flour. Some relevant parameters were optimized including the best concentration of coating antigen and optimal diluent buffer composition. Under optimal conditions, the strip assay had a visual limit of detection (LOD) of 2 ng/mL and a cut-off value of 16 ng/mL for OTA in rice flour samples. By means of a strip scan reader, we obtained a quantitative measurement for OTA with an LOD of 1.27 ng/mL. No significant difference in the strip test results was seen when compared to an ic-ELISA assay or LC–MS/MS. This also shows, therefore, that the FM-ICTS has potential application for rapid and accurate quantitative detection in the market place.

In this study we developed a rapid and simple assay to detect RFP in fish using an immunochromatographic assay. We produced a sensitive and selective monoclonal antibody against RFP with a half-maximal inhibitory concentration (IC50) of 10.7 ng/mL. Fish samples were extracted with ethyl acetate, then centrifuged at 8000 rpm for 10 min, and concentrated by drying over nitrogen. We found under optimal conditions, that the RFP cut-off limits for the test strip was 10 µg/mL in both 0.01 M phosphate buffered saline and fish samples, and each test could be completed within 5 min. Therefore, immunochromatographic test can be used as a reliable, rapid, and sensitive method for the detection of RFP in fish.

A monoclonal antibody (mAb) against vitamin B1 was prepared and based on this, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and colloidal gold-based immunochromatographic test (ICT) strip were developed. The 50% inhibition concentration (IC50) and the limit of detection (LOD) for the developed ic-ELISA were estimated to be 20.71 ng mL−1 and 4.51 ng mL−1 in the assay buffer. Vitamin B1 in energy drinks, vitamin tablets, and infant milk powder samples was detected by the developed ic-ELISA and the average recoveries ranged from 80.63% to 103.05%. The vitamin B1 content in energy drinks, vitamin tablets, and infant milk powder samples were confirmed by using liquid chromatography tandem mass spectrometry (LC-MS/MS). Moreover, the cut-off value of the developed ICT strip assay was 250 ng mL−1, with a LOD value of 5.33 ng mL−1. Real samples were used to validate the reliability of the developed ICT strip. All results demonstrated that our developed methods are suitable for the detection of vitamin B1 in food and pharmaceutical products.

We have developed a sensitive and rapid gold nanoparticle-based immunochromatographic strip (GNP-ICS) for the detection of phenacetin (PNCT) and paracetamol (PAP) using an anti-PNCT monoclonal antibody (mAb). The sensitive anti-PNCT mAb (2D6) had a half maximal inhibitory concentration (IC50) and limit of detection (LOD) of 3.51 and 0.21 ng mL-1, respectively. Additionally, its cross-reactivity with PAP was approximately 10.1%. The developed GNP-ICS assay based on GNP-labeled mAb was sensitive for the detection of PNCT with vLOD and cut-off values of 2.5 and 50 ng mL-1 respectively and a vLOD value of 25 ng mL-1 for PAP. Furthermore, the developed icELISA and GNP-ICS assays were applied to determine PNCT-spiked beverage samples without pretreatment, in addition to a kind of PAP-containing drug. The recoveries were validated using high performance liquid chromatography (HPLC). The results revealed that the developed GNP-ICS assay was reliable for the detection of PNCT in practical samples.

Various nanodispersed markers and their combinations for immunochromatography with colorimetric and fluorimetric detection are considered and their opportunities for lowering the detection limit are characterized. The influence of the composition of antibody-nanomarker conjugates on analytical parameters of the test systems is described.

—An immunochromatographic test system for the combined analysis of two cardiomarkers, such as fatty acid binding protein (FABP) and troponin I (TnI), in serum and whole blood is developed. The main stages of the design of a multiparametric system are investigated, including the influence of the antibody position and gold nanoparticle size on the results. The detection limits of the method are found to be 10 ng/mL for FABP and 1 ng/mL for TnI, and the coefficient of variation did not exceed 10%. The developed test system allows us to confirm the diagnosis of acute myocardial infraction (N = 9). The analysis time is 15 min.

Near-infrared fluorescence immunoassay has been widely studied in the bio analytical field. This review mainly introduces the basic principles of near-infrared spectroscopy and near-infrared detection technology, and summarizes the properties, characteristics and recent improvement of optical properties and signal intensity of three near-infrared fluorescence probes (i.e. organic fluorophores, quantum dots and rare earth compounds). We describe the applications of near-infrared fluorescence technology in immunoassay, and prospect the application potential of lateral flow assay (LFA) based on this probe in the rapid detection of pathogens. Our team intends to establish a new platform which has highly sensitive near-infrared fluorescence probes (NIFPs) combined with portable and simple immunochromatographic test strips (ICTSs) for rapid detection of food borne viruses. This will provide technical support for a rapid detection on the port.

An anti-rosiglitazone (RSG) monoclonal antibody (4G6) was prepared to develop an immunochromatographic strip for the detection of illicitly added RSG in hypoglycemic functional foods. The monoclonal antibody was highly specific for RSG, with a half-life inhibitory concentration (IC50) of 1.0889 ng mL−1. Its limit of detection was 0.2178 ng mL−1 with a linear detection range of 0.2178–1.742 ng mL−1. The cut-off values of colloidal gold-based immunochromatographic test strips in phosphate buffered saline and functional food samples were both 10 ng mL−1. In the spiked samples and recovery tests, the recovery ranged from 96.58% to 101.68%. The results obtained by the immunochromatographic assay were consistent with those obtained by indirect competitive-ELISA. Therefore, our developed immunochromatographic strip system is suitable for the on-site detection and rapid screening of RSG in food samples.

Deoxynivalenol (DON) and zearalenone (ZEN) are mycotoxins that contaminate a wide range of grains and crops. In this study, a one-step time-resolved single-channel immunochromatographic test strip based on europium ion polystyrene fluorescence microspheres was first developed for sensitive and quantitative detection of DON and ZEN. The concentration of the artificial antigen and the mass ratio of the monoclonal antibody to fluorescent microspheres for conjugation were optimized to simplify the sample addition process during immunochromatographic assay and improve the on-site detection efficiency. The limits of detection (LOD) of the single-channel immunochromatographic test strip for DON and ZEN detection were 0.17 and 0.54 μg/L, respectively. Meanwhile, the dual-channel immunochromatographic test strip was designed to simultaneously detect DON and ZEN, with LODs of 0.24 and 0.69 μg/L achieved for DON and ZEN, respectively. The developed test strips also yielded recovery results consistent with that obtained by LC-MS/MS for DON and ZEN detection in real samples of wheat and corn flour, confirming the practicability and reliability of the test strip. The developed immunochromatographic test strips realize quick and sensitive detection of DON and ZEN, exhibiting potential for broad applications in the point-of-care testing platform of multiple mycotoxins in agricultural products. Graphic abstract.

Introduction Avoidance of inhaled bird antigens is essential to prevent hypersensitivity pneumonitis disease progression. The aim of the present study was to develop a sandwich enzyme link immunoassay (ELISA) and an immunochromatographic test (ICT) and compare their ability to detect pigeon antigens in environmental samples. Methods An amplified sandwich ELISA using pigeon serum as a calibration standard and a ICT using gold-labeled anti-pigeon serum antibodies for the rapid detection of pigeon antigens in environmental samples were developed. Twenty-two different airborne samples were collected and analysed using both methods. Strip density values obtained with ICT were calculated and compared with the concentrations determined by the ELISA method for pigeon antigens. Strips results were also visually analysed by five independent evaluators. Results The ELISA method to quantify pigeon antigen had a broader range (58.4 and 10,112.2 ng/ml), compared to the ICT assay (420 to 3360 ng/ml). A kappa index of 0.736 (p < 0.0001) was obtained between the observers evaluating the ICT strips. The results of the ELISA and the relative density of the ICT showed a highly significant correlation (rs:0.935; p < 0.0001). Bland-Altman plot also confirmed excellent agreement between the two methods (mean difference: −1.626; p < 0.0001). Conclusions Since there was a good correlation between both assays, we can conclude that the rapid and simple ICT assay is a good and valid alternative, which does not require expensive equipment, for the validated ELISA technique., Graphical abstract Unlabelled Image, Highlights • Demonstrating antigen exposure is critical in the diagnosis and management of hypersensitivity pneumonitis. • An immunochromatographic test is compared with an ELISA method for the measurement of pigeon antigens in the environment. • The immunochromatographic test described was highly consistent with the validated ELISA and does not require specific skills. • This method may prove to be a useful tool for predicting the progression of bird-related hypersensitivity pneumonitis.

The ciprofloxacin (CIP) abuse has caused many problems threatening to human health. Here, we design the quantum dot microsphere (QDM) based immunochromatographic quantitative CIP test strip: when the sample under detection contains CIP, the QDM-monoclonal antibody (mAb) probes bound with the CIP and cannot be captured by CIP-bovine serum albumin (BSA) conjugation dispersed on the T lines, reducing the fluorescence intensities. These test strips can provide a low detection limit of 0.05 ng/mL and a wide linear detection range from 0.1 ng/mL to 100 ng/mL in high sensitivity and accuracy as well as good selectivity, reproducibility and stability. Moreover, a smartphone based test strip reader with the size of 85 mm × 48 mm × 44 mm is also fabricated using 3-D printing to automatically and quantitatively detect CIP. The whole process of CIP detection can be finished within 15 min, but only cost ~1 RMB (10 cents).

The presented study is focused on the impact of binding zone location on immunochromatographic test strips on the analytical parameters of multiplex lateral flow assays. Due to non-equilibrium conditions for such assays the duration of immune reactions influences significantly the analytical parameters, and the integration of several analytes into one multiplex strip may cause an essential decrease of sensitivity. To choose the best location for binding zones, we have tested reactants for immunochromatographic assays of lincomycin, chloramphenicol, and tetracycline. The influence of the distance to the binding zones on the intensity of coloration and limit of detection (LOD) was rather different. Basing on the data obtained, the best order of binding zones was chosen. In comparison with non-optimal location the LODs were 5&ndash, 10 fold improved. The final assay provides LODs 0.4, 0.4 and 1.0 ng/mL for lincomycin, chloramphenicol, and tetracycline, respectively. The proposed approach can be applied for multiplexed assays of other analytes.

In this article, we describe an immunochromatographic test system developed for rapid serodiagnostics of cattle brucellosis using two markers: Gold nanoparticles (GNPs) and quantum dots (QDs). The test system was compared with immunochromatographic serodiagnostics systems that use only one marker. The approbation of the test system was conducted on samples of cattle sera with low, but diagnostically significant titers of specific antibodies. We show that when two conjugates are used, the intensity of the detectable signal increases by 2&ndash, 3 times compared with the test system using the QD conjugate and by more than nine times compared with the system using the GNP conjugate.

To improve viral antibody detection and disease control, laboratories need faster and simpler methods for direct detection of H9AIV in clinical samples. In this study, test strips were developed for rapid detection of H9AIV antibodies in poultry serum by a sandwich method with double-line detection. The hemagglutinin protein was labeled with colloidal gold as a detection reagent and was blotted on the test lines, while goat anti-rabbit IgG was utilized on the control line of the nitrocellulose membrane. The test strips have high specificity, sensitivity, and stability, with a correlation coefficient of 0.9656 and coefficients of variation below 10%. Application of the kit to quantitative detection of H9AIV antibodies in 504 samples collected from chickens showed a coincidence rate of 80.56% with previously run HI assays.

The traditional immunochromatographic assay using a conjugate of gold nanoparticles with specific ochratoxin A (OTA) antibodies and a new type of assay with indirect labeling using a combination of free antibodies and a conjugate of gold nanoparticles with anti-species antibodies were compared using the example of OTA detection. In the proposed assay, specific antibodies are included in the sample dilution buffer, which increases the duration of their interaction with the antigen, while a conjugate of anti-species antibodies with the marker is applied to the test strip. The assay was approbated for OTA detection in maize extracts. Transition to indirect labeling was shown to reduce the OTA detection limit by two orders of magnitude up to 0.12 ng/mL. The causes of this improvement are discussed. The high sensitivity of immunochromatography with indirect labeling makes it a promising approach for detection of various antigens with low molecular weight.

A rapid, simple, sensitive immunochromatographic strip test was developed to detect penbutolol (PB) in pig urine based on a sensitive and specific monoclonal antibody produced in our laboratory. The antigen (PB-ovalbumin) and a goat anti-mouse IgG antibody were drawn onto a nitrocellulose membrane as the test line and control line, respectively. Under optimised conditions, the semi-quantitative test strip detected PB at concentrations of 2.5 ng/mL in 0.01 M PBS (pH 7.4) and 0.5 ng/mL in pig urine. All results were obtained within 5 min. Our data indicate that this immunochromatographic assay can be used for the sensitive, rapid, and specific on-site screening of PB.

One of the major concerns in the application of nanocarriers in biosensing is the impair of the recognition molecules bioactivity loaded on their surfaces due to harsh and laborious cross-linking and random orientation, resulting in unsatisfactory sensitivity. Herein, we proposed a novel immunochromatographic test strip (FNS-ag-DICTS) by taking advantage of the antigen (ag) modified Fe2O3 nanostructures (FNSs) as new signal tags and goat anti-mouse IgG labeling on the detection line instead of ag, which was used for sensitive detection of aflatoxin B1 (AFB1). The fabricated FNS-ag can orientate the Fab region of monoclonal antibodies (mAbs), waiving the intrinsic limitations of traditional nanomaterials labeled mAbs. Under optimal conditions, FNS-ag-DICTS possessed excellent specificity and a wide detection range, with a visual limit of detection (vLOD) of 0.0125 ng mL−1. In addition, the biosensor successfully detected AFB1 in peanut, green bean and corn, with an average recovery rate of 82.8–124.9%.

The scheme of immunochromatographic competitive analysis with "external" specific antibodies is offered for the first time. The test strip includes all the necessary components for analysis (membranes, protein antigen conjugates, colored nanoparticles), except specific free unconjugated antibodies that are transferred to the buffer used for sample dilution. Thus, the concentrations of the antibodies and markers can be chosen independently, and dilution of the sample with buffer (a routine procedure for any immunochromatographic test) ensures pre-incubation of the antibodies with the sample. Both factors increase the sensitivity of the test. The proposed scheme has been proven to be effective for the determination of deoxynivalenol and T-2 toxin; detection limits of 500pg/mL and 50pg/mL, respectively, were achieved. This is an order of magnitude lower than the limits of detection of traditional tests using the same reagents. The analysis was conducted in water-organic extracts (20% methanol); the duration of the analysis is 10min (it's the same time as for a traditional test). The proposed approach is universal, and it can be used to detect a variety of compounds.

Methods for increasing the sensitivity of immunochromatographic test systems for the determination of low molecular weight analytes are proposed. The developed analysis schemes were tested in the determination of sulfonylamide and chloramphenicol in honey.

The authors describe a multicolor immunochromatographic test strip format for simultaneous detection of Vibrio cholera O1 (Ogawa) and of the Clostridium botulinum toxin type A. Respective monoclonal antibodies were conjugated to CdTe quantum dots (QDs) with green and orange emission color. Activated dextran is used as a cross-linker. The CD labeled antibodies were then covered with denatured reduced BSA (dBSA-QD). Under illumination, the test gives lines with emission peaks at 540 nm and 570 nm, respectively. This lateral flow assay system can detect V. cholerae down to 1000 cfu·mL−1 levels, and C. botulinum toxin down to 0.8 ng·mL−1. The method allows assays to performed within 10 min without any sample pretreatment.

Highly sensitive immunochromatographic test systems were developed for the detection of zearalenone (ZEA) and T-2 toxin (T2T) using magnetite nanoparticles (MNPs) for the labeling. In order to detect an analyte with high sensitivity, the competitive reaction was performed with free specific antibodies, while immune complexes were detected by the reaction with label-conjugated anti-species antibodies. The conditions for the synthesis of magnetite nanoparticles conjugated to anti-species antibodies were optimized. The concentrations of specific reagents that provided the highly sensitive detection of T-2 toxin and zearalenone were found. The instrumental detection limit for the determination of T-2 toxin and zearalenone in baby food samples (oat flakes) was 0.1 and 0.05 ng/mL (2.0 and 1.0 ng/g), respectively. The assay time was 15 min. The results of the present study confirm the possibility of the practical use of magnetite nanoparticles for immunochromatographic assay labeling.

A leteral-flow immunochromatographic assay was developed for the detection of papaverine (PAPA) in pure ginger powder samples. We produced a sensitive monoclonal antibody againsts PAPA (anti-PAPA mAb) by immunizing BALB/c mice with a well-characterized PAPA-keyhole limpet hemocyanin conjugate, produced in our laboratory. The coating antigen (PAPA-ovalbumin) and goat anti-mouse IgG antibody were used as the capture reagent in the control line of the test strip. Under optimized conditions, the cut-off limits of the test strip was 1 ng/mL in 0.01 M PBS (pH 7.4) and 5 ng/mL in pure ginger powder. The results were obtained within 5 min. The results revealed that the developed method is a sensitive, rapid, and simple tool for the detection of PAPA in pure ginger powder.

An amikacin-sensitive monoclonal antibody (MAb) assay and immunochromatographic test strip were developed and applied for the detection of amikacin residues in bovine milk and chicken eggs. The immunoassay was specific to amikacin and showed no cross-reactivity with other aminoglycosides. The half maximum inhibitory concentration (IC50) of the assay was 0.65 ng/mL and the results were obtained within 90 min. Recoveries from spiked food matrices were within the range of 73.55–84.61% for bovine milk and 73.70–105.75% for whole egg. The strip test results were obtained within 10 min and showed a visual detection limit of 5.0 ng/mL for both food matrices. These results show that the MAb immunoassay and strip test developed in this study are very specific to amikacin and sufficiently sensitive for detection and routine monitoring of amikacin residues in food.

Carbofuran is a highly toxic pesticide used in fruits and vegetables. In this study, we produced a specific and sensitive monoclonal antibody (mAb) which was prepared based on a hapten that was derivatized with benzofuranol against carbofuran. Following mice immunization and cell fusion, we obtained three monoclonal cell lines: 6D5, 3H2, and 3C6. The cell line 3H2 generated mAb with the highest affinity and sensitivity. The half maximal inhibitory concentration was 0.3 ng/mL, and the cross-reactivity was

A new technology to quantify phospho-p53 15 by converting its content to the amount of glucose which is detectable by a glucometer was developed. An immunochromatographic test strip (ITS) was used as a disposable platform, where primary antibody (Ab 1 )-modified Fe 3 O 4 magnetic nanoparticles (Fe 3 O 4 -Ab 1 ) were settled on the test zone to capture both the target phospho-p53 15 and the detection antibody (Ab 2 )-glucose encapsulating liposome (GEL) conjugate. The measurement was based on the release and subsequent detection of glucose from Ab 2 -GEL using a glucose meter (GM). The amount of glucose is proportional to the phospho-p53 15 concentration from 0.1 to 50 ng mL −1 , the limit of detection is 50 pg mL −1 (3S/N). The high sensitivity was a result of the huge number of glucose encapsulated in the liposome. Taking the advantage of low cost, widespread availability and portability of the test trip, together with the personal GM, the presented approach can be easily used to detect other disease biomarkers in medical diagnostics and environmental monitoring.

A rapid, simple, and sensitive immunochromatographic strip test has been developed to detect aldicarb (ALD) in 0.01 M phosphate buffer solution (PBS) (pH 7.4) and cucumber samples. The test was developed with a sensitive monoclonal antibody specific for ALD, generated by immunizing BALB/c mice with a well-characterized ALD – keyhole limpet hemocyanin conjugate, produced in our laboratory. Under the optimized condition, the cut-off limits of test strip for ALD were found to be 25 ng/mL in 0.01 M PBS (pH 7.4) and 100 ng/mL in cucumber samples, and the highest standard relative deviation was 9.05%. Both results were obtained within 5 min. The data indicate that the method is sensitive, rapid, and specific, so this immunochromatographic test strip has utility for the rapid high-throughput screening of the pesticide, especially in food samples.

A rapid and sensitive immunochromatographic test strip (ICTS) was developed in a competitive format with the quantum dot-conjugated monoclonal antibody specifically to determine the residues of oxytetracycline (OTC) and its metabolite 4-epi-oxytetracycline (4-epi-OTC). Using an ICTS reader, the 50% inhibition concentration (IC

Three types of nanoparticles, quantum dots (QDs), gold particles (GPs), and latex particles (LPs), were compared as labels for immunochromatographic assay. The influence of the nature of the label on the analytical performance of the test systems was studied using the example of detection of the antibiotic chloramphenicol (CAP). The limits of detection of CAP are 0.1 ng/mL for QDs, 2.4 ng/mL for GPs, and 0.3 ng/mL for LPs. The unique structure and physical properties of the QD fluorescent labels ensure their competitive advantage over colorimetric labels. The proposed methodology is applicable to determination of characteristics of other nanodisperse labels.

Nanogold enhanced surface plasmon resonance (SPR), colloidal gold immunochromatographic test strips (ICTS), and polymerase chain reaction (PCR), combined with immunomagnetic separation (IMS) were established in this study for the rapid detection of Vibrio parahaemolyticus (VP). The sensitivities of SPR, ICTS, and PCR was determined to be 101, 103, and 103 CFU/mL for VP, respectively. After separation and enrichment by IMS, the sensitivities of SPR, ICTS, and PCR were 100, 101, and 102 CFU/mL for VP, respectively, which were improved by 10-, 100-, and 10-fold compared to the direct detection by SPR, ICTS, and PCR, respectively. When the VP-polluted water samples were directly assessed by SPR, ICTS, and PCR, the results were negative. By contrast, after separation and enrichment for 45 min by IMS, the results were all positive. The IMS-SPR, IMS-ICTS, and IMS-PCR detection methods were able to yield results in approximately 1.5 h, 55 min, and 3.5 h, respectively. These combined detection methods have advantages in being high-throughput and easy to operate without the need for sophisticated equipment or specialized skills. These methods might aid in the development of SPR, ICTS, and PCR technologies for simultaneously examining multiple food-borne pathogens in food products.

Determination of concentration of cortisol in various biological fluids can provide extensive information about a person’s health. Historically, cortisol and its derivatives were (and still are) determined using immunoaffinity-based methods such as colorimetric ELISA assay, chemiluminescent immunoassay, fluorescence assays, radioimmunoassay, electrochemiluminescence immunoassay, immunochromatographic test, or sensors and immunosensors. Recently, mass spectrometry (MS)-based methods started to be used in determination of cortisol and its derivatives. These MS methods are net superior to immunoaffinity-based assays, but are not easily applicable and are also time-consuming and price prohibitive. Furthermore the standard MS instruments used are triple quadrupole instruments. Here we review the literature on the MS and non-MS based methods for determination of cortisol and its derivatives and also explore the use of a less used quadrupole-time of flight instrument in determination of these compounds.

This chapter introduces enzyme-linked immunosorbent assay and colloidal gold immunochromatographic strip test. Specifically, it includes the preparation of monoclonal antibody. The principle, classification, and operation steps of enzyme-linked immunosorbent assay based on monoclonal antibody were highlighted. The working principle of colloidal gold immunochromatographic test strip was also introduced detailedly.

This chapter introduces the overview of pesticides containing the application, characteristics, mode of action, classification, hazard, and the maximum residue levels. Then, the synthetic procedures of pesticide haptens were depicted at length. The antibodies acquired by the forementioned hapten were the most sensitivity to date. Synthesis formats of antigen with various active groups were summarized. The cross-reactivities of antibody were analyzed via the enzyme-linked immunosorbent assay to provide the basis for hapten design. Additionally, authors also presented the pretreatment methods of different samples. Then, the colloidal gold-based immunochromatographic test strips for the determination of pesticides were described including the detection ranges and cutoff values. Finally, the perspective of immunoassays for pesticide analysis was discussed containing three parts: the introduction of computer-assisted molecular modeling, the development of the genetic engineering antibodies, and the application of nanomaterials in pesticide immunoassays.

The forensic investigation of sexual crimes includes the use of presumptive tests, which are based on the detection of semen components like the enzyme acid phosphatase (AP) and the prostate specific antigen (PSA). Because the forensic field usually deals with trace and old samples, the major goal of this study is to evaluate the sensitivity and specificity of semen presumptive tests which have a specific forensic purpose, such as the colorimetric test kit SERI AP Spot Test and the immunochromatographic test kit SERATEC PSA Semiquant. To achieve this goal, samples containing saliva, semen, vaginal fluid, and mixtures were tested. The results of the AP Spot test indicate that the two minutes that limit the reaction time to avoid false-positive can be insufficient for detection of trace and old samples. The results of the PSA Semiquant suggest that this test is more sensitive and specific to semen detection than the AP test. Therefore, this study reassures the importance of presumptive tests as screening tests.

Immunochromatographic test strip (ITS) for point-of-care testing (POCT) has attracted prominent attention due to the advantages including rapid response, low cost and good portability. Here, we developed a sensitive ITS for detecting aflatoxin B1 (AFB1) by using dendritic platinum nanoparticles (DPNs) as novel pressure/colorimetric dual-readout probes. DPNs-labeled antibody of AFB1 were used as the signal tracer of the immunochromatographic process. After 10-min competitive immunoreaction, black color appeared on the test line of ITS due to the accumulation of DPNs, which was observed visually as a colorimetric readout for qualitation purpose. Furthermore, DPNs with peroxidase-like activity caused decomposition of hydrogen peroxide aqueous solution to produce pressure change signal in vials, which was detected by a hand-held pressure meter for quantitation purpose. With the pressure readout mode, the detection range was 0.05–10 ng mL−1, and the detection limit was 0.03 ng mL−1 (S/N = 3) for AFB1. The proposed ITS was successfully utilized for detecting AFB1 in herbal medicine samples, and the acceptable recoveries of 93.77–114.09% indicated the reliability for real sample detection. It provides a new avenue for POCT with great application potential in various area including drug and food quality control, pollutants monitoring as well as medical diagnosis.

In recent years, the undeclared presence of various anabolic androgenic steroids (AAS) in commercial supplements has been confirmed. This fact can be a potential threat to all athletes using these supplements, and therefore, there is of increased interest in the implementation of rapid methods for the detection of AAS. The presented study describes the development of an immunostrip test for the detection of multiple 17α-methylated AAS based on direct and indirect competitive principle using gold nanoparticles as a label. As a capture reagent on test lines conjugated stanazolol to rabbit serum albumin (RSA/ST-3) was used, the intensity of color formed in the test line of the AAS-positive sample was visually distinguishable from that of negative sample within 10 min. The optimized closed direct and indirect format of the test provided a similar visual detection limit (0.7 and 0.9 ng/mL, respectively). The most commonly orally abused AAS (17α-methyltestosterone, methandienone, methyldihydrotestosterone, oxandrolone and oxymetholone) showed a strong cross-reaction. Developed immunostrips were successfully applied to analysis of artificially contaminated dietary supplements with 17α-methylated AASs. The developed immunostrips offer potential as a useful user-friendly method for capturing suspicious dietary supplement samples with different contents of AAS at levels far below the usually used concentrations of AAS.

Herein, a label-free and dual-readout immunochromatographic test strip (ITS) for the sensitive detection of Escherichia coli (E. coli) O157:H7 by taking advantages of the strong capture ability of Fe3O4@CuS nanostructures (NSs) towards bacteria and their ultrahigh photothermal effects (PTEs) was reported. Especially, without the customarily antibody (Ab)-labeled probe, Fe3O4@CuS NSs could be adsorbed onto the surfaces of bacteria to form Fe3O4@CuS-bacteria conjugates and then trapped by immobilized Abs on the test line (T-line), forming a characteristic yellow band. After direct immunoreactions, the PTEs of Fe3O4@CuS NSs endowed T-line to be irradiated by an 808 nm infrared light, obtaining satisfactory sensitivity and accuracy. Under optimal conditions, E. coli O157:H7, as low as 103 and 102 CFU/mL, could be monitored in colorimetric and photothermal modes. Additionally, E. coli O157:H7 was successfully detected in beef, chicken, milk and honey samples by this proposed platform with a recovery of 80–120%.

Fumonisins are a kind of toxic and carcinogenic mycotoxin. A rapid immunochromatographic test strip has been developed for simultaneous detection of fumonisin B1 , B2 and B3 (FB1 , FB2 and FB3 ) in maize based on colloidal gold-labelled monoclonal antibody (McAb) against FB1 probe.; Results: The anti-FB1 McAb (2E11-H3) was produced through immunisation and cell fusion, and identified as high affinity, specificity and sensitivity. The cross-reaction ratios with fumonisin B2 and B3 were accordingly 385% and 72.4%, while none with other analogues. The colloid gold-labelled anti-FB1 McAb probe was successfully prepared and used for establishing the immunochromatographic strip. The test strip showed high sensitivity and specificity, the IC50 for FB1 was 58.08 ng mL-1 , LOD was 11.24 ng mL-1 , calculated from standard curve. Moreover, the test strip exhibited high cross-reactivity with FB2 and FB3 , and could be applied to the simultaneous detection of FBs (FB1 :FB2 :FB3 = 12:4:1) in maize sample with high accuracy and precision. The average recoveries of FBs in maize ranged from 90.42% to 95.29%, and CVs were 1.25-3.77%. The results of the test strip for FBs samples showed good correlation with high-performance liquid chromatography analysis.; Conclusion: The immunochromatographic test strip could be employed in the rapid simultaneous detection of FB1 , FB2 and FB3 in maize samples on-site. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

Novel direct and indirect competitive fluorescence-linked immunosorbent assays (cFLISA and icFLISA) for detection of ochratoxin A (OTA) were described using CdTe quantum dots (QDs) as fluorescent label. CdTe QDs were successfully synthesized, which had an emission wavelength of 615 nm. The high purity monoclonal antibody against OTA was prepared through cell thawing and the octylic acid-ammonium sulfate method. The OTA MAbs were successfully coupled with CdTe QDs, and which also retained the original biological activity. The 50% inhibition values (IC50 ) of the cFLISA and icFLISA were 0.630 ng/mL, 0.234 ng/mL, the limits of detection (LOD) were 7.06 × 10-3 and 4.15 × 10-3 ng/mL, and detection ranges were 7.06 × 10-3 - 18.34 ng/mL and 4.15 × 10-3 - 4.88 ng/mL, in-order. The recoveries were 96.0-104.7% along with coefficients of variation (CVs) below 10%. The FLISA provided novel method for determination of OTA and the potential of MAb-CdTe QDs for the establishment of fluorescent immunochromatographic test strip.

Salbutamol (SAL), a kind of β-agonist which can enhance the lean meat-to-fat ratio, has been inhibited as an additive used in animal feeds for livestock production in many countries due to its harmful effect to the consumers. In this study, an ultrasensitive and specific competitive immunochromatographic test (ICT) integrated with surface-enhanced Raman scattering (SERS) for the detection of SAL was described. The immunoprobe was prepared by immobilizing polyclonal antibody against SAL on the surface of Au@Ag nanoparticles in which the Raman reporter (4-mercaptobenzoic acid, MBA) had been sandwiched. After ICT procedures, the specific SERS signals generated from MBA on the test line of the ICT strip were measured for the quantitative determination of SAL. The assay was completed in 15 min. The IC50 and the limit of detection (LOD) values of the assay for SAL were 0.028 ng mL−1 and 3.0 pg mL−1, respectively. There was no cross-reactivity (CR) of the assay with other three β-agonists (clenbuterol, phenylethanolamine A, and ractopamine), showing high specificity of the assay. Spiking experiments indicated that the average recoveries (n = 3) of SAL from swine feed, meat, and urine samples were in ranges of 98.4–105.2 % with the relative standard deviations (RSDs) of 1.7–7.8 %. The results demonstrated that the proposed ICT was a feasible method for ultrasensitive and specific detection SAL in swine feed, meat and urine samples, and could be extended for the detection of other target analytes.

ENR and OFL are the most consumed quinolones on livestock in China. In this work, we developed a rapid immunochromatographic lateral flow test strip for simultaneous detection of the residues of enrofloxacin and ofloxacin in chicken muscle and pork. We screened an anti-ENR and OFL monoclonal antibody. The IC50 of anti-ENR and anti-OFL were 6.67 and 7.13 ng/ml, respectively. The present immunochromatographic lateral flow test strip is a one-step assay and required much less professional personnel and experimental instruments. In the present study, the decision limit (CCα) of the test strip was calculated to be 0.089 ng/mL and detection capability (CCβ) was 0.217 ng/mL with the scanner. The limit of detection was estimated to be 10 ng/mL. According to parallel HPLC analysis with 47 blind samples, coincidence rate is 100 % when the contents of ENR and OFL were more than 10 ng/mL. Results indicated that the strip test we developed had good reliability, and the strip test gave neither false positive nor false negative results. It will provide results within 20 min without special equipment. Therefore, the test strip is very useful as a screening method for semi-quantitative or qualitative detection of enrofloxacin and ofloxacin in chicken muscle and pork.

A sensitive indirect competitive enzyme-linked immunosorbent assay(ic-ELISA) method and a gold nanoparticle immunochromatographic strip were developed to detect amantadine (AM) in foods. A novel AM hapten was prepared, and a sensitive monoclonal antibody against AM was developed. The optimum ic-ELISA conditions included a pH of 7.4 and an ionic strength of 1.6% with no organic solvents. The half-inhibition concentration (IC50) value of ic-ELISA was 1.92 ng/ml, with a limit of detection of 0.62 ng/ml. The immunochromatographic test strip method had a visual cut-off value at 5 μg/kg. Chicken samples were spiked with three concentrations of AM (1, 2, and 5 µg/kg) and analysed by ic-ELISA. Good recoveries were obtained (92.3% at 1 µg/kg AM, 116.1% at 2 µg/kg AM, and 91.8% at 5 µg/kg AM).