Immunochromatographic assay for the detection of antibiotics in animal-derived foods: A review

Recent Advances of Food Hazard Detection Based on Artificial Nanochannel Sensors

Food quality and safety are related to the health and safety of people, and food hazards are important influencing factors affecting food safety. It is strongly necessary to develop food safety rapid detection technology to ensure food safety. As a new detection technology, artificial nanochannel-based electrochemical and other methods have the advantages of being real-time, simple, and sensitive and are widely used in the detection of food hazards. In this paper, we review artificial nanochannel sensors as a new detection technology in food safety for different types of food hazards: biological hazards (bacteria, toxins, viruses) and chemical hazards (heavy metals, organic pollutants, food additives). At the same time, we critically discuss the advantages and disadvantages of artificial nanochannel sensor detection, as well as the restrictions and solutions of detection, and finally look forward to the challenges and development prospects of food safety detection technology based on the limitations of artificial nanochannel detection. We expect to provide a theoretical basis and inspiration for the development of rapid real-time detection technology for food hazards and the production of portable detection equipment in the future.

Immunoassays and Emerging Analytical Techniques of Fipronil and its Metabolites for Food Safety: A Review

Fipronil, classified as a phenylpyrazole insecticide, is utilized to control agricultural, public health, and veterinary pests. Notably, its unique ecological fate involves degradation to toxic metabolites, which poses the risk of contamination in water and foodstuffs and potential human exposure through the food chain. In response to these concerns, there is a pressing need to develop analytical methodologies for detecting fipronil and its metabolites. This review provides a concise overview of the mode of action, metabolism, and toxicology of fipronil. Additionally, various detection strategies, encompassing antibody-based immunoassays and emerging analytical techniques, such as fluorescence assays based on aptamer/molecularly imprinted polymer/fluorescent probes, electrochemical sensors, and Raman spectroscopy, are thoroughly reviewed and discussed. The focus extends to detecting fipronil and its metabolites in crops, fruits, vegetables, animal-derived foods, water, and bodily fluids. This comprehensive exploration contributes valuable insights into the field, aiming to foster the development and innovation of more sensitive, rapid, and applicable analytical methods.

A highly sensitive hyperbranched Au plasmonic blackbody immunochromatographic assay for detection of leucomalachite green in fish and shrimp

A novel immunochromatographic assay (ICA) based on hyperbranched Au plasmonic blackbodies (AuPBs) with a smartphone readout was fabricated for the detection of leucomalachite green (LMG) in fish and shrimp products. The ICA was carried out in a competitive immunoassay format with AuPBs as labels. The developed AuPBs-ICA allowed for the LMG detection with a low detection limit (0.15 μg L-1) within 5 min by the smartphone reader. With the label-AuPBs ICA, the color intensity response was linearly related to the concentrations of the LMG (0.2 -1.7 μg L-1). The test line signal could be clearly distinguished at a 1.7 μg L-1 LMG as a cut-off level by the naked eye, which is lower than the conventional colloidal gold nanoparticle (2 μg L-1) and star-shaped nanoparticles (1.9 μg L-1) labeling. LMG contamination in samples was determined with the proposed AuPBs-ICA and the enzyme-linked immunosorbent (ELISA). The AuPBs-ICA results showed good agreement with those from the ELISA. The proposed AuPBs-ICA has the potential to be used as a rapid, sensitive, and simple device for the analysis of LMG residues in fish and shrimp samples.

Multiplexed SELEX for Sulfonamide Antibiotics Yielding a Group-Specific DNA Aptamer for Biosensors

The widespread use of sulfonamide (SA) antibiotics in animal husbandry has led to residues of SAs in the environment, causing adverse effects to the ecosystem and a risk of bacterial resistance, which is a potential threat to public health. Therefore, it is highly desirable to develop simple, high-throughput methods that can detect multiple SAs simultaneously. In this study, we isolated aptamers with different specificities based on a multi-SA systematic evolution of ligands by the exponential enrichment (SELEX) strategy using a mixture of sulfadimethoxine (SDM), sulfaquinoxaline (SQX), and sulfamethoxazole (SMZ). Three aptamers were obtained, and one of them showed a similar binding to all tested SAs, with dissociation constant (Kd) ranging from 0.22 to 0.63 μM. For the other two aptamers, one is specific for SQX, and the other is specific for SDM and sulfaclozine. A label-free detection method based on the broad-specificity aptamer was developed for the simultaneous detection of six SAs, with detection of limits ranging from 0.14 to 0.71 μM in a lake water sample. The aptasensor has no binding for other broad-spectrum antibiotics such as β-lactam antibiotics, quinolones, tetracyclines, and chloramphenicol. This work provides a promising biosensor for rapid, multiresidue, and high-throughput detection of SAs, as well as a shortcut for the preparation of different specific recognition elements required for the detection of broad-spectrum antibiotics.

A Sensitive Fluorescence Sensor for Tetracycline Determination Based on Adenine Thymine-Rich Single-Stranded DNA-Templated Copper Nanoclusters

A sensitive fluorescent sensor has been developed for the determination of tetracycline (TC) using adenine thymine (AT)-rich single-stranded DNA (ssDNA) templated copper nanoclusters (CuNCs) as a fluorescent probe. Fluorescent ssDNA-CuNCs were synthesized by employing AT-rich ssDNA as templates and ascorbic acid as reducing agents through a facile one-step method. The as-prepared ssDNA-CuNCs exhibited strong fluorescence with a large Stokes shift (240 nm) and stable fluorescence emission. In the presence of TC, the fluorescent intensity of ssDNA-CuNCs was obviously decreased through the inner filter effect, due to the spectral overlapping between ssDNA-CuNCs and TC. Under the optimal conditions, the strategy exhibited sensitive detection of TC with a linear range from 2 nM to 30 μM and with a limit of detection of 0.5 nM. Furthermore, the sensor was successfully applied for the detection of TC in milk samples. Therefore, it provided a simple, rapid, and label-free fluorescent method for TC detection.

An indirect competitive assay-based method for the sensitive determination of tetracycline residue using a real-time fluorescence-based quantitative polymerase chain reaction

Tetracycline (TC) is an effective antibiotic used to treat humans and livestock, but its inappropriate use imposes toxic effects, including pollution, on environmental ecology and food. Currently, sensitive, accurate, and cost-effective methods that can detect lower concentrations of TC residues in environmental and food samples are needed. In this study, a novel indirect competitive assay-based aptamer method was developed for detecting TC residues through signal amplification by real-time fluorescence-based quantitative polymerase chain reaction. The response surface methodology was introduced to optimize the optimal concentrations (influencing factors) of the three types of single-stranded DNA in the competitive assay process. The optimal conditions for the three types of ssDNA were 112 nM for the specific aptamer of TC (Apt40), 115 nM for the signal DNA, and 83 nM for the DNA catcher. As expected, under optimal conditions, the Ct value was linearly related to the logarithm of TC concentration. The calibration curve equation was Ct = -0.34516 log[TC] + 9.9345 (R2 = 0.998) in the range of 10-3-103 ng mL-1, and the limit of detection was 7.02 × 10-5 ng mL-1. The new method was effectively applied to detect TC residues in wastewater, honey, and milk samples. It achieved an average recovery rate of 101.19% with a small variation of 5.16%. The validation was carried out using an enzyme-linked immunosorbent assay. This approach demonstrates high sensitivity and selectivity, making it well suited for detecting leftover antibiotics in food when using suitable aptamers.

TPN-COF@Fe-MIL-100 composite used as an electrochemical aptasensor for detection of trace tetracycline residues

In this work, a metal-organic framework@covalent organic framework composite (TPN-COF@Fe-MIL-100) was prepared and used as a sensing material to construct an aptasensor for trace detection of tetracycline (TET). The TPN-COF@Fe-MIL-100 integrates a large surface area, porous structure, excellent electrochemical activity, rich chemical functionality, and strong bioaffinity for aptamers, providing abundant active sites to effectively anchor aptamer strands. As a result, the TPN-COF@Fe-MIL-100-based aptasensor shows high sensitivity for detecting TET via specific recognition between aptamer and TET to form G-quadruplex. An ultralow detection limit of 1.227 fg mL-1 is deduced from the electrochemical impedance spectroscopy within a wide linear range of 0.01-10000 pg mL-1 for TET. The TPN-COF@Fe-MIL-100-based aptasensor also exhibits good selectivity, reproducibility, stability, regenerability, and applicability for a real milk sample. Therefore, the TPN-COF@Fe-MIL-100-based aptasensor will be promising for detecting trace harmful antibiotics residues for food safety.

Fluorescent strip sensor for rapid and ultrasensitive determination of fluoroquinolones in fish and milk

The synthetic antibiotics fluoroquinolones are popular due to their good antibacterial performance and low price, but the risk to human health caused by their residues has attracted great attention. In this study, an ultra-sensitive mAb, 4D7, was prepared with an IC₅₀ of 0.027 ng mL^-1 to norfloxacin (NOR) and cross-reactivity of 19.7-47.7% to lomefloxacin (LOM), pefloxacin (PEF), ofloxacin (OFL), enrofloxacin (ENR), ciprofloxacin (CIP), and danofloxacin (DAN). Based on mAb 4D7 and Eu-fluorescent microspheres, a rapid and sensitive immunochromatographic strip was developed for the detection of fluoroquinolone residues in fish and milk. The detection ranges (IC₂₀-IC₈₀) of the strip for the detection of NOR, PEF, LOM, OFL, ENR, CIP and DAN were 0.19-1.1 μg kg^-1, 0.39-2.1 μg kg^-1, 0.5-2.6 μg kg^-1, 0.43-3.3 μg kg^-1, 0.61-3.5 μg kg^-1, 0.69-5.5 μg kg^-1, 0.52-3.4 μg kg^-1 in fish, and 0.027-0.19 μg kg^-1, 0.049-0.34 μg kg^-1, 0.069-0.39 μg kg^-1, 0.06-0.41 μg kg^-1, 0.089-0.65 μg kg^-1, 0.12-0.81 μg kg^-1, 0.091-0.52 μg kg^-1 in milk, respectively. The recovery rates in spiked sample tests were 88.6-113.6% with a coefficient of variation less than 8.4%. Thus the newly-developed strip was sensitive and reliable for rapid on-site detection of fluoroquinolone residues in fish and milk.

High-Efficiency Utilization of Waste Tobacco Stems to Synthesize Novel Biomass-Based Carbon Dots for Precise Detection of Tetracycline Antibiotic Residues

Recycling waste biomass into valuable products (e.g., nanomaterials) is of considerable theoretical and practical significance to achieve future sustainable development. Here, we propose a one-pot hydrothermal synthesis route to convert waste tobacco stems into biomass-based N, S-codoped carbon dots (C-dots) with the assistance of carbon black. Unlike most of the previously reported luminescent C-dots, these biomass-based C-dots showed a satisfactory stability, as well as an excitation-independent fluorescence emission at ~520 nm. Furthermore, they demonstrated a pH-dependent fluorescence emission ability, offering a scaffold to design pH-responsive assays. Moreover, these as-synthesized biomass-based C-dots exhibited a fluorescence response ability toward tetracycline antibiotics (TCs, e.g., TC, CTC, and OTC) through the inner filter effect (IFE), thereby allowing for the establishment a smart analytical platform to sensitively and selectively monitor residual TCs in real environmental water samples. In this study, we explored the conversion of waste tobacco stems into sustainable biomass-based C-dots to develop simple, efficient, label-free, reliable, low-cost, and eco-friendly analytical platforms for environmental pollution traceability analysis, which might provide a novel insight to resolve the ecological and environmental issues derived from waste tobacco stems.

Ultrasensitive Competitive Lateral Flow Immunoassay with Visual Semiquantitative Inspection and Flexible Quantification Capabilities

Antibiotics abuse has caused various problems threatening human health and ecological environment. Monitoring antibiotics residual levels is of great significance, yet still challenging for quantitative point-of-need testing with high-sensitivity and visual capability. Here we developed a competitive lateral flow immunoassay (CLFIA) platform with flexible readout for enrofloxacin (ENR), a regularly added antibiotic. To overcome the limitation of low sensitivity of traditional colloidal gold-based CLFIA, the three-dimensionally assembled gold nanoparticles (AuNPs) within dendritic silica scaffold were fabricated as signal reporters. The assembly structure effectively retained the intrinsic absorption features of hydrophobic AuNPs and greatly enhanced the light extinction ability of a single label for signal amplification. The obtained CLFIA strips can not only achieve qualitative screening of ENR at a very low concentration by naked eye (cutoff value: 0.125 ng/mL), but also enable ultrasensitive quantification of ENR by an optical scanner (limit of detection: 0.00195 ng/mL) or a smartphone (limit of detection: 0.0078 ng/mL). Moreover, to elaborate the visual inspection degree of CLFIA against traditional yes/no interpretation, a novel multirange gradient CLFIA strip was prepared for visually semiquantitative identification of ENR with four concentration ranges. The novel CLFIA platform demonstrated sensitive, specific, and reliable determination of ENR with flexible signal readout and provides a potential and invigorating pathway to point-of-need immunoassay of antibiotics.