Residues In Animal-derived Food Research Articles

Development of a nanobody-horseradish peroxidase fusion-based competitive ELISA to rapidly and sensitively detect Enrofloxacin residues in animal-derived foods

The ability to reliably detect enrofloxacin in animal-derived food products has important health implications. In the present study, a nanobody-horseradish peroxidase fusion specific for ENR was generated to enable a sensitive and rapid competitive ELISA suitable for detecting enrofloxacin in samples of milk and animal tissue. An enrofloxacin hapten generated via the glutaraldehyde method was initially used to immunize an adult Bactrian camel as a means of constructing a phage library. Enrofloxacin−specific nanobodies were then selected through three rounds of biopanning, and HRP-fused versions of these nanobodies were then expressed. Lastly, these nanobodies were used to develop a sensitive cELISA for enrofloxacin detection in milk and animal tissues, with the resultant assay exhibiting an IC50 of 37.41 ng/mL and a linear detection range (IC20-IC80) of 10.89 to 244.34 ng/mL. The limit of detection for this cELISA was 6.48 ng/mL, with 4.66 % cross-reactivity with ciprofloxacin, and recovery rates that ranged from84.99 % to 107.72 % together with an RSD below 10.70 %.

Boronate affinity molecularly imprinted electrochemical sensor based on electrospun carbon nanofibres for selective kanamycin detection

The presence of trace kanamycin (KANA) residues in animal-derived foods from its improper use present a critical public health issue, making the urgent need for the development of sensitive and selective KANA detection methods. In this study, we developed molecularly imprinted polymers (MIPs)-based electrochemical sensor for the detection of KANA, incorporating Co, Mo-doped carbon nanofibres (Co, Mo@CNFs) to modify a glassy carbon electrode (GCE). Then, the MIPs layer was synthesized via electropolymerization using KANA as a template molecule and 3-aminophenylboronic acid (3-APBA) as the functional monomer (as MIPs/Co, Mo@CNFs/GCE), facilitating selective recognition through boric acid affinity. The presence of Co, Mo@CNFs enhanced electron transport across the otherwise insulating MIPs layer, thereby improving the sensor’s selective recognition capabilities. Under optimal conditions, the MIPs/Co, Mo@CNFs/GCE sensor demonstrated precise KANA detection within a concentration range of 1 × 10−2 to 1 × 105 nmol·L−1, achieving a detection limit of 2.56 pmol·L−1. Furthermore, the sensor’s applicability was validated in complex matrices, successfully detecting KANA in serum and milk samples with recovery rates ranging from 95.05 % to 116.43 %. These results confirmed that the proposed sensor is highly effective for detecting KANA in both biological and animal-origin food samples.

A novel HCR-CRISPR/Cas12a immunosensor for the sensitive detection of pesticide residues in animal-derived foods

Pesticides are widely used in the cultivation and breeding of agricultural products. However, pesticide residue monitoring has focused mainly on fruits and vegetables and has not focused on animal-derived foods. Therefore, a novel approach for determining pesticide residues in animal-derived food products via an immunosensor based on a chain hybridization reaction (HCR) with CRISPR/Cas12a is presented. Triazophos pesticide was used as a research object. This method establishes a competitive immunoreaction system in which OVA-hapten is encapsulated on the surface of the enzyme label plate, competing with pesticide molecules bound to antibodies on the surface of the nanogold composite probe. Integrating the immunoreaction with two signal amplification mechanisms, HCR and CRISPR/Cas12a, ensures heightened method sensitivity while maintaining enhanced convenience and speed. The method's detection range spans from 0.01 to 50 ng/mL, with a remarkably low detection limit of 0.013 ng/mL. Moreover, in practical sample applications, the assay exhibited a robust correlation with GC‒MS. This approach uniquely offers real-time, cost-effective, and onsite data, providing a more comprehensive and timely foundation for establishing standards on pesticide residues in animal-derived foods, bolstering food safety surveillance, and upholding public health. Moreover, the proposed HCR-CRISPR/Cas12a immunosensor effectively improved the sensitivity and accuracy of pesticides detection, offering a promising and versatile platform for food safety detection.

A LMOF/MIP paper-based chip and analysis of tetracycline in foodstuff with sample-to-answer performance

The development of high-performance specific sensors is promising for the rapid detection of harmful residues in animal-derived foods. Recently, luminescent metal-organic framework/molecularly imprinted polymer (LMOF/MIP) materials have been developed as ideal candidates for the analysis of harmful residues. Here, we reported a simple fabrication protocol of paper-based chip through in-situ growth of LMOF on a negatively charged modified filter paper, a paper-based molecularly imprinting layer (FP@BA-Eu@MIP) was thereafter successfully prepared via the boronate affinity-based controllable oriented surface imprinting strategy. The paper-based chips obtained were used to construct a rapid test strip of tetracycline (TC). After addition of TC, significant fluorescence changes on the surface of the FP@BA-Eu@MIP paper-based chip could be observed from blue to red via inner filter effect and photo-induced electron transfer under the excitation of 360 nm. The adsorption kinetics was explored in detail. The presented strip exhibited satisfied selectiveness and sensitivity with a limit of detection of 8.47 μg L−1 for TC. It was confirmed that LMOF/MIP as a biomimetic recognition module can play a crucial role in enrichment and fluorescence response. This study provided a real application case for an in-situ fabricated fluorescence paper-based chip in rapidly detecting harmful residues.

Detection and adsorption of florfenicol in milk using bifunctional carbon dot-doped molecularly imprinted polymers.

Detection of florfenicol (FF) residues in animal-derived foods, as one of the most widely used antibiotics, is critically important to food safety. The fluorescent molecularly imprinted polymer (MIP) was synthesized by surface-initiated atom transfer radical polymerization technique with poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres, 4-vinylpyridine, ethylene glycol dimethacrylate, and FF as the matrix, functional monomer, crosslinker, and template molecule, respectively. Meanwhile, N-S co-doped carbon dot (CD) was synthesized with triammonium citrate and thiourea as precursors under microwave irradiation at 400W for 2.5min and then integrated into FF-MIP to obtain CD@FF-MIP. For comparison, non-imprinted polymer (NIP) without FF was also prepared. The adsorption capacity of CD@FF-MIP to FF reached 53.1mgg-1, which was higher than that of FF-MIP (34.7mgg-1), whereas the adsorption capacity of NIP was only 17.3mgg-1. The adsorption equilibrium of three materials was reached within 50min. Particularly, CD@FF-MIP exhibited an excellent fluorescence quenching response to FF in the concentration range of 3-50 µmolL-1. As a result, CD@FF-MIP was successfully utilized to extract FF in milk samples, which were analyzed by high-performance liquid chromatography. The standard recoveries were 95.8%-98.2%, and the relative standard deviation was 1.6%-4.2%. The method showed the advantages of simple operation, high sensitivity, excellent selectivity, and low cost, and also demonstrated a great application prospect in food detection.

Rapid analysis of salbutamol residues in animal-derived food based on the fluorescence of MOFs/MIPs paper-based chips

Mimetic recognition materials for rapid and selective analysis of foodborne contamination from complex foodstuff becomes a hot research topic in the field of food safety. In this work, borate-affinity-functionalized MOF/molecularly imprinted polymer paper-based microfluidic chips (FSU-BA@MIP) were prepared by growing functionalized MOFs on paper surface with 3-carboxyphenylboronic acid (3-CPBA) as the ligands, followed by coating of a MIP layer of salbutamol (SAL) through a borate-affinity surface imprinting strategy. Using the obtained paper-based chip as a mimetic recognition and specific enrichment module, the fluorescence sensing platform achieved visual rapid quantitative analysis of SAL with a linear range of 0.1 × 10−2–5.0 mg L−1. The limits of detection and quantification were calculated to be 0.095 and 0.290 μg kg−1, respectively, and the sample loading via lateral flow aid could be completed within 30 min. The obtained MOFs/MIPs paper chips provide an effective way for the rapid analysis of harmful contaminants from different animal-derived foods.

Enterobacteriaceae Antibiotic Resistance Identification in Slender-billed Gull Species Migrating to Libya

The Libyan coast has various types of wetlands that are passed by many migratory birds throughout the year, however, studies on bacterial isolation from these birds in Lybia are scarce. The present study aimed to isolate enteropathogenic bacterial species from the seagulls that migrated to the Libyan coast as well as identification of the antibiotics that are resistant to these bacteria. A total of 50 fresh fecal samples were collected from slender-billed gulls in January 2023 at Farwa Island near the city of Zuwara, in Western Libya. Bacteria were isolated by conventional culturing method, identified using the Enterosystem 18R, and antibiotic susceptibility tests were conducted on the isolated bacteria. The results revealed the isolation of 46 bacteria, but only 32 of them were identified using biochemical tests. These identified bacteria belong to six species of Enterobacteriacae, namely Citrobacter (C.) freundii, Pantoea (P.) agglomerans, Escherichia (E.) coli, Enterobacter (En.) cloacae, Serratia liquifaciens, and Proteus mirabilis, with percentages of 53.125%, 31.25%, 6.25%, 3.125%, 3.125%, and 3.125%, respectively. All isolated bacteria were 100% sensitive to gentamicin (10 µg) and ciprofloxacin (5 µg). The highest resistance result was observed against the antibiotic cefoxitin (30 µg), with both C. freundii (5 samples) and P. agglomerans (4 samples). Resistance was observed in 5 samples of C. freundii and 4 samples of P. agglomerans out of 11 samples. Resistance to antibiotics, such as azithromycin (15 µg), ceftriaxone (30 µg), and ampicillin (10 µg), was also noted in a few isolates. The results indicated that C. freundii was the most antibiotic-resistant bacterial species isolated in this study. The highest multiple antibiotic resistance index was demonstrated by bacteria C. freundii, P. agglomerans, and En. cloacae, with a value of 0.33 for each of them. In conclusion, slender-billed gulls carry multi-drug-resistant bacteria. The study recommends the implementation of a national program to survey antibiotic-resistant bacteria, determine their prevalence, and assess the presence of antibiotic residues in animal-derived food. Furthermore, the present study advises expanding scientific studies on risk analysis, and antibiotic alternatives in migratory birds.

Determination of 24 Benzimidazoles in meat and meat products by modified QuEChERS coupled with UPLC-MS/MS

In this study, an effective method for the simultaneous determination of 24 Benzimidazoles in meat and meat products based on a modified QuEChERS sample preparation technique coupled with ultra-performance liquid chromatography–tandem mass spectrometry was established. Then, BZDs in meat and meat products were extracted by 0.1 % ammonium hydroxide in acetonitrile, followed by cleanup with 0.1 g C18 and 0.3 g MgSO4, ionized in electrospray positive ionization source mode, and scanned for determination of the precursor ion and product ion by mass spectrometry in multiple reaction monitoring mode. The results showed that 24 BZDs had good linearity in the range of 0.2–100 μg/kg with correlation coefficients >0.999, and the limits of detection ranged from 0.001 to 0.244 µg/kg and the limits of quantification were between 0.002 and 0.738 µg/kg. The average recoveries of BZDs at three different spike levels of 2, 20, and 50 µg/kg were 74.6 % −113.9 %, with intra-day and inter-day relative standard deviations less than 9.86 % and 11.03 %, respectively. This method has been successfully applied to the determination of BZDs in real samples, providing a powerful tool for the monitoring of BZDs residues in animal-derived foods.

A novel photoelectrochemical aptasensor based on 3D flower-like g-C3N4/BiOI p-n heterojunction for the sensitive detection of kanamycin

BackgroundKanamycin (KAN) residues in animal-derived foods continuously enter the human body, which will pose serious threats to human health such as hearing loss, nephrotoxicity and other complications. Therefore, to sensitively detect KAN residues by a reliable technology is extremely urgent in food quality and safety. Compared with traditional methods being limited by cost and complexity, photoelectrochemical (PEC) biosensors benefit from some merits such as rapid response, excellent sensitivity and good stability. In this study, the construction of a highly efficient PEC platform to realize KAN residues detection is discussed. ResultsHerein, a novel p-n heterojunction consisting of flower-like BiOI microspheres and graphite carbon nitride (g-C3N4) nanoflakes was developed to establish a PEC aptasensor for KAN detection at 0 V. The prepared g-C3N4/BiOI heterostructure showed not only significantly enhanced PEC activity due to the larger specific surface area but also greatly increased charge separation efficiency owing to the strong internal electric field. Meanwhile, using g-C3N4/BiOI as a highly efficient photoactive material for binding amine-functionalized aptamers to capture KAN, the photocurrent signals showed a ‘turn off’ mode to achieve the sensitive detection of KAN. The proposed PEC aptasensor exhibited linear response for KAN from 5 × 10−9 to 3 × 10−7 mol L−1 with a low detection limit of 1.31 × 10−9 mol L−1, and satisfactory recoveries (97.44–107.38 %) were obtained in real food samples analysis. SignificanceThis work presented a novel p-n heterojunction-based PEC aptasensor with strong selectivity and stability, rendering it allowed to detect KAN in animal-derived foods including milk, honey and pork. Additionally, the detection range satisfied the MRLs for KAN specified by the national standards, demonstrating the potential application for food analysis. The study provides a new insight into the development of efficient and practical biosensors for antibiotic residues detection.

A ratiometric fluorescent dark box and smartphone integrated portable sensing platform based on hydrogen bonding induction for on-site determination of enrofloxacin

Enrofloxacin (ENR) residues in animal-derived food and water threaten human health. Simple, low-cost and on-site detection methods are urgently needed. Blue emitting carbon quantum dots (CQDs) and orange rhodamine B (RhB) were used as recognition and reference signals, respectively, to construct a ratiometric fluorescence sensor. After the addition of ENR, the color of the sensor changed from orange to blue because hydrogen bonding induced a considerable increase in CQDs fluorescence. Based on this mechanism, a simple and low cost on-site portable sensing platform was constructed, which integrated a stable UV light strip and a smartphone with voice-controlled phototaking function and an RGB app. The t-test results of spiked ENR recoveries for diluted milk, honey and drinking water revealed no significant differences between the ratiometric fluorescent sensor and portable sensing platform. Thus, this portable sensing platform provides a novel strategy for on-site quantification of quinolone antibiotics in foodstuffs and environmental water.

Highly electroactive Co–ZnO/GO nanocomposite: Electrochemical sensing platform for oxytetracycline determination

Antimicrobial residues in animal-derived foods have become a major source of concern around the world. Oxytetracycline (OTC), one of these antibiotics that belongs to the tetracycline family should be detected in these matrices. Nanostructured metal oxides have attracted a lot of scientific attention due to their special characteristics that can be exploited for creating innovative nanodevices. Therefore, in the present study, we report the fabrication of cobalt-doped ZnO/GO nanocomposites for OTC sensors using a simple and environmentally friendly method that does not require toxic solvents. Contact angle measurements, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV–Vis were used to confirm the successful fabrication of the Co–ZnO/GO nanocomposite and to determine the surface area, Structural, morphological features, chemical composition and purity of the nanocomposite. The electrochemical and electrocatalytic properties were recorded using cyclic voltammetry (CV), electrochemical impedance spectroscopy, and differential pulse voltammetry (DPV). Optimizing parameters such as scan rate, pH value, deposition time, and deposition potential, we achieve a wide linear concentration range from 10−12 M to 10−7 M, with an impressive detection limit of 1.6 10−13 M.Notably, our sensor exhibits remarkable selectivity, demonstrating its usefulness for the detection of oxytetracycline traces in real milk samples. These results emphasize the novelty and practical significance of our work and provide a promising avenue for the development of sensitive and selective electrochemical sensing platforms in various fields.

Fragmentation characteristics-based nontargeted screening method of exogenous chemical residues in animal-derived foods using reversed-phase and hydrophilic interaction liquid chromatography–high-resolution mass spectrometry

Fragmentation characteristics are crucial for nontargeted screening to discover and identify unknown exogenous chemical residues in animal-derived foods. In this study, first, fragmentation characteristics of 51 classes of exogenous chemical residues were summarized based on experimental mass spectra of standards in reversed-phase and hydrophilic interaction liquid chromatography–high-resolution mass spectrometry (MS) and mass spectra from the MassBank of North America (MoNA) library. According to the proportion of fragmentation characteristics to the total number of chemical residues in each class, four screening levels were defined to classify 51 classes of chemical residues. Then, a nontargeted screening method was developed based on the fragmentation characteristics. The evaluation results of 82 standards indicated that more than 90 % of the chemical residues with MS/MS spectra can be identified at concentrations of 100 and 500 μg/kg, and about 80 % can be identified at 10 μg/kg. Finally, the nontargeted screening method was applied to 16 meat samples and 21 egg samples as examples. As a result, eight chemical residues and transformation products (TPs) of 5 classes in the exemplary samples were found and identified, in which 3 TPs of azithromycin were identified by fragmentation characteristics-assisted structure interpretation. The results demonstrated the practicability of the nontargeted screening method for routine risk screening of food safety.

Quantum dot-based fluorescence-linked immunosorbent assay for the rapid detection of lomefloxacin in animal-derived foods

Lomefloxacin (LMF), a third-generation fluoroquinolone antibacterial agent, is often used to treat bacterial and mycoplasma infections. However, due to its prolonged half-life and slow metabolism, it is prone to residues in animal-derived foods, posing a potential food safety risk. Therefore, it is particularly urgent and important to establish a method for detecting lomefloxacin. In this study, direct and indirect competitive fluorescence-linked immunosorbent assay (dc-FLISA and ic-FLISA) based on quantum dots (QDs) was established for the detection of LMF. As for dc-FLISA, the half-maximal inhibitory concentration (IC50) and limit of detection (LOD) were 0.84 ng/mL, 0.04 ng/mL, respectively, the detection ranges from 0.08 to 9.11 ng/mL. The IC50 and LOD of ic-FLISA were 0.43 ng/mL and 0.03 ng/mL, respectively, meanwhile the detection ranges from 0.05 to 3.49 ng/mL. The recoveries of dc-FLISA and ic-FLISA in animal-derived foods (milk, fish, chicken, and honey), ranged from 95.8% to 105.2% and from 96.3% to 103.4%, respectively, with the coefficients of variation less than 8%. These results suggest that the dc-FLISA and ic-FLISA methods, which are based on QD labelling, are highly sensitive and cost-effective, and can be effectively used to detect LMF in animal-derived foods.

Isothermal Reciprocal Catalytic DNA Circuit for Sensitive Analysis of Kanamycin.

Inappropriate use of veterinary drugs can result in the presence of antibiotic residues in animal-derived foods, which is a threat to human health. A simple yet efficient antibiotic-sensing method is highly desirable. Programmable DNA amplification circuits have supplemented robust toolkits for food contaminants monitoring. However, they currently face limitations in terms of their intricate design and low signal gain. Herein, we have engineered a robust reciprocal catalytic DNA (RCD) circuit for highly efficient bioanalysis. The trigger initiates the cascade hybridization reaction (CHR) to yield plenty of repeated initiators for activating the rolling circle amplification (RCA) circuit. Then the RCA-generated numerous reconstituted triggers can reversely stimulate the CHR circuit. This results in a self-sufficient supply of numerous initiators and triggers for the successive cross-invasion of CHR and RCA amplifiers, thus leading to exponential signal amplification for the highly efficient detection of analytes. With its flexible programmability and modular features, the RCD amplifier can serve as a universal toolbox for the high-performance and accurate sensing of kanamycin in buffer and food samples including milk, honey, and fish, highlighting its enormous promise for low-abundance contaminant analysis in foodstuffs.

Determination of 60 Food-Borne Stimulant Drug Residues in Animal-Derived Foods by Solid-Phase Extraction Purification and Ultra-High-Performance Liquid Chromatography-Quadrupole/Orbitrap High-Resolution Mass Spectrometry

A method for the rapid screening and confirmation of 60 food-borne stimulants in animal-derived foods was developed using the ultra-high-performance liquid chromatography-quadrupole/orbitrap high-resolution mass spectrometry (UPLC-Q/Orbitrap HRMS). After enzymatic hydrolysis at 37°C for 16 h, the samples were extracted with acetonitrile solution. The extraction solution was purified by PRiME HLB pass-through solid-phase extraction cartridge and redissolved by nitrogen blowing. The target compounds of reconstitution fluid were separated by Hypersil GOLD™ VANQUISH column (2.1 mm × 100 mm, 1.9 μm). The raw data were collected for the target compounds in Full Scan-ddMS2 mode, and then the Quan Browser module under Xcalibur software can be used to analyze the quantitative results of the samples. The combination of Tracefinder and mzVault software can realize the qualitative screening and confirmation of the samples. The results showed that the relative deviation of the exact mass of the 60 food-borne stimulants was less than 5.0 × 10−6, which had a good linear relationship in the corresponding concentration, and the correlation coefficient (R2) was greater than 0.9966. The detection limit ranged from 0.05 to 0.5 μg/kg. The quantification limit ranged from 0.1 to 1 μg/kg. The method recoveries ranged from 70.2% to 111.9% with relative standard deviations of 0.05% to 9.00% (n = 6). The method is easy to operate, covers a wide range of targets, and has high efficiency and accuracy. It is suitable for rapid screening and confirmation of various food-derived stimulants in animal-derived foods and provides assistance for food safety in the major events.

Antibody Production, Immunoassay Establishment, and Specificity Study for Flunixin and 5-Hydroxyflunixin.

Flunixin (FLU) is a nonsteroidal drug that is widely used in animals, causing severe drug residues in animal-derived foods and environment. The development of antibody-based rapid immunoassay methods is of great significance for the monitoring of FLU and its metabolite 5-hydroxyflunixin (5-FLU). We prepared monoclonal antibodies (mAbs) with different recognition spectra through FLU-keyhole limpet hemocyanin conjugates as immunogen coupled with antibody screening strategies. mAb5E6 and mAb6D7 recognized FLU with high affinity, and mAb2H5 and mAb4A4 recognized FLU and 5-FLU with broad specificity. Through evaluating the recognition of these mAbs against more than 11 structural analogues and employing computational chemistry, molecular docking, and molecular dynamics methodologies, we preliminarily determined the recognition epitope and recognition mechanism of these mAbs. Finally, an indirect competitive enzyme-linked immunosorbent assay for FLU based on mAb6D7 was developed, which exhibited limits of detection as low as 0.016-0.042 μg kg -1 (L-1) in milk and muscle samples.

Smartphone-based pH responsive 3-channel colorimetric biosensor for non-enzymatic multi-antibiotic residues.

Antibiotic residues in animal-derived food pose a risk to food safety and human health. Here, a smartphone-based pH-responsive 3-channel colorimetric biosensor is constructed for rapid detection of non-enzymatic multi-antibiotic residues in milk. In this system, a magnetic separation and enrichment approach is designed to specifically capture different antibiotic residues in complex environment. Indicators loaded on polydopamine-silver nanoparticles with excellently pH responsive visualization properties are utilized to ensure the high sensitivity of detection system. Moreover, smartphones are introduced to fulfill the demand for portable and on-site inspection of practical applications. It achieves simultaneous detection of oxytetracycline, kanamycin and streptomycin in the linear range of 1-105 pg/mL with detection limits of 0.085, 0.168, and 0.307pg/mL, respectively. The practicality of the reported multi-antibiotic residues detection system is successfully demonstrated and evaluated challenging milk samples. Therefore, this system demonstrates the wide applications in multi-antibiotic residue analysis and food safety guarantee.

Determination of niclosamide and its two metabolites in fish by molecularly imprinted microsphere-based pseudo-ELISA

Niclosamide is usually used for the treatment of parasite infections in animals. However, niclosamide and one of its metabolites 2-chloro-4-nitroaniline are mutagenic substances, and their residues in animal-derived foods are potential risks to consumers. As far as we know, there has been no immunoassay or pseudo immunoassay reported to determine niclosamide and its metabolites in animal-derived foods. In this study, a molecularly imprinted microsphere for niclosamide was first synthesized, and a streptavidin-horseradish peroxidase labelled conjugate was also synthesized. The two reagents were used to develop a pseudo enzyme-linked immunosorbent assay on conventional microplates for the determination of niclosamide and its two metabolites (2-chloro-4-nitroaniline and 5-chlorosalicylic acid) in fish. Because biotinylated horseradish peroxidase was used to amplify the signal, the method sensitivities for the three analytes were increased fivefold to 27.5-fold (limits of detection of 0.004–0.03 ng/mL) in comparison with the use of single horseradish peroxidase labelled conjugate (limits of detection of 0.11–0.16 ng/mL). Their recoveries from the standards fortified blank fish samples were in the range of 70.6–95.5%. This is the first study reporting a molecularly imprinted polymer-based pseudo immunoassay for screening of niclosamide and its metabolites in food sample.

Development of a receptor based signal amplified fluorescence polarization assay for multi-detection of 35 sulfonamides in pork.

With the increasing focus on food security, a screening method with high-throughput, ultra-sensitivity, and user-friendly operation is urgently needed for monitoring of sulfonamides residues in animal-derived foods. In this study, the sulfonamides' receptor dihydropteroate synthase of Staphylococcus aureus was subjected to saturate mutation, and a mutant with higher affinities for sulfonamides was obtained. The mutant was then used as recognition material to establish a fluorescence polarization assay for determination of 35 sulfonamides in pork. Due to the use of an enhanced fluorescent tracer containing two fluorophore molecules, the sensitivities for the 35 sulfonamides were improved for 2.8-8.6 folds (LODs 0.03-1.16ng/mL) in comparison with using conventional fluorescent tracer.The present method outperformed all previous fluorescence polarization (immuno)assays for sulfonamides due to its broader spectrum, higher sensitivity, and shorter assay time. Furthermore, this is the first study reporting an enhanced fluorescence polarization assay for determination of small molecule substance.

Simultaneous quantitative determination of residues of abamectin, ivermectin, albendazole and its three metabolites in beef and chicken by HPLC-PDA.

Antimicrobial drugs are frequently used in a combination or shuttle way to cope with coinfection of bacteria or parasites and prevent drug resistance, thus the accurate quantification of multiple drug residues in animal-derived foods is crucial to ensure food safety. Here, a simple and efficient high-performance liquid chromatography-photodiode array (HPLC-PDA) method was established for the simultaneous quantitative screening of six common residues of antiparasitic drugs, including abamectin (ABM), ivermectin (IVM), albendazole (ABZ) and the three metabolites of ABZ in beef and chicken. The LODs and LOQs for six target compounds in beef and chicken are determined to be 3.2 to 12.5µg/kg and 9.0 to 30.0µg/kg, respectively. The calibration curves show good linearity (R2≥0.9990) between the peak area and concentration. The recoveries from the fortified blank samples are all above 85.10%. Finally, the applicability of the HPLC-PDA method is successfully demonstrated by the real sample analysis.