An overview of the main foodstuff sample preparation technologies for tetracycline residue determination

Earthworms and lactic acid bacteria (LAB) cooperate to promote the biodegradation of tetracycline residues in livestock manure

Tetracycline is an antibiotic with extensive veterinary use in the livestock industry. However, their widespread application poses risks to soil health as residue in livestock feces, and their removal is crucial for sustainable soil-ecosystem development. Physical and chemical approaches to extract tetracycline may have adverse effects on soil ecosystems, but no studies have thus far examined the potential for biological methods, such as collective degradation action of soil fauna. Thus, this study aimed to investigate the synergistic effects of lactic acid bacteria (LAB) and earthworms (Eisenia fetida) on biodegradation of tetracycline residues in sheep manure. We assessed earthworm biomass, tetracycline residue, and bacterial communities in both earthworm intestines and vermicompost. Earthworm biomass and tetracycline degradation efficiency increased significantly with LAB addition, with a degradation rate of up to 80.16%. This increase may be attributable to LAB acting as electron donors to spur tetracycline degradation. Additionally, we noted that tetracycline presence significantly influenced bacterial communities in earthworm intestines and vermicompost, elevating the abundance of potential pathogenic bacteria (e.g., Flavobacterium, Gammaproteobacteria, and Enterobacteriaceae). This finding suggests that heightened environmental stress from antibiotics could actually facilitate the growth of less prevalent bacteria, including potential pathogens. In conclusion, our study provides evidence supporting the effectiveness of LAB and earthworms in degrading tetracycline residues. In particular, LAB appears to mitigate stress from tetracycline exposure in earthworms, thus increasing their vermicomposting efficacy. Our work has important implications for soil management, with the potential to enhance pollution clean-up rates while minimizing negative side-effects to soil microbial communities.

Synthesis of N-doped and P-doped silicon quantum dots and their applications for tetracycline detection in the honey samples and antibacterial properties

The abuse of tetracycline can lead to its residue in animal derived foods, posing many potential hazards to human health. Therefore, rapid and accurate detection of tetracycline is an important means to ensure food safety. Nitrogen doped and phosphorus doped silicon quantum dots (N-SiQDs, P-SiQDs) with remarkable optical stability were fabricated via a one-pot hydrothermal procedure in this study. Upon the excitation at 346 nm, N-SiQDs and P-SiQDs emitted fluorescence at 431 nm and 505 nm, respectively. Two SiQDs had the potential to serve as a probe for detecting low concentrations of tetracycline (TC), employing a mechanism of the static quenching effect. The calibration curves of N-SiQDs and P-SiQDs were linear within the range of 0-0.8 μM and 0-0.4 μM, the limits of detection were low as 5.35 × 10-4 μmol/L and 6.90 × 10-3 μmol/L, respectively. This method could be used successfully to detect TC in honey samples. Moreover, the remarkable antibacterial efficacy of two SiQDs could be attributed to the generation of a large number of intracellular reactive oxygen species. The SEM images showed that the structure of bacterial cell was disrupted and the surface became irregular when treated with both SiQDs. These properties enabled potential usage of SiQDs as excellent antibacterial material for different biomedical applications.

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.

Molecular spectra and docking simulations investigated the binding mechanisms of tetracycline onto E. coli extracellular polymeric substances

Extracellular polymeric substances (EPS), which were an important fraction of natural organic matter (NOM), played an important role in various environmental processes. However, the heterogeneity, complexity, and dynamics of EPS make their interactions with antibiotics elusive. Using advanced multispectral technology, this study examined how EPS interacts with different concentrations of tetracycline (TC) in the soil system. Our results demonstrated that protein-like (C1), fulvic-like (C2), and humic-like (C3) fractions were identified from EPS. Two-dimensional synchronous correlation spectroscopy (2D-SF-COS) indicated that the protein-like fraction gave faster responses than the fulvic-like fraction during the TC binding process. The sequence of structural changes in EPS due to TC binding was revealed by two-dimensional Fourier Transformation Infrared correlation spectroscopy (2D-FTIR-COS) as follows: 1550 > 1660 > 1395 > 1240 > 1087 cm-1. It is noteworthy that the sensitivity of the amide group to TC has been preserved, with its intensity gradually increasing to become the primary binding site for TC. The integration of hetero-2DCOS maps with moving window 2D correlation spectroscopy (MW2DCOS) provided a unique insight into understanding the correlation between EPS fractions and functional groups during the TC binding process. Moreover, molecular docking (MD) discovered that the extracellular proteins would provide plenty of binding sites with TC through salt bridges, hydrogen bonds, and π-π base-stacking forces. With these results, systematic investigations of the dynamic changes in EPS components under different concentrations of antibiotic exposure demonstrated the advanced capabilities of multispectral technology in examining intricate interactions with EPS in the soil environment.

Visible light photocatalytic degradation of oxytetracycline hydrochloride using chitosan-loaded Z-scheme heterostructured material BiOCOOH/O-gC3N4

In this work, a Z-scheme heterostructured BiOCOOH/O-gC3N4 material was synthesized and immobilized on chitosan (CTS) to obtain the BiOCOOH/O-gC3N4/CTS photocatalytic material for photocatalytic degradation of oxytetracycline hydrochloride (CTC).Our findings indicate that the composite material BiOCOOH/O-gC3N4, as well as the BiOCOOH/O-gC3N4/CTS composite membrane, displayed a significantly higher efficiency in photocatalytic degradation of CTC compared to BiOCOOH alone, owing to the synergistic effect of adsorption and photocatalysis. Following four cycles of use, the composite material retained around 96 % of its initial photocatalytic degradation activity. The addition of CTS in the photocatalytic material resolved issues such as aggregation and difficult recovery commonly encountered with powder materials, thereby facilitating effective collision between the photocatalytic active sites and CTC. Experimental and theoretical calculations provided confirmation that the combination of BiOCOOH and O-gC3N4 effectively enhanced the light absorption capacity and photocatalytic performance. Furthermore, we investigated the influence of environmental factors such as pH value and anions on the photocatalytic degradation experiment, which offers valuable insights for the application of composite catalysts in wastewater treatment.

Quantitative determination of tetracyclines in medicated feed for food-producing animals by HPLC-DAD

Tetracyclines are a group of antibiotic substances largely administered through medicated feed to control diseases in food-producing animals. Fine dosing of antibiotics contained in medicated feed is crucial for the success of the treatment as well as minimising potential threats such as the spread of antimicrobial resistance and the transfer of antibiotic residues in food. A rapid analytical method based on HPLC with diode array detection (HPLC-DAD) was developed to quantify oxytetracycline, chlortetracycline and doxycycline in medicated feed. The reported method underwent in-house validation and was found to be suitable for the quantification of three target tetracyclines within the concentration range of 40-1000 mg kg-1 in official routine analysis. The method was applied to 103 official samples in the framework of the Italian National Plan on animal feed during the years 2021-2023 and nine non-compliant concentrations were identified in swine and fish feed samples.

An antifouling electrochemical aptasensor based on a polydopamine-polyzwitterion copolymer for tetracycline analysis

Matrix interference resulting from the nonspecific adsorption of non-target components, particularly proteins (fouling), onto sensor surfaces poses a persistent challenge in electrochemical detection of food hazards. The development of antifouling sensor surfaces presents a viable approach to mitigate nonspecific adsorption. In this study, a novel antifouling electrochemical aptasensor, utilizing a zwitterionic polymer, was developed for the sensitive, accurate, and selective detection of tetracycline (TC) in milk. This sensor employs a poly (dopamine)-poly (sulfobetaine methacrylate) (PDA-PSBMA) antifouling copolymer, which is synthesized through an in-situ initiated copolymerization of dopamine on the sensor's surface. Subsequently, the thiol-containing aptamers were immobilized onto the PDA-PSBMA coating through a Michael addition reaction with the poly(dopamine). The resulting antifouling electrochemical aptasensor exhibited robust antifouling performance in various single protein solutions and diluted milk samples, coupled with sensitive and selective recognition of TC. The sensor demonstrated a broad linear response range of 0.1-1000.0 ng mL-1 and a low limit of detection (LOD) of 68.0 pg mL-1. The antifouling electrochemical aptasensor proved effective in assaying TC in diluted milk, with recoveries ranging from 100.0 % to 104.4 %, eliminating the need for additional pretreatments due to its exceptional resistance to nonspecific adhesion.

Green hairy basil seed mucilage biosorbent for dispersive solid phase extraction enrichment of tetracyclines in bovine milk samples followed by HPLC analysis

Unmodified hairy basil seed mucilage (Ocimum basilicum L.), with attractive features as structural functionality and adsorption capacity, was employed as a green biosorbent for dispersive solid phase extraction and enrichment of oxytetracycline, tetracycline, and doxycycline before quantitation by HPLC-UV for the first time. Hairy basil crushed seed increased the contacting surface area and was completely dispersed in the sample solution to extract tetracyclines under acidic condition with the assistance of ultrasonic waves. The analytes in the extraction phase were separated on a C18 column under isocratic condition with a mobile phase consisted of acetonitrile and trifluoroacetic acid. Influence of chemical and physical variables on the extraction efficiency of the developed method was investigated and optimized systematically. Under the optimal condition of all experimental parameters, good linear ranges were obtained at 15.0-500 μg L-1 for tetracyclines with determination coefficients more than 0.9994. Limits of detection (LODs) and limits of quantitation (LOQs) ranged 5.0-7.0 and 15.0 μg L-1, respectively. Relative standard deviations (RSDs) of the proposed method at 100 and 300 μg L-1 for TCs were less than 13 % and 10 %, respectively with percentage TC recoveries from spiked standard ranging 83.1-109.9 %. This simple, reliable, cost-effective, and environmentally friendly method was successfully applied for the analysis of tetracycline residues in milk. The greenness of the proposed method was assessed using the Analytical Eco-Scale and AGREE protocol.

Construction of a stable fluorescent sensor based on CsPbBr3/CdS core/shell quantum dots for selective and sensitive detection of tetracycline in ethanol

The weakly bound organic ligand shells around perovskite quantum dots (QDs) are easily decomposed and cannot provide sufficient stability in polar solvents, which greatly obstructs their applications in sensing. Herein, a fluorescent sensor based on CsPbBr3/CdS core/shell QDs was developed for the detection of tetracycline (TC) in the polar solvent-ethanol. Pristine CsPbBr3 QDs were treated with cadmium diethyldithiocarbamate (Cd(DDTC)2) to form a shell on the surface at 110 °C, while extra oleylammonium bromide (OAmBr) was added to inhibit the phase transformation of CsPbBr3 into a Cs4PbBr6 impurity phase during high-temperature processing. And finally CsPbBr3/CdS core/shell QDs were successfully synthesized. The capping with the CdS inorganic shell remediated surface defects and improved the stability in ethanol without affecting the emission properties of the parent CsPbBr3 QDs. The results showed that the fluorescent sensor detected TC in the range of 0.05-25 μM with a low detection limit of 22.6 nM, whereas it had high selectivity and anti-interference ability for TC. And the fluorescence quenching mechanism of the sensor was mainly photoinduced electron transfer between TC and CsPbBr3/CdS QDs. Our research provides a unique way to improve the stability of perovskite QDs in polar solvents and applications in fluorescence detection.

Automated method for the solid phase extraction of tetracyclines in wastewater followed by fluorimetric determination

This work presents a multisyringe flow injection analysis (MSFIA) system for the automatic extraction and determination of tetracyclines in wastewater samples. The sample was adjusted with Na2EDTA buffer before solid-phase extraction with an Oasis HLB column used for the analyte preconcentration. The europium (Eu3+)-based and citrate-mediated method (using Tris-HCl buffer) was selected for the fluorimetric analysis (λexc/em = 400/612 nm). For fluorescence detection, a low-cost system consisting of an USB 2000 CCD detector and a 3D-printed support that holds a LED light source was used. Under optimized conditions, the proposed method provided low limits of detection (9.4 μg L-1) and quantification (31 μg L-1), and good values for intra-day (<4 %) and inter-day precisions (<6 %). Recoveries of spiked TCs in wastewater samples ranged from 87 to 106 %. The results of this work were in good agreement with the measurements obtained by liquid chromatography coupled to a fluorescence detector.

Development of a Cation Exchange SPE-HILIC-MS/MS Method for the Determination of Ningnanmycin Residues in Tea and Chrysanthemum

Ningnanmycin is a widely used antibiotic in agricultural production that effectively controls fungal and viral diseases in tea trees and chrysanthemums. The polarity characteristic of ningnanmycin has posed limitations on the development of robust detection methods, thereby hindering effective monitoring and control measures. By combining cation exchange solid phase extraction (SPE) with hydrophilic interaction chromatography tandem mass spectrometry (HILIC-MS/MS), we have effectively tackled the issue pertaining to the separation and retention of ningnanmycin. The average recoveries of ningnanmycin in green tea, black tea, and chrysanthemum were 77.3-82.0%, 80.1-81.5%, and 74.0-80.0%, respectively. The intraday and interday relative standard deviations (RSDs) were below and equal to 7.7%. Good linearity was observed in the concentration range of 1-1000 μg/L (R2 > 0.998). The limits of detection (LODs) ranged from 1.1 μg/kg to 7.1 μg/kg, and the limits of quantification (LOQs) ranged from 3.6 μg/kg to 23.7 μg/kg for ningnanmycin. These results indicate the good accuracy, repeatability, reproducibility, and sensitivity of the method. It is suitable for detecting ningnanmycin in tea and chrysanthemum.

Significant Differences in the Effects of Nitrogen Doping on Pristine Biochar and Graphene-like Biochar for the Adsorption of Tetracycline

To improve the adsorption efficiency of pollutants by biochar, preparing graphene-like biochar (GBC) or nitrogen-doped biochar are two commonly used methods. However, the difference in the nitrogen doping (N-doping) effects upon the adsorption of pollutants by pristine biochar (PBC) and GBC, as well as the underlying mechanisms, are still unclear. Take the tetracycline (TC) as an example, the present study analyzed the characteristics of the adsorption of TCs on biochars (PBC, GBC, N-PBC, N-GBC), and significant differences in the effects of N-doping on the adsorption of TCs by PBC and GBC were consistently observed at different solution properties. Specifically, N-doping had varied effects on the adsorption performance of PBC, whereas it uniformly improved the adsorption performance of GBC. To interpret the phenomenon, the N-doping upon the adsorption was revealed by the QSAR model, which indicated that the pore filling (VM) and the interactions between TCs with biochars (Ead-v) were found to be the most important two factors. Furthermore, the density functional theory (DFT) results demonstrated that N-doping slightly affects biochar's chemical reactivity. The van der Waals (vdWs) and electrostatic interactions are the main forces for TCs-biochars interactions. Moreover, N-doping mostly strengthened the electrostatic interactions of TCs-biochars, but the vdWs interactions of most samples remained largely unaffected. Overall, the revealed mechanism of N-doping on TCs adsorption by biochars will enhance our knowledge of antibiotic pollution remediation.

A smartphone-assisted paper-based ratio fluorescent probe for the rapid and on-site detection of tetracycline in food samples

Rapid, sensitive and portable analytical methods for on-site detection of tetracycline (TC) in food samples is of critical importance for food safety and public health. In this study, a dual-emission ratio fluorescent probe (Gd0.9@Eu0.1) was prepared and utilized for the detection of tetracycline (TC) by observing the fluorescence color change from blue to red. The detection process exhibits a wide linear range (0-52.0 μM), good selectivity and low detection limit (14 nM). A paper-based probe and a colorimetric card was constructed for the visual detection of TC. Furthermore, a novel and portable detection platform combining smartphone and test strip was exploited for the quantitative and on-site detection of TC in real pork sample. The developed method was validated through intra- (n = 5) and inter-day (n = 2) measurements, as well as comparison with a traditional HPLC method. These statistical result validate the reliability and accuracy of the developed method. This intelligent detection platform represents a promising approach for the rapid, sensitive and visual detection of TC in food samples.

Directed evolution of TetR for constructing sensitive and broad-spectrum tetracycline antibiotics whole-cell biosensor

Antibiotic abuse is the main reason for the drug resistance of pathogenic bacteria, posing a potential health risk. Antibiotic surveillance is critical for preventing antibiotic contamination. This study aimed to develop a sensitive and broad-spectrum whole-cell biosensor for tetracycline antibiotics (TCs) detection. Wild-type TCs-responsive biosensor was constructed by introducing a tetracycline operon into a sfGFP reporter plasmid. Using error-prone PCR, mutation libraries containing approximately 107 variants of the tetracycline repressor (TetR) gene were generated. The tigecycline-senstive mutants were isolated using high-throughput flow cytometric sorting. After 2 rounds of directed evolution, a mutant epS2-22 of TerR was isolated and assembled as a TCs biosensor. The epS2-22 biosensor was more sensitive and broad-spectrum than the wild-type biosensors. The detection limits of the epS2-22 biosensor for seven TCs were 4- to 62-fold lower than the wild-type biosensor (no response to tigecycline). Meanwhile, the epS2-22 biosensor had a shorter detection time and a stronger signal output than the wild type. In addition, the evolved epS2-22 biosensor showed excellent performance in detecting low traces of TCs in environmental water. These results suggest that directed evolution is a powerful tool for developing high-performance whole-cell biosensors, and the evolved epS2-22 biosensors have the potential for wider applications in real-world TCs detection.

Simultaneous determination of six antibiotics belonging to four different classes in chicken meat BY HPLC/DAD and verification BY LC-MS/MS

The hypothesis of this study was to develop an extraction method allowing side-by-side extraction of six antibiotics belonging to four different classes and an HPLC/DAD method for the determination of their residues in chicken breast meat. The validation data showed that this hypothesis was achieved. The results were then confirmed by LC-MS/MS method. Sample preparation was based on the classical solid-liquid extraction with methanolic citric acid. The average recoveries were satisfactory and ranged from 75.68 to 101.3%. The linearity of the developed HPLC/DAD method was very high in the concentration range studied (R² > 0.9969). The accuracy and precision of the analytical method were between -10.8 and 12.0% relative error and 0.82 to 10.1% relative standard deviation, respectively. The LODs for five antibiotics ranged from 0.6 to 2.7 µg kg^-1 and LOQs ranged from 2.0 to 8.9 µg kg^-1. For penicillin G, the LOD was 0.16 and LOQ was 0.52 mg kg^-1.

Lab-made 3D-printed electrochemical sensors for tetracycline determination

Antibiotics such as tetracycline (TC) are widely prescribed to treat humans or dairy animals. Therefore, it is important to establish affordable devices in laboratories with minimal infrastructure. 3D printing has proven to be a powerful and cost-effective tool that revolutionizes many applications in electrochemical sensing. In this work, we employ a conductive filament based on graphite (Gr) and polylactic acid (PLA) (40:60; w/w; synthesized in our lab) to manufacture 3D-printed electrodes. This electrode was used "as printed" and coupled to batch injection analysis with amperometric detection (BIA-AD) for TC sensing. Preliminary studies by cyclic voltammetry and differential pulse voltammetry revealed a mass transport governed by adsorption of the species and consequent fouling of the redox products on the 3D printed surface. Thus, a simple strategy (solution stirring and application of successive potentials, +0.95 V followed by +1.2 V) was associated with the BIA-AD system to solve this effect. The proposed electrode showed analytical performance comparable to costly conventional electrodes with linear response ranging from 0.5 to 50 μmol L^-1 and a detection limit of 0.19 μmol L^-1. Additionally, the developed method was applied to pharmaceutical, tap water, and milk samples, which required minimal sample preparation (simple dilution). Recovery values of 92-117% were obtained for tap water and milk samples, while the content found of TC in the capsule was close to the value reported by the manufacturer. These results indicate the feasibility of the method for routine analysis involving environmental, pharmaceutical, and food samples.

Advances in solid-phase extraction techniques: Role of nanosorbents for the enrichment of antibiotics for analytical quantification

Antibiotics are life-saving medications for treating bacterial infections; however it has been discovered that resistance developed by bacteria against these incredible agents is the primary contributing factor to rising global mortality rates. The fundamental cause of the emergence of antibiotic resistance in bacteria is the presence of antibiotic residues in various environmental matrices. Although antibiotics are present in diluted form in environmental matrices like water, consistent exposure of bacteria to these minute levels is enough for the resistance to develop. So, identifying these tiny concentrations of numerous antibiotics in various and complicated matrices will be a crucial step in controlling their disposal in those matrices. Solid phase extraction, a popular and customizable extraction technology, was developed according to the aspirations of the researchers. It is a unique alternative technique that could be implemented either alone or in combination with other approaches at different stages because of the multitude of sorbent varieties and techniques. Initially, sorbents are utilized for extraction in their natural state. The basic sorbent has been modified over time with nanoparticles and multilayer sorbents, which have indeed helped to accomplish the desired extraction efficiencies. Among the current traditional extraction techniques such as liquid-liquid extraction, protein precipitation, and salting out techniques, solid-phase extractions (SPE) with nanosorbents are most productive because, they can be automated, selective, and can be integrated with other extraction techniques. This review aims to provide a broad overview of advancements and developments in sorbents with a specific emphasis on the applications of SPE techniques used for antibiotic detection and quantification in various matrices in the last two decades.

Synergistic Effects of Magnetic Z-Scheme g-C3N4/CoFe2O4 Nanofibres with Controllable Morphology on Photocatalytic Activity

The rational design of interfacial contacts plays a decisive role in improving interfacial carrier transfer and separation in heterojunction photocatalysts. In Z-scheme photocatalysts, the recombination of photogenerated electron-hole pairs is prevented so that the redox capacity is maintained. Here, one-dimensional graphitic carbon nitride (g-C₃N₄)/CoFe₂O₄ fibres were synthesised as a new type of magnetic Z-scheme visible-light photocatalyst. Compared with pure g-C₃N₄ and CoFe₂O₄, the prepared composite photocatalysts showed considerably improved performance for the photooxidative degradation of tetracycline and methylene blue. In particular, the photodegradation efficiency of the g-C₃N₄/CoFe₂O₄ fibres for methylene blue was approximately two and seven times those of g-C₃N₄ and CoFe₂O₄, respectively. The formation mechanism of the Z-scheme heterojunctions in the g-C₃N₄/CoFe₂O₄ fibres was investigated using photocurrent spectroscopy and electrochemical impedance spectroscopy. We proposed that one of the reasons for the improved photodegradation performance is that the charge transport path in one-dimensional materials enables efficient photoelectron and hole transfer. Furthermore, the internal electric field of the prepared Z-scheme photocatalyst enhanced visible-light absorption, which provided a barrier for photoelectron-hole pair recombination.

The preparation of hybrid silicon quantum dots by one-step synthesis for tetracycline detection and antibacterial applications

In this study, we prepared three different silicon quantum dots (SiQDs-1, SiQDs-2 and SiQDs-3) by hydrothermal synthesis with rose Bengal as the reducing agent and triacetoxy(methyl)silane and allyloxytrimethylsilane as silicon sources. The as-prepared SiQDs not only exhibited potent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) but also showed specific responses to tetracycline (TC). The minimum inhibitory concentrations (MICs) of SiQDs-1, SiQDs-2 and SiQDs-3 were 0.55 mg mL^-1, 0.47 mg mL^-1 and 0.39 mg mL^-1 against E. coli, respectively, and 0.45 mg mL^-1, 0.34 mg mL^-1 and 0.34 mg mL^-1 against S. aureus, respectively. By examining the morphologies of bacteria and generation of reactive oxygen species (ROS), we speculated that these SiQDs shrink the bacteria and even directly destroy the bacterial structural integrity through the production of singlet oxygen. In addition, the fluorescence quenching effectiveness of SiQDs-3 also showed a strong linear relationship with TC concentration in the range of 0-1.2 μM with a detection limit of 0.318 μM, as a result of the internal filtering effect. Together, SiQDs not only can be a candidate to treat resistant bacterial infections, but also may be applied in practical detection of TC.

The coexistence of copper ions and TC affected the binding ability and the reaction order between extracellular polymeric substances of aerobic granular sludge and exogenous substances

As a barrier against external toxic effects, extracellular polymeric substances (EPSs) directly affect the toxicity and removal efficiency of exogenous substances. The reaction of EPSs with exogenous substances has been taken into consideration. The contents of EPSs in sludge cultivated by different influent water vary greatly, which leads to great differences in the binding ability and reaction sequence between EPSs and exogenous substances. However, the results in this respect are very limited. In this study, the binding characteristics between exogenous tetracycline (TC)/copper ions (Cu²⁺) and EPSs from aerobic granular sludge cultured under single and coexisting TC/Cu²⁺ were assessed by three-dimensional fluorescence-parallel factor analysis. The pollutants in the influent water could directionally induce microorganisms to secrete more EPSs, while fluorescence substances in EPSs could combine with the exogenous substances to lessen their effects. In the presence of coexisting TC and Cu²⁺ in the influent water, the ability of fluorescence substances in EPSs to combine with exogenous TC or Cu²⁺ weakened, and humic substances in EPSs were more susceptible than protein substances to binding with exogenous substances. However, the reaction order between EPSs components and exogenous TC or Cu²⁺ was opposite, and the ability of fluorescence substances in EPSs to combine with exogenous TC or Cu²⁺ was enhanced under individual TC or Cu²⁺ existing in the influent water. This study provided new insights into the interaction between EPSs and exogenous substances.

Bibliometrics Analysis of Research Progress of Electrochemical Detection of Tetracycline Antibiotics

Tetracycline is a broad-spectrum class of antibiotics. The use of excessive doses of tetracycline antibiotics can result in their residues in food, posing varying degrees of risk to human health. Therefore, the establishment of a rapid and sensitive field detection method for tetracycline residues is of great practical importance to improve the safety of food-derived animal foods. Electrochemical analysis techniques are widely used in the field of pollutant detection because of the simple detection principle, easy operation of the instrument, and low cost of analysis. In this review, we summarize the electrochemical detection of tetracycline antibiotics by bibliometrics. Unlike the previously published reviews, this article reviews and analyzes the development of this topic. The contributions of different countries and different institutions were analyzed. Keyword analysis was used to explain the development of different research directions. The results of the analysis revealed that developments and innovations in materials science can enhance the performance of electrochemical detection of tetracycline antibiotics. Among them, gold nanoparticles and carbon nanotubes are the most used nanomaterials. Aptamer sensing strategies are the most favored methodologies in electrochemical detection of tetracycline antibiotics.

Multiresidues Multiclass Analytical Methods for Determination of Antibiotics in Animal Origin Food: A Critical Analysis

Veterinary drugs are widely used to prevent and treat diseases. The European Union has forbidden the use of antibiotics as growth promoters since 2006. Its abusive use leads to the presence of antibiotic residues (AR) in foods of animal origin which is associated with antibiotic resistance. The monitoring of AR in food intended for human consumption is of utmost importance to assure Food Safety. A systematic bibliographic review was carried out on the analytical methodologies, published in 2013, for the determination of AR in foods of animal origin. The food processing effect in the AR detected in animal products is also addressed. However, there is a preference for multiresidues multiclass methods, i.e., methodologies that allow determining simultaneously different classes of antibiotics, which is still a challenge for researchers. The wide diversity of physico-chemical properties of these drugs is an obstacle to achieving excellent analytical performance for a vast number of molecules analyzed concurrently. New techniques in sample preparation continue to be developed in order to obtain a compromise between good recoveries and extracts without interferences (clean extracts). The most widely used analytical methodology for the determination of AR is liquid chromatography coupled with mass spectrometry. However, the current trend is focused on the use of powerful high-resolution MS detectors such as Time of Flight and Orbitrap with modern chromatographic systems. Cooking time and temperature control are the key processing conditions influencing the reduction of AR in foods.

Research Advances in the Analysis of Estrogenic Endocrine Disrupting Compounds in Milk and Dairy Products

Milk and dairy products are sources of exposure to estrogenic endocrine disrupting compounds (e-EDCs). Estrogenic disruptors can accumulate in organisms through the food chain and may negatively affect ecosystems and organisms even at low concentrations. Therefore, the analysis of e-EDCs in dairy products is of practical significance. Continuous efforts have been made to establish effective methods to detect e-EDCs, using convenient sample pretreatments and simple steps. This review aims to summarize the recently reported pretreatment methods for estrogenic disruptors, such as solid-phase extraction (SPE) and liquid phase microextraction (LPME), determination methods including gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), Raman spectroscopy, and biosensors, to provide a reliable theoretical basis and operational method for e-EDC analysis in the future.

A ratiometric fluorescent sensor for tetracyclines detection in meat based on pH-dependence of targets with lanthanum-doped carbon dots as probes

Although some ratiometric fluorescent sensors have been reported to detect tetracyclines, most of ratiometric fluorescent sensors were established based on europium ion with a narrow linear range. In this work, a ratiometric fluorescent sensor for tetracyclines detection was established based on the dual-emission lanthanum-doped carbon dots (La-CDs) as probes combining with the characteristic pH-response of tetracyclines. The fluorescence intensity of tetracyclines will be enhanced in high pH, and the emission peak of tetracyclines overlapped with the peak of probes. The superposition effect of tetracyclines and probes at 515 nm greatly improved the sensitivity of the ratiometric fluorescent sensor and widened the detection range, and linear ranges for oxytetracycline (OTC) and tetracycline (TC) were respectively 0.00-805.20 μM and 0.00-1039.50 μM. Moreover, the preparation procedure of the La-CDs was simple and time saving and the coupling agent was not required. A comparison of La-CDs with undoped carbon dots (un-CDs) showed that the optical performance and sensing performance of La-CDs were improved. In addition, a portable paper sensor with La-CDs as probes was preliminarily explored in this work, and the sensor has been applied to detect OTC and TC in pork and fish with satisfactory results.

Carbon source type can affect tetracycline removal by Pseudomonas sp. TC952 through regulation of extracellular polymeric substances composition and production

The objective of this work is to elucidate the mechanism of tetracycline (TC) removal by Pseudomonas sp. TC952. The TC removal characteristics of strain TC952 under various environmental conditions were studied. Results showed that the bio-removal efficiency was significantly affected by initial TC and peptone concentration, pH values, divalent metal ion (Zn²⁺) and carbon source, and the strain TC952 efficiently removed approximately 72.8% of TC within 6 days with 10 g/L peptone. The best conditions for strain TC952 to remove TC are as follows: initial TC concentration is 50 mg/L, solution initial pH is 7, Zn²⁺ concentration is 0.1 μg/L, carbon source is peptone. And through intra- and extracellular fractions assay and extracellular polymeric substances (EPS) component analysis, TC removal by strain TC952 was mainly attributed to the adsorption by bacterial EPS and bacterial cell. Furthermore, different carbon source affected the EPS production content and component of strain TC952, so EPS produced under peptone and serine conditions could bio-adsorb TC and formed a buffer area outside the cells, thus reducing or preventing TC from entering the bacteria cells. All the results obtained showed that secretion of EPS and adsorption of TC by EPS and bacterial cell wall may be a common way for bacteria to reduce TC in the environment, which brought novel insights for better management of TC contamination by functional bacteria and for understanding the natural removal process of antibiotics by microorganisms in the environment.

Pyrazine Functionalization to Boost Antenna Effect in Rare-Earth Metal-Organic Frameworks for Tetracyclines Detection

Here we report a generalizable strategy for the synthesis of rare-earth metal-organic frameworks (RE-MOFs) with 12-connected RE9 clusters and shp-topology. A total of 26 isostructural RE-MOFs (JNU-205-RE and JNU-206-RE) were...

Graphene oxide-regulated low-background aptasensor for the "turn on" detection of tetracycline

Tetracyclines (TC) are a common antibiotic for using in livestock breeding and healthcare; however, due to the inappropriate application of TCs, more than 75% of TCs are excreted and released into the environment in an active form through human and animal urine and feces, which results in high levels of TCs in the ecological system, causing adverse effects on the food safety and human health. Thus, the high-performance monitoring of TC pollution is necessary. In this work, a highly sensitive fluorescent aptasensor was developed that was based on graphene oxide (GO) regulation of low background signal and target-induced fluorescence restoration. In the absence of analyte, the DNA probe (TC aptamer) was adsorbed completely by GO and failed to enhance the fluorescence of SYBR gold (SG), thereby resulting in a low background signal. When the TC-included samples were added, the DNA probe formed an aptamer-TC complex, thereby separating from the surface of the GO and inducing the fluorescence of SG. Under optimal conditions, the proposed strategy could detect TC concentrations of less than 6.2 × 10^-3 ng mL^-1, which is four orders of magnitude better than the detection limit of the "turn off" mode (53.9511 ng mL^-1). Moreover, this aptasensor has been used to detect TC from milk samples and wastewater samples, and its satisfactory performances demonstrate that the proposed strategy can be applied in practice for TC monitor in food safety and environmental protection. Therefore, we believe that this work is meaningful in pollution monitoring, environment restoration and emergency treatment.

Technological Advancements for the Detection of Antibiotics in Food Products

Antibiotics, nowadays, are not only used for the treatment of human diseases but also used in animal and poultry farming to increase production. Overuse of antibiotics leads to their circulation in the food chain due to unmanaged discharge. These circulating antibiotics and their residues are a major cause of antimicrobial resistance (AMR), so comprehensive and multifaceted measures aligning with the One Health approach are crucial to curb the emergence and dissemination of antibiotic resistance through the food chain. Different chromatographic techniques and capillary electrophoresis (CE) are being widely used for the separation and detection of antibiotics and their residues from food samples. However, the matrix present in food samples interferes with the proper detection of the antibiotics, which are present in trace concentrations. This review is focused on the scientific literature published in the last decade devoted to the detection of antibiotics in food products. Various extraction methods are employed for the enrichment of antibiotics from a wide variety of food samples; however, solid-phase extraction (SPE) techniques are often used for the extraction of antibiotics from food products and biological samples. In addition, this review has scrutinized how changing instrumental composition, organization, and working parameters in the chromatography and CE can greatly impact the identification and quantification of antibiotic residues. This review also summarized recent advancements in other detection methods such as immunological assays, surface-enhanced Raman spectroscopy (SERS)-based assays, and biosensors which have emerged as rapid, sensitive, and selective tools for accurate detection and quantification of traces of antibiotics.

Flow Injection Techniques for Tetracycline Quantification: A Review

The multiple therapeutic potentials of tetracycline and its worldwide usage have encouraged researchers to develop various methods for its assay in various matrices and for different purposes. In this regard, different analytical techniques have been exploited. Among those techniques is flow injection (FI), which is an extended family of three generations and five versions. The current manuscript reviews the utilization of FI techniques for developing assay methods for tetracycline. The review covers more than forty methods, since the inception of FI techniques and up to date. The review highlights the advantages of the application of FI techniques for quantification of tetracycline in terms of reagent consumption, sample frequency, accuracy, and practitioner safety, besides instrumentation simplicity and cost-effectiveness. The review also addresses applications to several matrices ranging from simple matrices such as standard solutions and pharmaceutical formulations to complex matrices such as biological fluids and food. Prior to the review, a brief background on the principles and developments of FI techniques is illustrated.

The survival and removal mechanism of Sphingobacterium changzhouense TC931 under tetracycline stress and its' ecological safety after application

Sphingobacterium changzhouense TC931 was isolated as a novel TC (tetracycline) removal bacterium through adsorption on extracellular polymerase substances (EPS) and cellular surface and biodegradation. TC biodegradation efficiency by strain TC931 was affected by solution initial pH and carbon source. Polysaccharides and hydrocarbons in EPS and cellular surface were responsible for TC biosorption. Eight possible biodegradation products were identified and the biodegradation pathway was proposed. Strain TC931 was rich in antibiotic resistance genes, and tetX_-TC931 and antibiotics resistance genome island (GI) may be acquired via horizontal gene transfer in early evolutionary history. The GI was incomplete and may stable in strain TC931, but it could develop into an intact and transferability GI with help of other mobile genetic elements. This work offers a theoretical basis for understanding the survival and biodegradation mechanisms of S. changzhouense TC931 under TC stress, and offers an ecological safety assessment for its application in environmental bioremediation.

Determination of Six Tetracyclines in Eggs and Chicken by Dispersive Liquid-Liquid Microextraction Combined with High-Performance Liquid Chromatography

BACKGROUND

The wide livestock usage of tetracyclines may result in drug residues in foods. Therefore, it is necessary to develop reliable methods for the determination of tetracyclines in foods.

OBJECTIVE

A dispersive liquid-liquid microextraction (DLLME) combined with high-performance liquid chromatography (HPLC) method was developed for the analysis of six tetracyclines in eggs and chicken.

METHODS

After deproteinization, tetracyclines in acidic solutions were concentrated by vortex-assisted DLLME. Followed by the addition of NaCl (35% for eggs and 20% for chicken), a mixture of ionic liquid [Bmim]PF6 and ethyl acetate (300 μL-50 μL for eggs and 200 μL-60 μL for chicken) was used as the extractant. After centrifugation, the extract was collected for HPLC analysis.

RESULTS

The developed method showed good linear relationship (10.0-500 μg/kg), low method detection limits (0.219-1.42 μg/kg) and quantification limits (0.731-4.72 μg/kg), satisfactory relative recoveries (87.1-104%) with intra-day and inter-day RSDs in the ranges of 0.853-8.62% and 1.65-11.8%, respectively. The established method was successfully applied for the determination of six tetracyclines in eggs and chicken of different parts. The contents of tetracyclines in all samples were lower than their maximum residue limits.

CONCLUSIONS

A DLLME-HPLC method has been developed for the analysis of six tetracyclines in animal derived foods using ionic liquid and ethyl acetate as the extractant.

HIGHLIGHTS

The developed method is simple, sensitive, cost-effective and has strong anti-interference ability. This method has been successfully applied to the analysis of six tetracyclines in eggs and chicken.

Determination of tetracycline, oxytetracycline and chlortetracycline residues in seafood products of Saudi Arabia using high performance liquid chromatography-Photo diode array detection

Residues of oxytetracycline, tetracycline and chlortetracycline in seafood products of Saudi Arabia were detected by using a simple, sensitive and rapid method via HPLC-PDA. The protein precipitation method that was used for sample extraction demonstrated high recoveries of OTC, TC and CTC. The limits of detection were 0.015 µg/g and 0.025,0.062 µg/g for all TCs in fish and shellfish, respectively. The limits of quantitation were 0.125 µg/g and 0.175 µg/g for all TCs in fish and shellfish, respectively. The method was precise and accurate since the RSD was less than 2%, while the % recovery was 95-105%. This study determined the occurrence of OTC, TC and CTC in seafood products that are sold in KSA's markets. The overall occurrence of these three medications in 249 seafood products was 24%(n = 60), while 15%(n = 37) exceeded the MRL. Thus, our recommendations are to enhance the monitoring of food production prior to marketing and to educate people regarding the proper disposal of antibiotics.

Determination of seven tetracyclines in milk by dissolvable layered double hydroxide-based solid-phase extraction coupled with high-performance liquid chromatography

A dissolvable layered double hydroxide-based solid-phase extraction combined with high-performance liquid chromatography was developed for the analysis of minocycline, oxytetracycline, tetracycline, demeclocycline, metacycline, chlortetracycline and doxycycline in milk samples. In situ formation of the layered double hydroxide was achieved by the addition of MgCl₂-AlCl₃ solution to alkaline deproteinized milk. The analytes were efficiently extracted by the Mg/Al layered double hydroxide. After centrifugation, the co-precipitates were dissolved in 0.1 mol L^-1 Na₂EDTA-McIlvaine buffer prior to HPLC analysis. Under optimized conditions, the method achieved low detection limits of 0.414-0.986 μg L^-1 and quantification limits of 1.38-3.29 μg L^-1, and good recoveries of 93.5-100% with intra- and inter-day RSDs of 0.498-4.08% and 1.23-10.0%, respectively. This method is convenient, accurate, sensitive, rapid, cost-effective, eco-friendly, and suitable for the determination of seven tetracycline antibiotics in milk samples.

Development of a surfactant-assisted dispersive solid phase extraction using deep eutectic solvent to extract four tetracycline antibiotics residues in milk samples

In this study, a new floating dispersive solid phase extraction method based on deep eutectic solvents has been developed in a home-made extraction device for the extraction of four tetracycline antibiotics from milk samples. In this approach, the sorbent (activated carbon) was dispersed in whole parts of solution with the aid of air stream and floated on top of the solution with the aid of the surfactant (lauryl betaine) and air bubbles. After collection of the sorbent, the adsorbed analytes were eluted with tetrabutyl ammonium chloride-propionic acid deep eutectic solvent under sonication. In this method, there was no need of organic dispersive and extraction solvents and the used sorbent was collected on top of the solution and collected without centrifugation. The validation parameters showed that low limits of detection (0.1-0.3 μg/kg) and quantification (0.6-1.0 μg/kg), acceptable enrichment factors (52-60), efficient extraction recoveries (80-91%), and satisfactory relative standard deviations (≤9.8%) were obtained. Eventually, the method was successfully applied on different milk samples and tetracycline was determined in them.

Monitoring of residual antibacterial agents in animal and fishery products in Tokyo from 2003 to 2019: application and verification of a screening strategy based on microbiological methods

Residual antibacterial agents in 5909 animal and fishery products in Tokyo, Japan, were investigated over 17 consecutive years (2003-2019). Monitoring of 32 antibacterial agents (lincosamides, macrolides, penicillins, quinorones and tetracyclines) per product was accomplished via two steps: screening (by microbiological methods) and confirmation (by instrumental methods). Microbiological screening methods identified presumptive groups and determined semi-quantitative values. The instrumental methods quantified 81 residues of 11 different antibacterial agents in 72 samples. The screening strategy based on microbiological methods demonstrated the following: (i) the majority of the samples (over 99%) met Japanese regulations, (ii) using multiple methods provided a reliable inspection system with accurate quantitative values and (iii) there was a constant presence of tetracyclines and unexpected residues (lincomycin and norfloxacin) in various products. Thus, this long-term monitoring and screening strategy provided evidence that the frequencies and trends of residual antibacterial agents not only enhance food safety but also help to prevent antimicrobial resistance.

Fabric Phase Sorptive Extraction of Selected Steroid Hormone Residues in Commercial Raw Milk Followed by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

Hormones in edible matrices, such as milk, are a subject of concern because of their adverse effects on the endocrine system and cell signaling and the consequent disruption of homeostasis in human consumers. Therefore, the assessment of the presence of hormones in milk as potential endocrine-disrupting compounds is warranted. However, the complexity of milk as a sample matrix and the ultra-low concentration of hormones pose significant analytical challenges. Fabric phase sorptive extraction (FPSE) has emerged as a powerful analytical technique for the extraction of emerging pollutants from complex aqueous matrices. FPSE allows for substantially simplified sample handling and short extraction and desorption times, as well as the decreased use of organic solvents. It is considered a green alternative to traditional extraction methodologies. In this work, the FPSE technique was evaluated to perform the simultaneous extraction of 15 steroid hormones from raw milk without employing any sample pretreatment steps. Clean and preconcentrated hormone solutions obtained from FPSE of raw milk were analyzed using ultra-high-performance liquid chromatography–tandem mass spectrometry to achieve low detection limits, which ranged from 0.047 to 1.242 ng·mL⁻¹. Because of the presence of many interferents in milk, such as proteins, lipids, and sugar, the effect of fat content on the extraction procedure was also thoroughly studied. Additionally, for the first time, the effect of lactose on the extraction of steroid hormones was evaluated, and the results showed that the extraction efficiencies were enhanced in lactose-free samples. Finally, the optimized methodology was applied to commercial samples of cow and goat milk, and no measurable concentrations of the studied hormones were detected in these samples.

Development and perspectives of rapid detection technology in food and environment

Food safety become a hot issue currently with globalization of food trade and food supply chains. Chemical pollution, microbial contamination and adulteration in food have attracted more attention worldwide. Contamination with antibiotics, estrogens and heavy metals in water environment and soil environment have also turn into an enormous threat to food safety. Traditional small-scale, long-term detection technologies have been unable to meet the current needs. In the monitoring process, rapid, convenient, accurate analysis and detection technologies have become the future development trend. We critically synthesizing the current knowledge of various rapid detection technology, and briefly touched upon the problem which still exist in research process. The review showed that the application of novel materials promotes the development of rapid detection technology, high-throughput and portability would be popular study directions in the future. Of course, the ultimate aim of the research is how to industrialization these technologies and apply to the market.

Determination of antibiotics in meat samples using analytical methodologies: A review

Antibiotics are widely used to prevent or treat some diseases in human and veterinary medicine and also as animal growth promoters. The presence of these compounds in foods derived from food-producing animals can be a risk for human health. Consequently, regulatory agencies have set maximum residue limits for antibiotics in food samples. Therefore, the development of novel methodologies for its determination in food samples is required. Specifically, the analysis and quantification of these substances in meat tissues is a challenge for the analytical chemistry research community. This is due to the complexity of the matrix and the low detection limits required by the regulatory agencies. In this sense, a comprehensive review on the development of new sample preparation treatments involving extraction, cleanup, and enrichment steps of antibiotics in meat samples in combination with sensitive and sophisticated determination techniques that have been carry out in the last years is necessary. Therefore, the aim of this work is to summarize the published methodologies for the determination of antibiotics from 2016 until the beginning of the second semester of 2020. The first part of this review includes an introduction about antibiotic families, followed by sample preparation and determination techniques applied to the different families. Finally, a detailed discussion of the current trends and the future possible perspectives in this field are also included.