Rapid detection of adulteration of dehydroepiandrosterone in slimming products by competitive indirect enzyme-linked immunosorbent assay and lateral flow immunochromatography

Simultaneous identification of three emergent stimulant laxative adulterants in slimming foods using only one antibody

Stimulant laxatives were recently found to be abused in slimming foods, resulting in harmful effects on consumers. To ensure the safety of relative products, sensitive yet multiplex immunoassays are crucial in rapid screening of stimulant laxatives. However, there are few immunoassays for these substances, and even less for broad-specific recognition. Thus, in this work, four theoretically promising haptens of emerging stimulant laxative bisacodyl were rationally designed using molecular modeling and synthesized to immune animals, whose feasibility was confirmed by the obtained broad-specific antibody. Based on this unique antibody, a highly sensitive multiplex competitive indirect enzyme-linked immunosorbent assay (ciELISA) was established with low limits of detection for bisacodyl, sodium picosulfate, and BHPM (0.23, 13.68, and 0.11 ng/mL). In spiked sample recovery test and real sample detection, this ciELISA exhibited acceptable consistency with the validation method, demonstrating high accuracy and applicability of our method. This reliable multiplex ciELISA proceeds the rapid screening of stimulant laxatives in slimming foods.

Magnetic-fluorescent immunosensing platform applying AuNPs heterogeneous MIL-53(Al) composite for efficient detection of zearalenone

Rapid, sensitive, specific and stable detection of mycotoxin in food remains an extremely crucial issue. Herein, a magnetic-fluorescent immunosensing platform for the detection of zearalenone (ZEN) was proposed. The platform utilized Au nanoparticles (AuNPs) heterogeneous fluorescent metal-organic framework (MIL-53(Al)@AuNPs) labeled with ZEN-bovine serum albumin (ZEN-BSA) as signal probe and ZEN mono-antibodies coupled with magnetic NPs (MNPs-mAbs) as capture probe. Specifically, the heterogenization of AuNPs on the MIL-53(Al) surface improved its biocompatibility, and facilitated the loading of ZEN-BSA conjugates. The MNPs-mAbs could rapidly capture the target ZEN, simplify the immunoassay process and further improve the detection efficiency. The established competitive magnetic-fluorescent immunosensing platform had a wider linear response to ZEN in the range of 0.001-100 ng/mL with a lower limit of detection (LOD) at 0.0035 ng/mL, and could finish the whole detection process within 20 min, showing great potential for rapid and sensitive detection of food contaminants.

Identifying fungicide difenoconazole as illegal growth regulator in vegetable: Computer-aided hapten similarity to enhance immunoassay sensitivity

Difenoconazole, a fungicide with broad-spectrum properties, has recently been found to have been used illegally used as a plant growth regulator in Brassica campestris, with the intent of inducing thick stems and dark green leaves. However, analysts have encountered challenges in implementing a rapid surveillance screening approach for this purpose. In this study, a novel hapten was designed to improve the analytical performance of difenoconazole immunoassay. Specifically, the triazole of the original hapten was replaced with a benzene ring, guided by molecular simulation. This led to the development of a very sensitive antibody and the subsequent development of a competitive indirect enzyme linked immunosorbent assay (ciELISA) for the detection of difenoconazole in vegetable samples. The assay exhibited a working range of 0.16 ng mL^-1 to 9.64 ng mL^-1, with a detection limit of 0.05 ng mL^-1. Upon analysis of blind samples, a strong correlation was observed between the ciELISA and HPLC-MS/MS methods. As a result, the proposed technique may prove to be an excellent tool for the rapid detection of difenoconazole overuse and adulteration in vegetables.

Global calibration for non-targeted fraud detection in quinoa flour using portable hyperspectral imaging and chemometrics

Quinoa is one of the highest nutritious grains, and global consumption of quinoa flour has increased as people pay more attention to health. Due to its high value, quinoa flour is susceptible to adulteration. Cross-contamination between quinoa flour and other flour can be easily neglected due to their highly similar appearance. Therefore, detecting adulteration in quinoa flour is important to consumers, industries, and regulatory agencies. In this study, portable hyperspectral imaging in the visible near-infrared (VNIR) spectral range (400-1000 nm) was applied as a rapid tool to detect adulteration in quinoa flour. Quinoa flour was adulterated with wheat, rice, soybean, and corn in the range of 0-98% with 2% increments. Partial least squares regression (PLSR) models were developed, and the best model for detecting the % authentic flour (quinoa) was obtained by the raw spectral data with R²p of 0.99, RMSEP of 3.08%, RPD of 8.77, and RER of 25.32. The model was improved, by selecting only 13 wavelengths using bootstrapping soft shrinkage (BOSS), to R²p of 0.99, RMSEP of 2.93%, RPD of 9.18, and RER of 26.60. A visualization map was also generated to predict the level of quinoa in the adulterated samples. The results of this study demonstrate the ability of VNIR hyperspectral imaging for adulteration detection in quinoa flour as an alternative to the complicated traditional method.

Establishment and application of multiple immunoassays for environmental estrogens based on recombinant Japanese flounder (Paralichthys olivaceus) choriogenin protein

Environmental estrogens have generated great concern because of their potential threat to aquatic organisms; however, the commonly used vitellogenin (Vtg) biomarker detection methods are not capable of detecting estrogenic activity below 10 ng/L 17β-estradiol. In this study, we developed multiple immunoassays based on Japanese flounder (Paralichthys olivaceus) choriogenin (Chg), a highly sensitive biomarker of environmental estrogens. Chg genes (ChgL and ChgH) of Japanese flounder were cloned for the first time, and a recombinant ChgL protein with a molecular weight of approximately 52 kDa was prepared using a prokaryotic expression system and purified using Ni-affinity column chromatography. Subsequently, specific monoclonal antibodies against ChgL were prepared and used to develop sandwich enzyme-linked immunosorbent assays (ELISAs), which had a detection range of 3.9-250 ng/mL and detection limit of 1.9 ng/mL. An immunofluorescence method was also established and used to visually detect ChgL induction in the tissues. In addition, a lateral flow immunoassay for ChgL that could detect estrogen activity within 10 min was developed. Finally, the reliability of the immunoassays was examined by measuring ChgL induction in the plasma and tissues of Japanese flounder exposed to 0, 2, 10, and 50 ng/L 17α-ethinylestradiol (EE₂). The results showed that 2 ng/L EE₂ notably increased ChgL levels in the plasma, demonstrating that ChgL is more sensitive than Vtg to environmental estrogens; 50 ng/L EE₂ induced obvious Chg induction in the sinusoidal vessels of the liver. Conclusions taken together, this study provides reliable methods for sensitive and rapid detection of estrogenic activity in aquatic environments.

Development of a highly sensitive immunoassay for detecting aminopyrine abuse in herbal tea

With the popularity of herbal tea in China, many food fraudsters have added illegal drugs to herbal tea to enhance its functions, among which aminopyrine is widely abused as an antipyretic and analgesic. Presently, there is no immunoassays for aminopyrine, and it is difficult to achieve real-time detection in the field. Based on a polyclonal antibody of aminopyrine with high specificity and sensitivity, an optimal combination of coating antigen/antibody was obtained by screening different coating antigens. On this basis, a sensitive ic-ELISA method was established to detect aminopyrine in herbal tea. The detection limit of the ic-ELISA was 0.18 ng mL^-1, which was much lower than the 100 ng mL^-1 required as a standard. The method had good consistency with LC-MS in the detection of actual samples and could be used as a reliable method for the detection of aminopyrine in herbal tea.

An Ultrasensitive Lateral Flow Immunoassay Based on Metal-Organic Framework-Decorated Polydopamine for Multiple Sulfonylureas Adulteration in Functional Foods

Herein, an ultrasensitive lateral flow immunoassay (LFIA), based on metal-organic framework-decorated polydopamine (PCN-224@PDA) was first established to detect multiple sulfonylureas (SUs) in functional foods. The PCN-224@PDA was synthesized using the one-pot hydrothermal method and covalently coupled with SUs antibodies, and the coupling rate was up to 91.8%. The detection limits of the developed PCN-224@PDA-LFIA for multiple SUs in functional teas and capsules were 0.22-3.72 μg/kg and 0.40-3.71 μg/kg, and quantification limits were 0.75-8.19 μg/kg and 1.03-9.08 μg/kg, respectively. The analytical sensitivity was 128-fold higher than that of similar methods reported so far. The recovery rates ranged from 83.8 to 119.0%, with coefficients of variation of 7.6-14.4%. The parallel analysis of 20 real samples by LC-MS/MS confirmed the reliability of the proposed method. Therefore, our work offers novel, ultrasensitive, and rapid technical support for on-site monitoring of SUs in functional foods.

Versatile Au@Ru nanocomposites for the rapid detection of Salmonella typhimurium and photothermal sterilization

In view of the current public health hazards of food-borne pathogens, it is urgent to develop a rapid detection method with high sensitivity, good specificity and operational convenience, as well as to determine an effective sterilization strategy. Herein, versatile gold-ruthenium nanocomposites modified with antibody (Au@Ru-pAb Ncs) have been constructed for the sensitive detection of Salmonella typhimurium (S. typhimurium) via the lateral flow immunochromatographic assay (LFIA). Au@Ru-pAb Ncs based LFIA exhibited a wide detection range from 2.9 × 10⁶ CFU/mL to 2.9 × 10¹¹ CFU/mL with the limit of detection of 9.8 × 10⁴ CFU/mL for S. typhimurium, and displayed excellent specificity. In addition, Au@Ru-pAb Ncs irradiated with 808 nm (500 mW/cm²) near-infrared light (NIR) had a significant antibacterial effect within only 5 min, attributed to its high photothermal conversion efficiency of 54.14%. Therefore, both sensitive detection of S. typhimurium and effective NIR-triggered photothermal sterilization were achieved by using versatile Au@Ru-pAb Ncs, showing great prospects in the field of pathogen detection and treatment.

Rapid, on-site quantitative determination of higenamine in functional food using a time-resolved fluorescence microsphere test strip

Higenamine (HIG), a benzyltetrahydroisoquinoline alkaloid found naturally in plants, is classified as an S3 Prohibited Substance in the 2020 World Anti-Doping Agency (WADA) report. To avoid problems such as doping violations in competitive events, it is necessary to develop rapid and sensitive detection methods. In this study, a highly-sensitive anti-HIG monoclonal antibody (mAb) was prepared and a time-resolved fluorescent microsphere immunochromatographic test strip (TRFM-ICTS) was established for the rapid quantitative detection of HIG in functional foods. Under optimized conditions, the TRFM-ICTS was compared with colloidal gold immunochromatographic test strip (CG-ICTS), and the half-maximal inhibitory concentration (IC₅₀) of TRFM-ICTS was 1.37 ng/mL. The spiked recoveries ranged from 86.4% to 105.3%, which was consistent with the results of liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the detection of real functional food. Therefore, TRFM-ICTS can be a candidate method for doping monitoring in functional foods and a powerful tool for HIG quantification.

Antibody Generation and Rapid Immunochromatography Using Time-Resolved Fluorescence Microspheres for Propiconazole: Fungicide Abused as Growth Regulator in Vegetable

Propiconazole (PCZ) is a fungicide popularly used to prevent and control wheat and rice bakanae disease, etc. However, it was recently found to be illegally employed as a plant regulator to induce thick stems and dark green leaves of Brassica campestris, a famous vegetable in Guangdong, South China. Due to a lack of available recognition molecules to the target analyte, it is still a big challenge to establish a rapid surveillance screening method. In this study, a novel chiral hapten was rationally designed, and an artificial immunogen was then prepared for the generation of a specific antibody against propiconazole for the first time. Using the obtained antibody, a highly sensitive time-resolved fluorescence microspheres lateral flow immunochromatographic assay (TRFMs-LFIA) was established with a visual limit of detection of 100 ng/mL and a quantitative limit of detection of 1.92 ng/mL for propiconazole. TRFMs-LFIA also exhibited good recoveries ranging from 78.6% to 110.7% with coefficients of variation below 16%. The analysis of blind real-life samples showed a good agreement with results obtained using HPLC-MS/MS. Therefore, the proposed method could be used as an ideal screening surveillance tool for the detection of propiconazole in vegetables.

An Overview for the Nanoparticles-Based Quantitative Lateral Flow Assay

The development of the lateral flow assay (LFA) has received much attention in both academia and industry because of their broad applications to food safety, environmental monitoring, clinical diagnosis, and so forth. The user friendliness, low cost, and easy operation are the most attractive advantages of the LFA. In recent years, quantitative detection has become another focus of LFA development. Here, the most recent studies of quantitative LFAs are reviewed. First, the principles and corresponding formats of quantitative LFAs are introduced. In the biomaterial and nanomaterial sections, the detection, capture, and signal amplification biomolecules and the optical, fluorescent, luminescent, and magnetic labels used in LFAs are described. The invention of dedicated strip readers has drawn further interest in exploiting the better performance of LFAs. Therefore, next, the development of dedicated reader devices is described and the usefulness and specifications of these devices for LFAs are discussed. Finally, the applications of LFAs in the detection of metal ions, biotoxins, pathogenic microorganisms, veterinary drugs, and pesticides in the fields of food safety and environmental health and the detection of nucleic acids, biomarkers, and viruses in clinical analyses are summarized.

Advances in the Determination of Anabolic-Androgenic Steroids: From Standard Practices to Tailor-Designed Multidisciplinary Approaches

Anabolic-androgenic steroids (AASs), a group of compounds frequently misused by athletes and, unfortunately, also by the general population, have lately attracted global attention; thus, significant demands for more precise, facile, and rapid AAS detection have arisen. The standard methods ordinarily used for AAS determination include liquid and gas chromatography coupled with mass spectrometry. However, good knowledge of steroid metabolism, pretreatment of samples (such as derivatization), and well-trained operators of the instruments are required, making this procedure expensive, complicated, and not routinely applicable. In the drive to meet current AAS detection demands, the scientific focus has shifted to developing novel, tailor-made approaches leading to time- and cost-effective, routine, and field-portable methods for AAS determination in various matrices, such as biological fluids, food supplements, meat, water, or other environmental components. Therefore, herein, we present a comprehensive review article covering recent advances in AAS determination, with a strong emphasis on the increasingly important role of chemically designed artificial sensors, biosensors, and antibody- and fluorescence-based methods.

A bifunctional immunosensor based on osmium nano-hydrangeas as a catalytic chromogenic and tinctorial signal output for folic acid detection

As a neglected member of the platinum group elements, osmium, the metal with the highest density in the earth, is very suitable for the preparation of a peroxidase with high catalytic activity and stability, and can also be associated with the development of a sensor. In this study, we accessed Os nano-hydrangeas (OsNHs) with one-pot synthesis and utilized them in a bifunctional immunosensor that can present both catalytic chromogenic and tinctorial signal for nanozyme-linked immunosorbent assay (NLISA) and lateral flow immunoassay (LFIA) for use in folic acid (FA) detection. In the OsNHs-NLISA, the linear range is from 9.42 to 167.53 ng mL^-1. The limit of detection (LOD) is 4.03 ng mL^-1 and the IC₅₀ value is 39.73 ng mL^-1. In OsNHs-LFIA, the visual cut-off value and limit of detection (v-LOD) are 100 ng mL^-1 and 0.01 ng mL^-1, respectively. Additionally, the outcome from the specificity and spiked sample analysis offered recovery from the spiked milk powder sample ranging from 93.9 to 103.6% with a coefficient of variation under 4.9%, compared with UPLC-MS/MS for a correlation of R² = 0.999 and admirable validation. The promising application of the OsNHs can also be used in other bioprobes, and this bifunctional immunosensor analysis mode is suitable for diversified analytes.

Fluorescence polarization immunoassay for rapid determination of dehydroepiandrosterone in human urine

In this paper, five fluorescein-labeled dehydroepiandrosterone (DHEA) derivatives (tracers) with different chain lengths between the fluorescein and hapten were synthesized and featured so as to establish a fluorescence polarization immunoassay (FPIA) for DHEA detection in human urine samples with previously prepared polyclonal antibody against DHEA. The outcomes of the structure of tracer on FPIA sensitivity were investigated. Under the optimal condition, the fluorescence polarization value (FP) decreases linearly in DHEA concentration, ranging from 1.6 to 243.3 ng mL^-1, with the limit of detection of 1.1 ng mL^-1 and IC₅₀ value of 25.1 ng mL^-1. Moreover, the developed FPIA was time-saving as it could complete the detection within 3 min. FPIA and commercial enzyme-linked immunosorbent assay kit were both applied to analyze the spiked human urine samples with DHEA. Excellent recoveries (92.1-108.0%) and satisfactory correlation coefficient (R² = 0.98) were acquired with the two methods, indicating that the developed FPIA was a fast and efficient screening immunoassay with accuracy and sensitivity for DHEA detection in human urine samples. Graphical abstract.

Portable, Rapid, and Sensitive Time-Resolved Fluorescence Immunochromatography for On-Site Detection of Dexamethasone in Milk and Pork

Dexamethasone (DEX) is widely used because of its anti-inflammatory, anti-endotoxin, anti-shock, and stress-enhancing response activities. It can increase the risk of diabetes and hypertension if it is abused or used improperly. However, there is a lack of sensitive and rapid screening methods for DEX in food. In this study, a time-resolved fluorescent microspheres immunochromatographic assay (TRFM-ICA) integrated with a portable fluorescence reader was developed for the quantitative detection of DEX in milk and pork. The cut-off values of the TRFM-ICA were 0.25 ng/mL and 0.7 µg/kg, respectively. The limits of quantitation (LOQs) were 0.003 ng/mL and 0.062 µg/kg, respectively. The recovery rates were 80.0–106.7%, and 78.6–83.6%, respectively, with the coefficients of variation ranging 6.3–12.5%, and 7.5–10.3%, respectively. A parallel experiment for 20 milk and 10 pork samples with LC-MS/MS was carried out to confirm the performance of the on-site application of the developed TRFM-ICA. The results of the two methods are basically the same; the correlation (R²) was >0.98. The establishment of TRFM-ICA will provide a new sensitive and efficient technical support for the rapid screening of DEX in food.

A Pt-Ir nanocube amplified lateral flow immunoassay for dehydroepiandrosterone

The traditional gold-nanoparticle-based lateral flow immunoassay (LFIA) cannot satisfy the requirements for the sensitive detection of dehydroepiandrosterone (DHEA) in human urine. To enhance the sensitivity of the LFIA, platinum-iridium nanocubes (Pt-Ir NCs) with high catalytic efficiency and stability were synthesized and labelled with polyclonal antibody (pAb) to form a pAb-Pt-Ir probe. For the detection of DHEA, a novel LFIA with Pt-Ir NCs as an optical label and an enhanced LFIA in which the peroxidase-like activity of the Pt-Ir NCs was triggered by the introduction of the chromogenic substrate 3-amino-9-ethyl-carbazole (AEC) were developed and compared with a LFIA with platinum nanocubes (PtNCs) as an optical label. The visual limit of detection was 0.5 ng mL-1 for Pt-Ir-LFIA and 0.05 ng mL-1 for AEC-enhanced Pt-Ir-LFIA, in comparison to 100 ng mL-1 for PtNCs-LFIA and 50 ng mL-1 for AEC-enhanced PtNCs-LFIA. The average recoveries from spiked urine samples ranged from 90.8% to 110.4%, with a coefficient of variation below 12.6%, suggesting the accuracy and reliability of our developed immunoassay. Achieving excellent sensitivity, specificity, and reproducibility, Pt-Ir-LFIA provided a promising platform for monitoring DHEA.

Immunoassays for the rapid detection of pantothenic acid in pharmaceutical and food products

Pharmaceutical and food products are fortified with pantothenic acid (PA) to address potential deficiency. Therefore, its fast, reliable, and accurate detection is of great importance to the quality control. Here, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and a gold nanoparticle-based lateral flow immunoassay (LFIA) were established for the determination of PA based on an anti-PA monoclonal antibody (mAb). The ic-ELISA displayed a limit of detection (LOD) of 32.22 ng/mL, and the linear range was 64.44-628.84 ng/mL. Average recoveries of PA in fortified samples were 88.60-110.11% when using the ic-ELISA and a good correlation between the ic-ELISA and LC-MS/MS was obtained when analyzing samples. Furthermore, the developed LFIA strip showed a calculated LOD of 71.99, 115.80, and 240.12 ng/mL in B-complex Vitamin tablets, energy drink and infant milk powder samples, respectively. All the results demonstrated that both of these immunoassays are suitable for determining PA in pharmaceutical and food products.

Interpol review of controlled substances 2016-2019

This review paper covers the forensic-relevant literature in controlled substances from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.