Rapid Simultaneous Detection of Anti-protozoan Drugs Using a Lateral-Flow Immunoassay Format

A facile and intelligent detection method for diclazuril based on a stable dual emissive Eu3+-dopped metal-organic framework

Diclazuril (DIC) is a broad-spectrum anti-coccidiosis drug of the triazine class, widely used in poultry farming. The overuse of DIC may lead to its accumulation in animal bodies, which may enter the food chain and threaten human health. In this work, we fabricated a stable Eu3+-doped UiO-66 fluorescence sensor (EuUHIPA-30) for the sensitive detection of DIC. Among 20 veterinary drugs, the fluorescence of EuUHIPA-30 selectively responds to DIC, with a low detection limit (0.19 μM) and fast response (10 s). EuUHIPA-30 is recyclable and can detect DIC in chicken and eggs with good recoveries. Moreover, a smartphone-integrated paper-based sensor enables the instrument-free, rapid, visual, and intelligent detection of DIC in chickens and eggs. This work provides a promising candidate for practical fluorescent DIC sensing in animal-derived food to promote food safety.

Generation and Characterization of an Anti-diclazuril Monoclonal Antibody and Development of a Diagnostic Enzyme-Linked Immunosorbent Assay for Poultry

An anti-diclazuril monoclonal antibody (mAb) was developed for use in enzyme-linked immunosorbent assay (ELISA)-based detection of diclazuril with high sensitivity and specificity, which can be used to measure anti-coccidial drug residues. The anti-diclazuril mAb had a half-maximal inhibitory concentration of 0.449–0.517 ng/mL. The mAb cross-reactivity with toltrazuril, toltrazuril 18 sulfone, clozaril, monesin, madurmycin, and salinomycin was very minimal (< 0.1%). The detection limit of the ELISA using this mAb was 0.10 ng/mL and the sensitivity was 0.05 ng/mL. A standard curve generated in the range of 0.05–16.2 ng/mL had a linear correlation coefficient value of ≥ 0.99. The average recoveries of diclazuril from chicken and duck samples ranged from 85.0 to 102.5%.Intra- and inter-assay coefficients of variation ranged from 5.9 to 8.5% and 9.2 to 12.6%, respectively. Using the International Immunogenetics Information System^®, the VH domain of the mAb was found to be encoded by an IGHV3 family gene and had the following complementarity determining region (CDR) sequences: GFTFSRY (CDR1), SRGGS (CDR2), and GDDNYAFAY (CDR3). The VL domain was encoded by an IGKV1 family gene and had the following CDR sequences: KSSQSLLNSRTRKNYLA (CDR1), WASTRES (CDR2), and KQSYNLHT (CDR3). This study provides a method to generate anti-diclazuril mAbs and determine their variable region sequences. The diagnostic ELISA developed using this mAb may drive additional studies on the monitoring and detection of food and veterinary drug residues.

Switching from Multiplex to Multimodal Colorimetric Lateral Flow Immunosensor

Multiplex lateral flow immunoassay (LFIA) is largely used for point-of-care testing to detect different pathogens or biomarkers in a single device. The increasing demand for multitargeting diagnostics requires multi-informative single tests. In this study, we demonstrated three strategies to upgrade standard multiplex LFIA to multimodal capacity. As a proof-of-concept, we applied the strategies to the differential diagnosis of Human Immunodeficiency Virus (HIV) infection, a widespread pathogen, for which conventional multiplex LFIA testing is well-established. In the new two-parameter LFIA (x2LFIA), we exploited color encoding, in which the binding of multiple targets occurs in one reactive band and the color of the probe reveals which one is present in the sample. By combining the sequential alignment of several reactive zones along the membrane of the LFIA strip and gold nanoparticles and gold nanostars for the differential visualization, in this demonstration, the x2LFIA can furnish information on HIV serotype and stage of infection in a single device. Three immunosensors were designed. The use of bioreagents as the capturing ligand anchored onto the membrane or as the detection ligand labelled with gold nanomaterials affected the performance of the x2LFIA. Higher detectability was achieved by the format involving the HIV-specific antigens as capturing agent and labelled secondary bioligands (anti-human immunoglobulins M and protein G) as the probes.

One-step icELISA developed with novel antibody for rapid and specific detection of diclazuril residue in animal-origin foods

Diclazuril, a broad-spectrum anticoccidial drug, may be accumulated in edible tissues of animals through illegal use, which poses potential threats to human health through the food chain. In this study, an innovative hapten was designed and an immunogen of diclazuril was successfully synthesised with keyhole limpet haemocyanin as carrier protein; then a monoclonal antibody with high specificity was obtained. Furthermore, based on the novel antibody, a one-step indirect competitive enzyme-linked immunosorbent assay (icELISA) was established for rapid and specific detection of diclazuril residues. Compared with the traditional icELISA method, this method saves at least 0.5 hours and one washing step. Under the optimal conditions, the one-step icELISA for diclazuril exhibited good performance with a 50% inhibition concentration (IC₅₀) value of 0.952 μg/kg. The average recoveries of the icELISA ranged from 73.1% to 115.5% with the coefficient of variation lower than 12.7%, which was evaluated by detecting spiked animal-origin food samples. Finally, the one-step icELISA shows a good correlation with an ultra-high liquid chromatography-tandem mass spectrometry method. Those results demonstrate that the one-step icELISA developed for diclazuril detection is time-saving, low-cost, specific, sensitive, and reliable. It shows good potential for social, environmental, and economic benefits in future use.

Rapid and sensitive detection of diclazuril in chicken samples using a gold nanoparticle-based lateral-flow strip

In this study, we produced a sensitive and specific monoclonal antibody (mAb) against diclazuril based on a new hapten. The mAb, which belongs to the IgG2 subclass, had a 50%-inhibitory concentration of 0.36 ng/mL. A cross reactivity test revealed that the mAb had good specificity for diclazuril. A gold nanoparticle-based lateral-flow strip was assembled for the rapid screening of diclazuril in raw chicken breast and thigh samples. The strip assay had a visual limit of detection (LOD) of 2 μg/kg and a cut-off value of 20 μg/kg for diclazuril in chicken samples when evaluated with the naked eye. With the aid of a strip scan reader, the proposed assay obtained a quantitative measurement for diclazuril with an LOD of 1.08 μg/kg. Therefore, this gold nanoparticle-based lateral-flow strip assay represents a potentially useful tool for on-site detection and rapid initial screening of diclazuril in chicken samples.

Development of molecularly imprinted electrochemical sensor with reduced graphene oxide and titanium dioxide enhanced performance for the detection of toltrazuril in chicken muscle and egg

A molecularly imprinted electrochemical sensor for toltrazuril (TZR) detection based on molecularly imprinted polymers (MIPs) immobilized on reduced graphene oxide (rGO) and titanium dioxide (TiO₂) modified platinum (Pt) electrode surface was fabricated for the first time. The synergistic fast electron transfer ability, large electroactive surface area and high catalytic activity from rGO and TiO₂ contribute to amplify the electrochemical signal and consequently improve the sensitivity of the sensor. The cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) tests were used to evaluate the performance of the electrochemical sensor. The results showed that the electrochemical sensor possessed high sensitivity, good selectivity and anti-interference ability toward TZR. By using the DPV, the electrochemical sensor displayed a wide linear concentration range from 0.43 to 42.54 μg/L, with a limit of detection of 0.21 μg/L (S/N = 3). Moreover, the recoveries and relative standard deviations (RSD) were 85.0%-97.0% and 3.5%-6.4% at three concentration levels, respectively, implying that the established sensor is promising for the accurate detection of TZR at trace levels in chicken muscle and egg samples.

A colorimetric paper-based sensor for toltrazuril and its metabolites in feed, chicken, and egg samples

In this study, a sensitive monoclonal antibody (mAb) against toltrazuril (Tol) was developed based on a novel hapten. The 50% inhibitory concentrations (IC₅₀) of toltrazuril and its metabolites ranged from 2.19 ng/mL to 4.21 ng/mL. Based on this mAb, a colorimetric paper-based sensor was developed for the rapid screening of Tol and its metabolites in samples. The proposed assay has cutoff values of <20 μg/kg for Tol and 50 μg/kg for Tol sulfone when evaluated with the naked eye, and the results could be obtained in 15 min. Quantitative results were obtained with a strip scan reader, with limits of detection <2.60 μg/kg for Tol and its metabolites in real samples. The sensitivity of both qualitative and quantitative detection meets the European Union requirements. Therefore, this strip assay provides a useful tool for the on-site detection and rapid initial screening of Tol and its derivatives in feed, egg, and chicken samples.