Validation of HPLC Multi-residue Method for Determination of Fluoroquinolones, Tetracycline, Sulphonamides and Chloramphenicol Residues in Bovine Milk

Highly sensitive antibiotic sensing based on optical weak value amplification: A case study of chloramphenicol

The public health concern of antibiotic residues in animal-origin food has been a long-standing issue. In this work, we present a novel method for antibiotic detection, leveraging optical weak value amplification and harnessing an indirect competitive inhibition assay, which significantly boosts the system's sensitivity in identifying small molecule antibiotics. We chose chloramphenicol as a model compound and mixed it with chloramphenicol-bovine serum albumin conjugates to bind to the chloramphenicol antibody competitively. We achieved a broad linear detection range of up to 3.24 ng/mL and a high concentration resolution of 33.20 pg/mL. To further validate the universality of our proposed detection methodology, we successfully applied it to testing gibberellin and tetracycline. Moreover, we conducted regeneration experiments and real-sample correlation studies. This study introduces a novel strategy for the label-free optical sensing of small molecule antibiotics, greatly expanding the range of applications for sensors utilizing optical weak value amplification.

Development, synthesis, and application of magnetic layered double hydroxides (Fe3O4@SiO-LDH/DS-) as an efficient adsorbent for the removal of tetracyclines from milk samples

This work presents the development, synthesis, and application of a layered double hydroxide (LDH) coupled to magnetic particles for the removal of antibiotics as tetracyclines (TC´s): tetracycline (TC), chlortetracycline (CT), oxytetracycline (OT), and doxycycline (DT) from milk samples. The LDH synthesis conditions, reaction time (30-90 min), molar ratios Mg2+/Al3+ (7:1-1:7), interlayer anion (NO3-, Cl-, CO32-, and dodecyl sulphate (DS-)) were evaluated. Under synthesis conditions (reaction time of 30 min, Mg2+/Al3+ molar ratio of 7:1, and DS- as interlayer anion), the LDH was coupled in a magnetic solid phase microextraction (MSPμE) methodology. At the optimal extraction conditions (pH 6, 5 min of contact time, 10 mg of adsorbent), a removal percentage of 99.0 % was obtained for each tetracycline. FTIR, TGA, SEM, and adsorption isotherms were employed to characterize the optimal adsorbent. Each experiment was corroborated by large-volume sample stacking capillary electrophoresis (LVSS-CE). The adsorbent was applied directly to positive milk samples (previously tested) for TC´s removal.

Development of an angle-adjustable photonic crystal fluorescence platform for sensitive detection of oxytetracycline

We pioneered an angle-adjustable photonic crystal fluorescence platform (APC-Fluor) that integrates PCs, an angular resolution spectrometer and a strategically aligned laser source. This configuration, featuring a coaxial rotating swing arm, allows for precise control over the angles of incidence and emission. The presence of photonic crystal microcavities facilitates the dispersion of fluorescent materials and promotes the transition of electrons from the excited state to the lowest vibrational energy level. The optical resonance effect triggered by modulating the alignment of the reflection peaks of the photonic crystals with the emission peaks of the fluorescent materials can significantly enhance the fluorescence intensity. Compared with the single BSA-AuNCs, the optimized fluorescence intensity can be significantly increased by 11.9-fold. The APC-Fluor system showcases rapid and highly sensitive detection capabilities for oxytetracycline (OTC), exhibiting a response across a concentration range from 2 to 1 × 104 nM and achieving a notably low detection limit of 1.03 nM.

Four Kinds of Polymer Microspheres Prepared by the Seed Swelling Method Used to Purify the Industrial Production of Phytol

Four monodisperse porous polymer microspheres were successfully prepared by seed emulsion polymerization and used as stationary phases for HPLC and preparative high-performance liquid chromatography (Prep-HPLC). All four polymer microspheres(polystyrene-polystyrene (PS-PS), polystyrene-poly(glycidyl methylate) (PS-PGMA), polystyrene-poly(methyl methylate) and poly(glycidyl methylate)-poly(glycidyl methylate) were used for filling HPLC empty columns. According to the analysis results of the HPLC column, PS-PS and PS-PGMA microspheres were screened out as the stationary phase of Prep-HPLC. The industrial-grade phytol was successfully separated and purified, and the purity of the final phytol was as high as 99%. The two types of polymer microspheres have been applied to industrial-grade phytol purification and have been used in factories.

High-sensitively fluorescent switch-type sensing for Ag+ and halide anions of 2D Cd-based network constructed with logic gates

Effective detection of the concentration of Ag+ ions in bactericidal fluid is one of the necessary conditions for their effective utilization for sterilization. A novel 2D Cd(II) coordination polymer (CP1), named as [Cd(HDPN)(4,4'-bbpy)]·2H2O, was hydrothermally synthesized using 5-(2',4'-dicarboxylphenyl) nicotic acid (H3DPN) and 4,4'-bis(imidazolyl)biphenyl (4,4'-bbpy). The structure analysis discovered that CP1 possessed a 2D network structure of dinuclear inorganic building blocks. Fluorescence sensing discovered that CP1 could high-sensitively detect Ag+, tetracycline, nitrobenzene and pyrimethanil and the lowest limit of detection (LOD) were 1.44 × 10-8M, 2.15 × 10-8M, 8.09 × 10-8M, and 2.54 × 10-7M, respectively. It is worth noting that the quenching occurs after the addition of Ag+ to the aqueous solution of CP1, and then it gradually recovers when one of the halide anions (X- = Cl-, Br- and I-) is added, forming a unique "on-off-on" fluorescence sensor for Ag+ and constructing a simple logic gate. The fluorescence sensing mechanism of CP1 was investigated using ultraviolet-visible spectroscopy, PXRD, XPS, and DFT methods. The research indicates that CP1 is anticipated to serve as an excellent multifunctional fluorescence sensor, especially as a switch-type sensor for Ag+ and the halide anions.

Aptamer-modified paper-based analytical devices for the detection of food hazards: Emerging applications and future perspective

Food analysis plays a critical role in assessing human health risks and monitoring food quality and safety. Currently, there is a pressing need for a reliable, portable, and quick recognition element for point-of-care testing (POCT) to better serve the demands of on-site food analysis. Aptamer-modified paper-based analytical devices (Apt-PADs) have excellent characteristics of high portability, high sensitivity, high specificity, and on-site detection, which have been widely used and concerned in the field of food safety. The article reviews the basic components and working principles of Apt-PADs, and introduces their representative applications detecting food hazards. Finally, the advantages, challenges, and future directions of Apt-PADs-based sensing performance are discussed, to provide new directions and insights for researchers to select appropriate Apt-PADs according to specific applications.

Status of antibiotic residues in milk and dairy products of Iran: a systematic review and meta-analysis

Background

Today, antibiotics are widely used for treatment and feed additives to enhance livestock growth. Antibiotic residues may be found in food of animal origin for various reasons, including ignoring the withdrawal period after treatment, overuse for animals, and contamination of feed with treated animals in animal products. Among animal products, dairy products have a special place in the human diet, and antibiotic residues in them have caused a great deal of concern among consumers.

Objective

This systematic review and meta-analysis aimed to evaluate and compare studies conducted in Iran on antibiotic residues in dairy products during 2000-2022.

Methods

In this review, 52 eligible studies were collected by searching the Scientific Information Database (SID), Magiran, Google Scholar, Science-Direct, Scopus, and PubMed using the English or Persian keywords such as an antibiotic or antimicrobial residue, Beta-lactam residue, Tetracycline residue, Sulfonamide residue, Chloramphenicol residue, Aminoglycosides residue, Macrolide residue, Quinolones residue, Milk, Raw milk, Pasteurized milk, UHT milk, Powder milk, Cheese, Yogurt, Butter, Cream, Doogh, Kashk, Ice cream, and Iran.

Results

According to the reviewed studies, the total prevalence of antibiotic residues in dairy products was 29% (95% CI: 15-43%). Among the seven evaluated antibiotic groups, most studies have been conducted on tetracycline, beta-lactam, and sulfonamide groups, with 16, 10, and 7 respectively, and the highest level of contamination with 663 ± 1540 μg/l is related to tetracycline. Most studies on antibiotic dairy product residues in Iran with 12, 11, and 8 studies are associated with East Azarbaijan province, then Tehran and Khorasan Razavi respectively, and no study has been conducted in 11 provinces of the country. According to the studies, Gilan, Qazvin and Razavi Khorasan provinces had the highest amount of antibiotic residue in milk with an average value of 56.415 ± 33.354, 45.955 ± 4.179 and 45.928 ± 33.027, respectively. Most of the methods used in the studies to measure antibiotic residues in milk were the Copan test kit and the HPLC method, which were used in 19 and 14 studies, respectively.

Conclusions

Studies have shown that the prevalence of antibiotic residue in dairy products in Iran is high, so applying an effective strategy and developing the necessary standards in this field to control milk quality is a public health necessity. The findings of this study show that further evaluation of fermented dairy products, especially non-fermented ones such as butter and cream, is needed to prevent adverse health reactions.

Sensitive fluorescence assay of chloramphenicol coupled with two-level isothermal amplification using a self-powered catalyzed hairpin assembly and entropy-driven circuit

Two levels of nucleic acids-based isothermal amplification normally require a long reaction time due to the low concentration of catalyst, which limits its practical application. A sensitive fluorescence assay of chloramphenicol (CAP) was developed coupled with two-level isothermal amplification using a self-powered catalyzed hairpin assembly (CHA) and entropy-driven circuit (EDC). CAP can bind with its aptamer to open its closed structure. The opened hairpin can initiate self-powered CHA and EDC. The product of CHA can circularly catalyze the CHA with increasing concentration. In principle, the product of CHA plays the role of catalyst and increases with the progression of the reaction. Compared with the normal two levels of amplification, the amplification efficiency of our strategy is much higher due to the self-powered reaction by the CHA product. Thus, the reaction time is shortened to 110 min in this strategy. Moreover, the detection limit for CAP can achieve 0.1 pM and shows promising prospects for practical application.

A facile fabric phase sorptive extraction method for monitoring chloramphenicol residues in milk samples

Determination of pharmaceutical active molecules in the biological matrices is crucial in various fields of clinical and pharmaceutical chemistry, e.g., in pharmacokinetic studies, developing new drugs, or therapeutic drug monitoring. Chloramphenicol (CP) is used for treating bacterial infections, and it's one of the first antibiotics synthetically manufactured on a large scale. Fabric phase sorptive extraction (FPSE) was used to determine Chloramphenicol antibiotic residues in milk samples by means of validated HPLC-DAD instrumentation. Cellulose fabric phases modified with polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol triblock copolymer was synthesized using sol-gel synthesis approach (Sol-gel PEG-PPG-PEG) and used for batch-type fabric phase extractions. Experimental variables of the FPSE method for antibiotic molecules were investigated and optimized systematically. The HPLC analysis of chloramphenicol was performed using a C18 column, isocratic elution of trifluoroacetic acid (0.1%), methanol, and acetonitrile (17:53:30) with a flow rate of 1.0 mL/min. The linear range for the proposed method for chloramphenicol (r2 > 0.9982) was obtained in the range of 25.0-1000.0 ng/mL. The limit of detections (LOD) is 8.3 ng/mL, while RSDs% are below 4.1%. Finally, the developed method based on FPSE-HPLC-DAD was applied to milk samples to quantitatively determine antibiotic residues.

Two birds with one stone: A universal design and application of signal-on labeled fluorescent/electrochemical dual-signal mode biosensor for the detection of tetracycline residues in tap water, milk and chicken

An ingenious and universal design of fluorescent/electrochemical dual-signal mode sensing platform was constructed for the sensitive, selective and accurate detection of tetracycline (TET). Apt-functionalized nano-magnetic beads (Fe3O4-Apt) as capture probe, Apt-complementary short-chain functionalized fluorescent MOF loaded with methylene blue (MB) (cDNA-MOF-MB) as dual-signal tag were prepared. The sensing platform (Fe3O4-Apt/cDNA-MOF-MB) was formed based on the base complementary pairing of Apt and cDNA. With the help of Apt for target recognition, together with magnetic separation technology, a dual-signal mode biosensor was constructed. The dual-signal mode biosensor exhibited a wide linear concentration range from 1.00 × 10-9 g/mL to 1.00 × 10-4 g/mL with a low limit of detection (LOD) of 1.69 × 10-10 g/mL (fluorescence mode assay) and 1.15 × 10-10 g/mL (electrochemical mode assay). The proposed biosensor had been successfully applied to the determination of TET content in real samples with satisfactory recoveries (94.99-101.30%).

On-site detection of chloramphenicol in fish using SERS-based magnetic aptasensor coupled with a handheld Raman spectrometer

In recent years, the rapid detection of chloramphenicol (CAP) has become a market demand due to its high toxicity. In this study, for the first time, a portable surface-enhanced Raman scattering (SERS) aptasensor for the rapid and on-site detection of chloramphenicol (CAP) residues in fish was developed. Fe3O4@Au nanoflowers combined with sulfhydryl (SH)-CAP aptamer complementary DNA acted as capture probes. SH-CAP aptamer modified Au@Ag nanoparticles (Au@Ag NPs) embedded with 4-mercaptobenzoic acid (4-MBA) were served as reporter probes. The strongest Raman intensity was produced due to the coupling of Fe3O4@Au nanoflowers (Fe3O4@Au NFs) and Au@Ag NPs. For CAP detection, a wide linear range from 0.001 to 1000 μg/L, with an R2 of 0.9805, was obtained. The limit of detection was determined to be 0.87 ng/L. The SERS aptasensor showed excellent performance for analytical applications for real fish samples. Compared with the conventional HPLC method, the developed SERS aptasensor coupled with a handheld Raman spectrometer had flexible application and avoided the limitations of complex operating conditions. It should be a promising portable analytical tool for analysis of drug residues in the field.

Lateral Flow Immunoassay Based on Quantum-Dot Nanobeads for Detection of Chloramphenicol in Aquatic Products

Quantum dot nanobeads (QBs) were used as signal source to develop competitive lateral flow immunoassay (LFIA) for the detection of chloramphenicol (CAP). The quantitative detection of CAP was achieved by calculating the total color difference (∆E) values of the test line (T line) using the images of test strips. QB-based LFIA (QBs-LFIA) allowed the effective dynamic linear detection of CAP in the range of 0.1-1.5 ng/mL. The limit of detection (LOD) was 3.0 ng/mL, which was 50 and 667 times lower than those achieved for two different brands of colloidal gold kits. The recoveries of CAP during real-sample detection were 82.82-104.91% at spiked levels of 0.1, 0.7, and 1.5 ng/mL. These results indicate that the developed QBs-LFIA facilitates the sensitive detection of CAP.

Electrospun nanofiber-based indicatorpaper sensing platform for fluorescence and visualization detection of norfloxacin

Norfloxacin (NOR) residues in water pose a serious threat to human health via the food chain, necessitating the development of a rapid on-site antibiotic detection technique. In this work, we utilize electrostatic spinning technology that combines polyacrylonitrile (PAN) fibers and adenosine triphosphate (ATP)-rare earth metal Tb3+ complexes (ATP/Tb) to construct a new ternary film-based sensor for sensitive, quick, and convenient field testing of NOR in water. The operating mechanism is that the ternary system produces gradually enhanced bright green fluorescence at increasing concentrations of NOR. The unique fluorescence property of the ternary systems is attributed to the use of ATP, rather than the commonly used adenosine monophosphate (AMP), to coordinate with Tb3+, which avoided the possible fluorescence quenching from competitive water binding. Benefiting from the PAN nanofiber's superior stability, acid, and alkali resistance, and flexibility as support, the ternary system exhibited a good linear response to NOR in a wide dynamic range of 0.04-30 μM at the detection limit of 16 nM. Additionally, the combination of a smartphone color recognition app allows for quick on-scene NOR detection. This film sensing strategy is instructive for the development of smart and portable sensing platforms for real-time detection of analytes such as antibiotics, pesticide residues, and hazardous materials in water bodies.

Carbon-Based Electrochemical (Bio)sensors for the Detection of Carbendazim: A Review

Carbendazim, a fungicide widely used in agriculture, has been classified as a hazardous chemical by the World Health Organization due to its environmental persistence. It is prohibited in several countries; therefore, detecting it in food and environmental samples is highly necessary. A reliable, rapid, and low-cost method uses electrochemical sensors and biosensors, especially those modified with carbon-based materials with good analytical performance. In this review, we summarize the use of carbon-based electrochemical (bio)sensors for detecting carbendazim in environmental and food matrixes, with a particular interest in the role of carbon materials. Focus on publications between 2018 and 2023 that have been describing the use of carbon nanotubes, carbon nitride, graphene, and its derivatives, and carbon-based materials as modifiers, emphasizing the analytical performance obtained, such as linear range, detection limit, selectivity, and the matrix where the detection was applied.

Flexible SERS sensor using AuNTs-assembled PDMS film coupled chemometric algorithms for rapid detection of chloramphenicol in food

The misuse of chloramphenicol (CAP) has led to the development of drug-resistant strains that pose significant threats to public health. Here, we propose a universal flexible surface-enhanced Raman spectroscopy (SERS) sensor utilizing gold nanotriangles (AuNTs) and polydimethylsiloxane (PDMS) film for rapid detection of CAP in food samples. Initially, AuNTs@PDMS with unique optical and plasmonic properties were used to collect spectra of CAP. Afterward, four chemometric algorithms were executed and compared. Accordingly, random frog-partial least squares (RF-PLS) exhibited optimum results with correlation coefficient of prediction (Rp = 0.9802) and the lowest root-mean-square error of prediction (RMSEP = 0.348 µg/mL). Furthermore, the sensor's efficacy to detect CAP in milk samples was confirmed, and the findings were compatible with the conventional HPLC approach (P > 0.05). Therefore, the proposed flexible SERS sensor could effectively be used to monitor milk quality and safety.

Rational Truncation of Aptamer for Ultrasensitive Aptasensing of Chloramphenicol: Studies Using Bio-Layer Interferometry

Aptamers are an excellent choice for the selective detection of small molecules. However, the previously reported aptamer for chloramphenicol suffers from low affinity, probably as a result of steric hindrance due to its bulky nature (80 nucleotides) leading to lower sensitivity in analytical assays. The present work was aimed at improving this binding affinity by truncating the aptamer without compromising its stability and three-dimensional folding. Shorter aptamer sequences were designed by systematically removing bases from each or both ends of the original aptamer. Thermodynamic factors were evaluated computationally to provide insight into the stability and folding patterns of the modified aptamers. Binding affinities were evaluated using bio-layer interferometry. Among the eleven sequences generated, one aptamer was selected based on its low dissociation constant, length, and regression of model fitting with association and dissociation curves. The dissociation constant could be lowered by 86.93% by truncating 30 bases from the 3' end of the previously reported aptamer. The selected aptamer was used for the detection of chloramphenicol in honey samples, based on a visible color change upon the aggregation of gold nanospheres caused by aptamer desorption. The detection limit could be reduced 32.87 times (1.673 pg mL^-1) using the modified length aptamer, indicating its improved affinity as well as its suitability in real-sample analysis for the ultrasensitive detection of chloramphenicol.

Development and Validation of Aptasensor Based on MnO2 for the Detection of Sulfadiazine Residues

The monitoring of sulfadiazine (SDZ) is of great significance for food safety, environmental protection, and human health. In this study, a fluorescent aptasensor based on MnO₂ and FAM-labeled SDZ aptamer (FAM-SDZ30-1) was developed for the sensitive and selective detection of SDZ in food and environmental samples. MnO₂ nanosheets adsorbed rapidly to the aptamer through its electrostatic interaction with the base, providing the basis for an ultrasensitive SDZ detection. Molecular dynamics was used to explain the combination of SMZ1S and SMZ. This fluorescent aptasensor exhibited high sensitivity and selectivity with a limit of detection of 3.25 ng/mL and a linear range of 5-40 ng/mL. The recoveries ranged from 87.19% to 109.26% and the coefficients of variation ranged from 3.13% to 13.14%. In addition, the results of the aptasensor showed an excellent correlation with high-performance liquid chromatography (HPLC). Therefore, this aptasensor based on MnO₂ is a potentially useful methodology for highly sensitive and selective detection of SDZ in foods and environments.

Intelligent visual detection of OTC enabled by a multicolor fluorescence nanoprobe: Europium complex functionalized carbon dots

It is of great significance to realize ultra-sensitive and visual detection of oxytetracycline (OTC) residues, especially for public health and environmental safety. In this study, a multicolor fluorescence sensing platform (CDs-Cit-Eu) for OTC detection was constructed by using rare earth europium complex functionalized carbon dots (CDs). The blue-emitting CDs (λ_em = 450 nm) prepared by one-step hydrothermal method using nannochloropsis were not only the scaffold of Eu³⁺ ion coordination, but also the recognition unit of OTC. After adding OTC to the multicolor fluorescent sensor, the emission intensity of CDs decreased slowly, and the emission intensity of Eu³⁺ ions (λ_em = 617 nm) enhanced significantly, accompanying by a significant color change of the nanoprobe from blue to red. The detection limit of the probe for OTC was calculated to be 3.5 nM, manifesting ultra-high sensitivity towards OTC detection. In addition, OTC detection in real samples (honey, lake water, tap water) was successfully achieved. Moreover, a semi-hydrophobic luminescent film SA/PVA/CDs-Cit-Eu was also prepared for OTC detection. With the help of smartphone color recognition APP, real-time intelligent detection of OTC was realized.

Electrochemical aptasensor based on gold nanoparticle decorated Ti3C2Tx nanocomposites for chloramphenicol detection

Using gold (Au) nanoparticle decorated Ti₃C₂T_x (Ti₃C₂T_x-Au) nanocomposites, a highly sensitive electrochemical aptasensor for the effective detection of chloramphenicol has been developed. As a two-dimensional layered material, the prepared composite not only provides high surface area, good conductivity, and thermal stability but also substantial binding sites for aptamers with high sensitivity and selectivity for the accurate determination of chloramphenicol. Interestingly, the conductivity and active sites were enhanced by freeze-drying Ti₃C₂T_x and in situ formation of Ti₃C₂T_x-Au nanocomposite. The fabricated aptasensor exhibited a very low detection limit (S/N ≥ 3) of 13.18 fg mL^-1 with a linear range of 1 ~ 700 pg mL^-1 and correlation coefficient of 0.9992. The fabricated aptasensor demonstrated an excellent reproducibility, repeatability, long-term stability, and high selectivity toward chloramphenicol. Further, the aptasensor was applied to real milk samples, and the recoveries were ranged from 98.93 to 101.93%.

Three-Dimensional Electrochemical Sensors for Food Safety Applications

Considering the increasing concern for food safety, electrochemical methods for detecting specific ingredients in the food are currently the most efficient method due to their low cost, fast response signal, high sensitivity, and ease of use. The detection efficiency of electrochemical sensors is determined by the electrode materials' electrochemical characteristics. Among them, three-dimensional (3D) electrodes have unique advantages in electronic transfer, adsorption capacity and exposure of active sites for energy storage, novel materials, and electrochemical sensing. Therefore, this review begins by outlining the benefits and drawbacks of 3D electrodes compared to other materials before going into more detail about how 3D materials are synthesized. Next, different types of 3D electrodes are outlined together with common modification techniques for enhancing electrochemical performance. After this, a demonstration of 3D electrochemical sensors for food safety applications, such as detecting components, additives, emerging pollutants, and bacteria in food, was given. Finally, improvement measures and development directions of electrodes with 3D electrochemical sensors are discussed. We think that this review will help with the creation of new 3D electrodes and offer fresh perspectives on how to achieve extremely sensitive electrochemical detection in the area of food safety.

Two colors, one-step, self-drive fluorescent strategy for chloramphenicol detection base on DNAzyme cleavage triggered hybridization chain reaction

A two colors, one-step, self-drive fluorescent strategy was developed for chloramphenicol (CAP) detection based on cyclic cleavage of molecular beacon (MB) by pincer DNA sequences. CAP can bind with its aptamer and active the enzyme-strand (E-DNA). Then the E-DNA can circularly cleave the MB on the both side of pincer DNA sequences. The cleaved fragments can self-assembly to form a long duplex and cause the great recovery of the two colors fluorescent signal. The limit of detection was as low as 0.7 pM. Importantly, the whole detection process is very simple with only one-step operation. Moreover, the two colors fluorescent signals can greatly enhance the accuracy of the result. It was also successfully used to detect CAP in actual samples.

Synthesis and application of quantum dots in detection of environmental contaminants in food: A comprehensive review

Environmental pollutants can accumulate in the human body through the food chain, which may seriously impact human health. Therefore, it is of vital importance to develop quick, simple, accurate and sensitive (respond quickly) technologies to evaluate the concentration of environmental pollutants in food. Quantum dots (QDs)-based fluorescence detection methods have great potential to overcome the shortcomings of traditional detection methods, such as long detection time, cumbersome detection procedures, and low sensitivity. This paper reviews the types and synthesis methods of QDs with a focus on green synthesis and the research progress on rapid detection of environmental pollutants (e.g., heavy metals, pesticides, and antibiotics) in food. Metal-based QDs, carbon-based QDs, and "top-down" and "bottom-up" synthesis methods are discussed in detail. In addition, research progress of QDs in detecting different environmental pollutants in food is discussed, especially, the practical application of these methods is analyzed. Finally, current challenges and future research directions of QDs-based detection technologies are critically discussed. Hydrothermal synthesis of carbon-based QDs with low toxicity from natural materials has a promising future. Research is needed on green synthesis of QDs, direct detection without pre-processing, and simultaneous detection of multiple contaminants. Finally, how to keep the mobile sensor stable, sensitive and easy to store is a hot topic in the future.

Development of europium(III) complex functionalized silica nanoprobe for luminescence detection of tetracycline

Increasing awareness of the health and environment impacts of the antibiotics misuse or overuse, such as tetracycline (TC) in treatment or prevention of infections and diseases, has driven the development of robust methods for their detection in biological, environmental and food systems. In this work, we report the development of a new europium(III) complex functionalized silica nanoprobe (SiNPs-Eu³⁺) for highly sensitive and selective detection of TC residue in aqueous solution and food samples (milk and meat). The nanoprobe is developed by immobilization of Eu³⁺ ion onto the surface of silica nanoparticles (SiNPs) as the emitter and TC recognition unit. The β-diketone configuration of TC can further coordinate with Eu³⁺ steadily on the surface of nanoprobe, facilitating the absorption of light excitation for Eu³⁺ emitter activation and luminescence "off-on" response. The dose-dependent luminescence enhancement of SiNPs-Eu³⁺ nanoprobe exhibits good linearities, allowing the quantitative detection of TC. The SiNPs-Eu³⁺ nanoprobe shows high sensitivity and selectivity for TC detection in buffer solution. Time resolved luminescence analysis enables the elimination of autofluorescence and light scattering for highly sensitive detection of TC in milk and pork mince with high accuracy and precision. The successful development of SiNPs-Eu³⁺ nanoprobe is anticipated to provide a rapid, economic, and robust approach for TC detection in real world samples.

Detection Enhancement of One Multifunctional Cd-Metal-Organic Framework toward Tetracycline Antibiotics by Simply Mixing Eu3+ in Suspension

It is necessary to find more simple methods to improve the detection selectivity and sensitivity of antibiotics. Herein, we constructed a novel three-dimensional (3D) Cd-MOF LCU-117 assembled from p-terphenyl-4,2″,5″,4'-tetracarboxylic acid, which showed a special 3D helical structure with carboxylic acid ligands and nitrogen-containing ligands crossing each other vertically. Luminescence measurements indicated that LCU-117 has high selectivity and sensitivity toward Eu³⁺ through the ratiometric effect. Meanwhile, this complex itself could detect antibiotics oxytetracycline (OTC) through the turn-off mechanism. When Eu³⁺ was added in suspensions of LCU-117 (noted as Eu³⁺@LCU-117), the detection toward OTC was enhanced significantly and visually. The sensing mechanism was investigated in detail by various measurements and theoretical calculations. LCU-117 has a good effect on the logic gate, potential fingerprint detection, and mixed-matrix membranes (MMMs). The practical application for monitoring OTC in water samples also provided a satisfactory result.

Group-targeting sulfonamides via an evanescent-wave biosensor based on rational designed coating antigen

In order to effectively monitor a wide variety of sulfonamides residues in the environment, group-targeting immunoassay based on the group-specific antibodies has attracted great attentions, which can realize the detection of a group of contaminants in environment as many as possible even the unrecognized ones. Indirect competitive immunoassay is generally adopted for small molecule detection however the rational design of immobilized coating antigen for improved recognition capability on the solid surface is far from enough. To cover the research gap, we proposed the design criteria of coating antigen for surface-based indirect competitive immunoassay based on the molecular docking. Taking the group-specific antibodies against sulfonamides (SA) as a proof-of-concept, a hapten with a linking arm with 3 methyl groups was selected to synthesize the coating antigen. Through surface immobilization of coating antigen, a portable biosensor for group-targeting immunoassay of sulfonamides was developed and demonstrated excellent performance with detection limits lower than 0.6 μg/L for four SA variants, and the cross-reactivities of 148-215 % relative to sulfadiazine. The recovery rates of SAs in liquid milk ranges from 87 to 97 %, which confirmed the application potential of this method in the determination of SAs. Its capability to measure total SAs in a simple and low-cost way would pave the way for a variety of application fields.

Facile room temperature synthesis of a NiFe2O4-based magnetic covalent organic framework for the extraction of tetracycline residues in environmental water samples prior to HPLC

In this study, a functionalized magnetic covalent organic framework (NiFe₂O₄@TAPB-TPA) was fabricated with NiFe₂O₄ nanoparticles as the magnetic core, and 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehyde (TPA) as building blocks by a facile room temperature strategy. Benefitting from the π-π stacking and hydrogen bond interaction, NiFe₂O₄@TAPB-TPA showed great potential as a magnetic adsorbent for the extraction of tetracyclines (TCs). Under optimal conditions, good linearities (R² > 0.9990) were obtained between the peak area and TC concentration in the range of 1-500 μg L^-1 with limits of detection ranging from 0.09 to 0.26 μg L^-1. The intra-day and inter-day relative standard deviations were less than 2.2% and 4.7%, respectively. The established method was successfully applied for the determination of TCs in diverse environmental water samples with satisfactory recoveries in the range of 91.6-102.7%. In addition, NiFe₂O₄@TAPB-TPA showed good reusability with the recoveries for TCs higher than 73.1% after nine recycles, indicating potential application of NiFe₂O₄@TAPB-TPA as an ideal adsorbent for the enrichment of TCs.

Recent advances in electrochemical-based sensors amplified with carbon-based nanomaterials (CNMs) for sensing pharmaceutical and food pollutants

Foodborne-related infections due to additives and pollutants pose a considerable task for food processing enterprises. Therefore, the competent, cost-effective, and quick investigation of nutrition additives and contaminants is essential to reduce the threat of public fitness problems. The electrochemical sensor (ECS) shows facile and potent analytical approaches desirable for food protection and quality inspection over traditional methods. The consequence of a broad display of nanomaterials has paved the path for their relevance in designing high-performance ECSs appliances for medical diagnostics and conditions and food protection. This review article has discussed the importance of electrochemical-based sensors amplified with carbon-based nanomaterials (CNMs). Initially, we have demonstrated the types of pharmaceutical and food/agriculture pollutants (such as pesticides, heavy metals, antibiotics and other medical drugs) present in water. Subsequently, we have compiled the information on electrochemical techniques (such as voltammetric and electrochemical impedance spectroscopy) and their crucial parameters for detecting pollutants. Further, the applications of CNMs for sensing pharmaceutical and food pollutants have been demonstrated in detail. Finally, the topic has been concluded with existing challenges and future prospects.

Seasonal Pollution Characteristics of Antibiotics on Pig Farms of Different Scales

Scientific interest in pollution from veterinary antibiotics (VAs) on intensive animal farms has been increasing in recent years. However, limited information is available on the seasonal pollution characteristics and the associated ecological risks of VAs, especially about the different scale farms. Therefore, this study investigated the seasonal pollution status and ecological risks of 42 typical VAs (5 classes) on three different scale pig farms (breeding scales of about 30,000, 1200, and 300 heads, respectively) in Tianjin, China. The results showed that large-scale pig farms usually had the highest antibiotic pollution levels, followed by small-scale pig farms and medium-scale pig farms. Among different seasons, antibiotic contamination was more severe in winter and spring than that in the other seasons. Tetracyclines (TCs) usually had higher proportions (over 51.46%) and the residual concentration detected in manure, and wastewater samples ranged from not detected (ND)-1132.64 mg/kg and ND-1692.50 μg/L, respectively, which all occurred for oxytetracycline (OTC) during winter. For the antibiotic ecological risks in the effluent, we found high-risk level of 12 selected VAs accounted for 58% in spring, and 7 kinds of VAs were selected in the amended soil, but nearly all the antibiotics had no obvious ecological risks except OTC (spring and summer). All these data provided an insight into the seasonal variability and the associated ecological risks of antibiotics on intensive pig farms, which can provide scientific guidance on decreasing antibiotic contamination to enhance environmental security in similar areas.

Occurrence of quinolones in cultured fish from Shandong Province, China and their health risk assessment

The residue levels of 6 quinolones in 160 cultured fish samples from Shandong Province, China were investigated using UPLC-MS/MS. The detection rate was 43.1% and enrofloxacin had the highest detection rate as well as the highest residue concentration. The violation rates were 2.50% for the sum of enrofloxacin and ciprofloxacin and 1.25% for ofloxacin. Among the 9 fish species, quinolone contamination problems should receive more attention in Carp, Grass carp, Crucian and Catfish. The health risk assessment showed that when calculated by the maximum concentration, the estimated daily intakes (EDIs) of Carp, Grass carp and Crucian for the high consumption group accounted for more than 10% of the acceptable daily intakes (ADIs), indicating that a large intake of these fish species might pose a potential health risk and health risk monitoring of quinolones in cultured fish should be continually performed.

Portable and on-site electrochemical sensor based on surface molecularly imprinted magnetic covalent organic framework for the rapid detection of tetracycline in food

In this study, for the first time, surface molecularly imprinted magnetic covalent organic frameworks (Fe₃O₄@COFs@MIPs) were combined with disposable screen-printed electrode (SPE) to construct a portable and on-site electrochemical sensor for the rapid detection of tetracycline (TC). The Fe₃O₄@COFs@MIPs, which was prepared by layer-by-layer modification method, had good magnetism and excellent adsorption ability. With the help of disposable SPE, equipped with a magnet, the electrode modification process was simplified and the detection efficiency was improved. Under optimal conditions, the fabricated electrochemical sensor exhibited linearity ranging from 1 × 10^-10 to 1 × 10^-4 g mL^-1. It had good selectivity, excellent reproducibility, desirable stability and remarkable applicability. The fabricated sensor was successfully applied to detect TC in real samples with satisfactory recoveries (96.15-106.20%). The detection strategy separated the recognition and adsorption process from the electrochemical detection process, providing a design idea for the application of COFs in the construction of high-efficiency molecularly imprinted electrochemical sensors.

Colorimetric assay for tetracyclines based on europium ion-induced aggregation of gold nanoparticles

Oxytetracycline-capped gold nanoparticles (OTC-Au NPs) were prepared using sodium borohydride as the reductant and OTC as the capping agent, respectively. The prepared OTC-Au NPs with a size of 6 nm have a maximum surface plasma resonance (SPR) absorption located at 514 nm. The OTC on the surface of Au NPs still can coordinate with Eu³⁺ ions. Due to the property that OTC has multivalent binding sites with Eu³⁺ ions, Eu³⁺ ions can induce the aggregation of OTC-Au NPs. Based on the Eu³⁺ ions-aggregated OTC-Au NPs, a simple aptamer-free colorimetric sensing method for TCs was developed. Briefly, free TCs compete with OTC on the surface of Au NPs resulting in the change of OTC-Au NPs from an aggregation state to a dispersed state. The whole process takes only 5 min, and as low as 20 nM OTC, 14 nM tetracycline (TC), and 20 nM doxycycline (DC) could be sensitively detected, respectively. The proposed method was also featured as good repeatability and specificity, and was applied to the detection of OTC in lake water with satisfactory recovery.

Stable Metal-Organic Frameworks for Fluorescent Detection of Tetracycline Antibiotics

The rapid detection of antibiotics in agricultural products is of great significance. In this work, two stable fluorescent metal-organic frameworks (MOFs), BUT-178 and BUT-179, are synthesized and used to detect tetracycline antibiotics. Among them, BUT-179 exhibits better performance in the detection of different tetracycline antibiotics in water and eggs. The limits of detection of BUT-179 toward tetracycline, aureomycin, oxytetracycline, and doxycycline all reach the nanomolar level. Furthermore, the cycling tests confirm that BUT-179 can be easily recovered and repeatedly used without an obvious performance loss. This work demonstrates the excellent application potential of MOFs for food safety, especially the fluorescence detection of antibiotics in foods.

Microbial Acoustical Analyzer for Antibiotic Indication

In this study, a compact acoustic analyzer for express analysis of antibiotics based on a piezoelectric resonator with a lateral electric field and combined with a computer was developed. The possibility of determining chloramphenicol in aqueous solutions in the concentration range of 0.5-15 μg/mL was shown. Bacterial cells that are sensitive to this antibiotic were used as a sensory element. The change in the electrical impedance modulus of the resonator upon addition of the antibiotic to the cell suspension served as an analytical signal. The analysis time did not exceed 4 min. The correlation of the experimental results of an acoustic sensor with the results obtained using the light phase-contrast microscopy and standard microbiological analysis was established. The compact biological analyzer demonstrated stability, reproducibility, and repeatability of results.

Simultaneous determination of the four key fluoroquinolones and two antipsychotics in fish and shrimp by LC-MS/MS

In this study, we developed and validated a liquid chromatography triple quadrupole tandem mass spectrometry (LC-MS/MS) method used to simultaneously determine levels of four fluoroquinolones (ofloxacin, norfloxacin, lomefloxacin, and pefloxacin) and two antipsychotics (diazepam and methaqualone) in fish and shrimp. The samples were extracted with a mixture of anhydrous sodium sulfate and acetonitrile, and purified by C₁₈ cartridge solid-phase extraction with an optimized eluent. The MS² method was applied to recognize the molecular structure of these compounds according to a main fragmentation scheme. The key ions of identification and quantification were deduced from chemical structures. Multiple reaction monitoring was used to quantitatively analyse the compounds of interest. Satisfactory linearities were obtained (R² ≥0.99) with the limits of quantitation (LOQs) ranging between 0.03 and 1.96 μg kg^-1. The recoveries were 74-122%, with a relative standard deviation (RSD) below 4.9% for these compounds at the spiking level of three, five, and ten times the LODs, respectively. The LC-MS/MS method allows precise and sensitive determination of residues of six important banned veterinary drugs in fish and shrimp tissue. This methodological approach solved the problem imposed by the need for two or more analysis methods to analyse the compounds of interest described in this study.

An upconversion nanosensor for rapid and sensitive detection of tetracycline in food based on magnetic-field-assisted separation

Tetracycline, a broad-spectrum antibiotic, has been widely used in disease treatment and other fields. However, due to the unreasonable use, its residue remains in food which eventually harms human health. Here described an upconversion nanosensor for tetracycline detection based on magnetic separation and electrostatic adsorption. To identify tetracycline, tetracycline aptamer, and europium ions (Eu³⁺) were introduced in the system. According to the electrostatic adsorption principle, Eu³⁺ exposed core-shell UCNPs were bound to negative complex of magnetic nanoparticles (MNPs) and aptamer. In the presence of tetracycline, UCNPs separated with MNPs-aptamer and remained in the supernatant by an external magnetic field. Under optimal conditions, the linear detection range of tetracycline was 0.5-1000 ng·mL^-1, and the detection limit was 0.17 ng·mL^-1. It has been successfully applied to detect tetracycline in food samples. The constructed method provided broad prospects for tetracycline detection with the merits of simple operation, high sensitivity, excellent repeatability, and selectivity.

MXene-AuNP-Based Electrochemical Aptasensor for Ultra-Sensitive Detection of Chloramphenicol in Honey

A simple and label-free electrochemical aptasensor was developed for ultra-sensitive determination of chloramphenicol (CAP) based on a 2D transition of metal carbides (MXene) loaded with gold nanoparticles (AuNPs). The embedded AuNPs not only inhibit the aggregation of MXene sheets, but also improve the quantity of active sites and electronic conductivity. The aptamers (Apts) were able to immobilize on the MXene–AuNP modified electrode surface through Au–S interaction. Upon specifically binding with CAP with high affinity, the CAP–Apt complexes produced low conductivity on the aptasensor surface, leading to a decreased electrochemical signal. The resulting current change was quantitatively correlated with CAP concentration. Under optimized experimental conditions, the constructed aptasensor exhibited a good linear relationship within a wide range of 0.0001–10 nM and with a low detection limit of 0.03 pM for CAP. Moreover, the developed aptasensor has been applied to the determination of CAP concentration in honey samples with satisfactory results.

Antibiotic residues in poultry tissues in Iran: A systematic review and meta-analysis

To control the drug residues in foods, the national Maximum Residue Limits (MRLs) have been determined by the international organizations; however, no regulation has been complied for MRL in food animals in Iran. This study was a systematic review and meta-analysis about studies of antibiotic residues in slaughtered poultry carcasses, in Iran. The information was first collected and analyzed throughout six international databases, and four Iranian national databases. According to the data, the total prevalence of antibiotic residues was obtained as 39.41%, 5.40%, and 0.30% using four-plate test (FPT), High-Performance Liquid Chromatography (HPLC), and Enzyme-linked immuno_sorbent assay (ELISA) methods, respectively. The highest prevalence of the residues was shown in the liver by both methods of HPLC (47.75%) and ELISA (14.35%). Moreover, the total mean of antibiotics was recorded as 71.03 ppb and 65.86 ppb in different tissues using the HPLC and ELISA method, respectively. Based on this study, we can conclude that the prevalence of antibiotic residue in poultry meat in Iran is high and that this level does not cause health problems for consumers. It is highly recommended to execute tight surveillance strategies from the government in antibiotic monitoring.

Validation method for determining enrofloxacin and tylosin levels in broiler liver, kidney, and muscle using high-performance liquid chromatography

Background and Aim: Enrofloxacin and tylosin can be combined into an antibiotic formulation which is expected to have a broader range of antibacterial activity against various infections in broilers. Validation method analysis of the levels of these two active compounds needs to be done for future use in pharmacokinetic or residual studies. The present study aims to determine a suitable validation method of isocratic high-performance liquid chromatography (HPLC) to measure the concentration of antibiotic combinations in the broiler liver, kidney, and muscles. Materials and Methods: The combination of enrofloxacin and tylosin in the liver, kidney, and muscle was validated by HPLC method to find the procedures, processes, equipment, and systems used, consistently provides the appropriate results. The chromatography system consisted of an Octadecyl-silica column of 5 μm in diameter and 150 mm in length with a mobile phase of a mixture of 0.05 M monobasic sodium phosphate (pH 2.5) and acetonitrile (65:35 v/v). The solution was detected at a wavelength of 280 nm, 30°C, a flow rate of 1 mL/min, and an injection volume of 20 μL. The combination antibiotics powder was produced from PT Tekad Mandiri Citra, Bandung, Indonesia, and broiler tissues obtained from day-old chick broilers maintained for 30 days with free antibiotic feed. Results: Validation of a combination solution of enrofloxacin and tylosin shows the linearity values of enrofloxacin and tylosin in the liver, kidney, and muscles as r2=0.9988, r2=0.9999, r2=0.9997, r2=0.9989, r2=0.9978, and r2=0.9962. The accuracy and precision values of enrofloxacin in the liver, kidney, and muscles were 5.53, 6.23, and 6.93, respectively. The values of accuracy and precision of tylosin in the liver, kidney, and muscles were 10.43, 4.63, and 7.16%, respectively. The retention times for enrofloxacin and tylosin were 1.945-2.000 min and 4.175-4.342 min. The limit of detection (LOD) and limit of quantity (LOQ) values for enrofloxacin were 3.03 and 10.1 μg/g, respectively. In contrast, the LOD and LOQ values for tylosin were 9.05 and 30.17 μg/g, respectively. Conclusion: The value of linearity, accuracy, precision, specificity, and sensitivity of the combined solution of enrofloxacin and tylosin showed promising results.