Monitoring the presence of residues of tetracyclines in baby food samples by HPLC-MS/MS

A self-calibrating ratiometric fluorescence sensor with photonic crystal-based signal amplification for the detection of tetracycline in food

A dual-color ratiometric fluorescence sensor based on photonic crystals (PCs) was developed to detect tetracycline (TC) in food. PC was fabricated via self-assembly of carbon dots (CDs)-loaded SiO2 nanoparticles. Gold nanoclusters (AuNCs) and copper ions (Cu2+) were then adsorbed onto the PC for sensor fabrication. The fluorescence of AuNCs was amplified by the PC with an enhancement ratio of 7.6, providing higher sensitivity. The fluorescence of AuNCs was quenched by Cu2+, whereas that of CDs remained unchanged as an internal reference. TC restored the fluorescence of AuNCs owing to its complexation with Cu2+, resulting in a change in the fluorescence intensity ratio. The sensor exhibited a good linear relationship with TC concentrations ranging from 0.1 to 10 μM, with a detection limit of 34 nM. Furthermore, the sensor was applied for TC detection in food with satisfactory recoveries and relative standard deviations, revealing great potential in practical application.

A novel fluorescence platform for specific detection of tetracycline antibiotics based on [MQDA-Eu3+] system

Tetracycline antibiotics (TCs) are extensively used in clinical medicine, animal husbandry, and aquaculture because of their cost-effectiveness and high antibacterial efficacy. However, the presence of TCs residues in the environment poses risks to humans. In this study, an inner filter effect (IFE) fluorescent probe, 2,2'-(ethane-1,2-diylbis((2-((2-methylquinolin-8-yl)amino)-2-oxoethyl)azanediyl))diacetic acid (MQDA), was developed for the rapid detection of Eu3+ within 30 s. And its complex [MQDA-Eu3+] was successfully used for the detection of TCs. Upon coordination of a carboxyl of MQDA with Eu3+ to form a [MQDA-Eu3+] complex, the carboxyl served as an antenna ligand for the effective detection of Eu3+ to intensify the emission intensity of MQDA via "antenna effect", the process was the energy absorbed by TCs via UV excitation was effectively transferred to Eu3+. Fluorescence quenching of the [MQDA-Eu3+] complex was caused by the IFE in multicolor fluorescence systems. The limits of detection of [MQDA-Eu3+] for oxytetracycline, chlorotetracycline hydrochloride, and tetracycline were 0.80, 0.93, and 1.7 μM in DMSO/HEPES (7:3, v/v, pH = 7.0), respectively. [MQDA-Eu3+] demonstrated sensitive detection of TCs in environmental and food samples with satisfactory recoveries and exhibited excellent imaging capabilities for TCs in living cells and zebrafish with low cytotoxicity. The proposed approach demonstrated considerable potential for the quantitative detection of TCs.

Rapid Determination of Tetracyclines in Drinking and Environmental Waters Using Fully Automatic Solid-Phase Extraction with Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry

The abuse and irrational use of tetracyclines (TCs) in human medicine and animal husbandry has become a serious concern, affecting the ecological environment and human health. The aim of this study was to develop a sensitive and selective method using fully automatic solid-phase extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry for the determination of twelve TCs in water. Four isotope-labeled internal standards for TCs were used to correct matrix effects. Several parameters affecting extraction efficiency were systematically optimized, and the optimum experimental conditions found were 1.0 L water sample with 0.5 g/L Na2EDTA (pH 3.0) extracted and enriched by CNW HLB cartridge and eluted by 4 mL of acetone:methanol (v/v, 1:1). The enrichment factors were up to 798-1059 but only requiring about 60 min per six samples. Under the optimized conditions, the linearity of the method ranged from 0.2 to 100 μg/L for 12 TCs, the detection limits were as low as 0.01-0.15 ng/L, and the recoveries were in the range of 70%-118%, with relative standard deviations less than 15%. The developed method can be successfully utilized for the determination of 12 TCs in pure water, tap water, river water, and mariculture seawater. In summary, three and six TCs were detected in river water and mariculture seawater, respectively, with total concentrations of 0.074-0.520 ng/L (mean 0.248 ng/L) and 0.792-58.369 ng/L (12.629 ng/L), respectively. Tetracycline (TC) and oxytetracycline (OTC) were the dominant TCs in river water, while doxytetracycline (DXC) and OTC were dominant in mariculture seawater.

From field to table: Ensuring food safety by reducing pesticide residues in food

The present review addresses the significance of lowering pesticide residue levels in food items because of their harmful impacts on human health, wildlife populations, and the environment. It draws attention to the possible health risks-acute and chronic poisoning, cancer, unfavorable effects on reproduction, and harm to the brain or immunological systems-that come with pesticide exposure. Numerous traditional and cutting-edge methods, such as washing, blanching, peeling, thermal treatments, alkaline electrolyzed water washing, cold plasma, ultrasonic cleaning, ozone treatment, and enzymatic treatment, have been proposed to reduce pesticide residues in food products. It highlights the necessity of a paradigm change in crop protection and agri-food production on a global scale. It offers opportunities to guarantee food safety through the mitigation of pesticide residues in food. The review concludes that the first step in reducing worries about the negative effects of pesticides is to implement regulatory measures to regulate their use. In order to lower the exposure to dietary pesticides, the present review also emphasizes the significance of precision agricultural practices and integrated pest management techniques. The advanced approaches covered in this review present viable options along with traditional methods and possess the potential to lower pesticide residues in food items without sacrificing quality. It can be concluded from the present review that a paradigm shift towards sustainable agriculture and food production is essential to minimize pesticide residues in food, safeguarding human health, wildlife populations, and the environment. Furthermore, there is a need to refine the conventional methods of pesticide removal from food items along with the development of modern techniques.

Pyrene and Eu3+ modified mesoporous silica used as a fluorescent probe for ratiometric detection of tetracycline antibiotics

The detection of residual tetracycline antibiotics (TCs) in the aquatic environment is important because of the irreversible damage of TCs to the ecosystem and human health. Considering the photostability, sensitivity, and accuracy of the detection systems, mesoporous SBA-15 silica material was an ideal support matrix for improving photostability because it can protect the optical properties of fluorescent signals. To achieve ratiometric detection (with sensitivity and accuracy), pyrene and Eu3+ as two fluorescent signals were implemented into SBA-15, and an organic-inorganic hybrid fluorescent nanoprobe Py/EDTA-SBA-15@Eu3+ was constructed. In the presence of TCs, the red emission of Eu3+ in the nanoprobe was sensitized, and the fluorescence resonance energy transfer occurred from pyrene to Eu3+, resulting in the increased emission of Eu3+ at 617 nm and the decreased emission of pyrene at 384 nm. By monitoring the fluorescent intensity changes at 617 and 384 nm (F617/F384), the nanoprobe achieved the ratiometric detection of oxytetracycline (OTC) and tetracycline (TC) in the range of 0.20-80 and 0.40-80 μM, respectively, with detection limits of 0.18 nM for OTC and 5.83 nM for TC. In addition, the practical application of the nanoprobe was validated in tap water and honey samples.

A water-stabilized Tb-MOF can be used as a sensitive and selective fluorescence sensor for the detection of oxytetracycline hydrochloride

Oxytetracycline hydrochloride (OTC) is a commonly used over-the-counter antibiotic, valued for its potent antibacterial properties. However, the inappropriate and excessive use of OTC can result in the accumulation of the drug in both the environment and human body, causing significant harm to ecosystems and human health. Therefore, the development of a fast and sensitive method for detecting OTC is of great significance. Lanthanide metal-organic frameworks (LnMOFs) can effectively excite lanthanide metals to emit long-lifetime, narrow and stable fluorescence based on the antenna effect, but their application in fluorescence sensing is rarely reported. In this work, a strongly fluorescent material Tb-MOF was synthesized by a facile solvothermal method using 1,2,4,5-phenylenetetracarboxylic acid (H4btec) and 1,10-phenanthroline (1,10-phen) as organic ligands and lanthanide metal Tb as the luminescent center. Tb-MOF is a stable material in water and shows excellent linearity with OTC in the concentration range of 0 ∼ 70 μM, with low detection limit (0.12 μM) and luminescence color transition from bright green to dark green during the detection process. X-ray diffraction, UV-vis absorption and fluorescence lifetime analyses revealed that the fluorescence quenching of Tb-MOF by OTC is caused by the inner filter effect in static quenching. Test strips for OTC detection were successfully prepared using Tb-MOF. These strips are not only low cost and easy to prepare but can also be used as portable sensing devices that can be easily distinguished by the naked eye during OTC testing. This study not only presents a fluorescent probe for the detection of OTC in water but also offers a practical method for converting fluorescent luminescent materials into functional devices for OTC detection.

Selective Antibody-Free Sensing Membranes for Picogram Tetracycline Detection

As an antibody-free sensing membrane for the detection of the antibiotic tetracycline (TC), a liquid PVC membrane doped with the ion-pair tetracycline/θ-shaped anion [3,3'-Co(1,2-C₂B₉H₁₁)₂]^- ([o-COSAN]^-) was formulated and deposited on a SWCNT modified gold microelectrode. The chosen transduction technique was electrochemical impedance spectroscopy (EIS). The PVC membrane was composed of: the tetracycline/[o-COSAN]^- ion-pair, a plasticizer. A detection limit of 0.3 pg/L was obtained with this membrane, using bis(2-ethylhexyl) sebacate as a plasticizer. The sensitivity of detection of tetracycline was five times higher than that of oxytetracycline and of terramycin, and 22 times higher than that of demeclocycline. A shelf-life of the prepared sensor was more than six months and was used for detection in spiked honey samples. These results open the way to having continuous monitoring sensors with a high detection capacity, are easy to clean, avoid the use of antibodies, and produce a direct measurement.

Identification and Quantification of 29 Active Substances by HPLC-ESI-MS/MS in Lyophilized Swine Manure Samples

Veterinary drugs are frequently employed to treat and prevent diseases in food-producing animals to improve animal health and to avoid the introduction of microorganisms into the food chain. The analysis of the presence of pharmaceutical residues in animal manure could help to evaluate the legal and illegal practices during food production without harming the animals and to correctly manage manure when it is going to be applied as a fertilizer. This article describes a method for the simultaneous analysis of 29 active substances, mostly antibiotics and antiparasitic agents. Substances were extracted from lyophilized manure with a methanol:McIlvaine solution and analyzed with HPLC-ESI-MS/MS and a C18 HPLC column. The method was validated following European guidelines, the achieved trueness was between 63 and 128% (depending on the analytes), and the linearity was between 100 and 1500 µg/kg. The applicability of the method was demonstrated in 40 manure samples collected from pig farms where tetracycline was quantified in 7.5% of the samples. These results show the viability of this non-invasive method for the control of the legal and illegal administration of pharmaceuticals in food-producing animals.

A fluorescent and scattering dual-mode probe based on a carbon dot@cerium-guanosine monophosphate coordination polymer network for tetracycline detection

Dual-mode sensing with a two-signal read-out is conducive to the improvement of detection accuracy. Herein, a fluorescent and scattering dual-mode chemosensor for tetracycline (TC) is proposed based on a carbon dot@cerium-guanosine monophosphate (CD@GMP-Ce) coordination polymer network. The inexpensive CD@GMP-Ce was prepared by exploiting the adaptive inclusion capability of coordination polymers and possessed remarkable fluorescence and strong Rayleigh scattering. The functional CD@GMP-Ce demonstrated fluorescence and scattering, the two optical-signal responses to TC simultaneously. Based on TC-specific fluorescence and scattering decline, the dual-mode detection of TC was established and the probe's detection limits were 43 nM in the fluorescence mode and 77 nM in the scattering mode, respectively. Furthermore, the potential application of the dual-mode sensor was verified by measuring TC in milk and tap-water samples. The study not only provides a new perspective for the development of assay methods for TC but also expands the applications of cerium coordination polymers.

Tetracycline biotransformation by a novel bacterial strain Alcaligenes sp. T17

Comprehensive knowledge on the biotransformation of tetracycline (TC) is critical for the improvement of TC removal in the bioremediation process. This work isolated a novel TC-degrading bacterial strain Alcaligenes sp. T17 and explored its degradation ability under different conditions. Temperature and pH could affect the degradation efficiency, and higher temperature as well as neutral and weakly acidic conditions were conducive to the biotransformation. Response surface methodology predicted the maximum degradation rate of TC (94.35%) under the condition of 25.15 mg/L TC, pH 7.23, and inoculation dosage 1.17% at 40 °C. According to the result of disk diffusion tests, the biodegradation products had lower antimicrobial potency than the parent compound. Five potential biodegradation products were identified, and a possible degradation pathway (degrouping, oxidation and ring-opening) was proposed. The draft genome of strain T17 was also determined. Genomic analysis indicated that strain T17 harbored multiple genes that participated in the metabolism of aromatic compounds as well as genes encoding oxygenases. These functional genes may be relevant to TC biotransformation. This study could provide new insights towards the biotransformation of TC mediated by bacteria.

A comprehensive review on biodegradation of tetracyclines: Current research progress and prospect

The release of tetracyclines (TCs) in the environment is of significant concern because the residual antibiotics may promote resistance in pathogenic microorganisms, and the transfer of antibiotic resistance genes poses a potential threat to ecosystems. Microbial biodegradation plays an important role in removing TCs in both natural and artificial systems. After long-term acclimation, microorganisms that can tolerate and degrade TCs are retained to achieve efficient removal of TCs under the optimum conditions (e.g. optimal operational parameters and moderate concentrations of TCs). To date, cultivation-based techniques have been used to isolate bacteria or fungi with potential degradation ability. Moreover, the biodegradation mechanism of TCs can be unveiled with the development of chemical analysis (e.g. UPLC-Q-TOF mass spectrometer) and molecular biology techniques (e.g. 16S rRNA gene sequencing, multi-omics sequencing, and whole genome sequencing). In this review, we made an overview of the biodegradation of TCs in different systems, refined functional microbial communities and pure isolates relevant to TCs biodegradation, and summarized the biodegradation products, pathways, and degradation genes of TCs. In addition, ecological risks of TCs biodegradation were considered from the perspectives of metabolic products toxicity and resistance genes. Overall, this article aimed to outline the research progress of TCs biodegradation and propose future research prospects.

A dual-signal fluorescent sensor based on MoS2 and CdTe quantum dots for tetracycline detection in milk

A dual-signal fluorescent sensor was developed for tetracycline (TET) detection in milk with excellent reproducibility and stability. In this protocol, molybdenum disulfide quantum dots (MoS₂ QDs) with blue fluorescence and cadmium telluride quantum dots (CdTe QDs) with yellow fluorescence were synthesized to establish the MoS₂/CdTe-based sensor with two fluorescence emission peaks at 433 nm and 573 nm. With the addition of TET, the fluorescence of MoS₂/CdTe were quenched by photoinduced electron transfer (PET), and the fluorescence of CdTe QDs were quenched more obvious than MoS₂ QDs. With the strategy, a calibration curve was established between the TET concentration in the range of 0.1-1 μM and the ratio of fluorescence intensity at 573 nm and 433 nm (F₅₇₃/F₄₃₃). Furthermore, the dual-signal sensor was applied for TET detection in milk samples with the recovery of 95.53-104.22% and the relative standard deviation (RSD) less than 5%, indicating the strong application potential.

Determination of Arsenic(III) and Total Arsenic at Trace Levels in Baby Food Samples via a New Functionalized Magnetic Graphane Oxide Nanocomposite

Baby food safety is an essential issue in health policy. For this reason, a simple, cheap, and fast analytical procedure to developed arsenic(III) and total arsenic determination in baby food samples using functionalized magnetic graphane oxide nanocomposite. A new nanocomposite anchored of tiopronin (TSH) magnetic graphane oxide (GO-PG4@Fe₃O₄-TSH) was first synthesized/characterized and used as an adsorbent to determine arsenic(III) and total arsenic for baby food samples. Arsenic(III) was directly determined on GO-PG4@Fe₃O₄-TSH nanocomposite at pH 4.5. The determination of total arsenic used KI and L( +) ascorbic acid solution as reducing reagents. The parameters influential on arsenic(III) determination in the baby food samples including the sample's pH, adsorption time, amount of GO-PG4@Fe₃O₄-TSH, eluent type, sample volume, reducing reagent type and amount, and also foreign ion effect were investigated. The GO-PG4@Fe₃O₄-TSH carrying As(III) could easily be separated from baby food samples via applying an external magnetic field. The detection limit for arsenic(III) was found as 0.11 μg L^-1, while the limit of quantification values was computed as 0.37 μg L^-1. The precision of results, expressed as relative standard deviation, was always lower than 1.6% at 1 mg L^-1 As(III) levels. The accuracy of this method was confirmed by analysis of certified reference material. The method was successively applied to determine arsenic(III) and total arsenic in baby food samples.

Europium Doped Silicon Quantum Dot As a Novel FRET Based Dual Detection Probe: Sensitive Detection of Tetracycline, Zinc, and Cadmium

The imbalance of Zn²⁺ /Cd²⁺ in the human body can lead to many serious diseases due to the overuse of antibiotics and deposition in animal products. Developing a functional material for detecting is challenging and in demand. Herein, silicon quantum dots (SiQDs) are designed as a functional platform for the detection of tetracycline and Zn²⁺ /Cd²⁺ . The COOH functionalized SiQDs with the emission wavelength of 450 nm are chelated with Eu(NO₃ )₃ to form SiQDs-Eu³⁺ ratio fluorescent probes, which can be used to detect tetracycline (TCs) and Zn²⁺ /Cd²⁺ by fluorescence resonance energy transfer (FRET) principle sequentially. The fluorescent probe showed good linearity between ion concentration and fluorescence enhancement. The detection limit of TCs and Zn²⁺ /Cd²⁺ are 0.2 × 10^-6  m and 3 × 10^-6  m, respectively, when the pH of the solution is 7.4. In addition, the synthesized SiQDs-Eu³⁺ exhibited good stability (from 94.9% to 103.1%). The relative standard deviations (RSD, n = 10) of human serum and urine were both less than 3%. Therefore, the SiQDs-Eu³⁺ ratio fluorescence probe will provide a good application prospect in actual sample detection.

Microbial and chemical pollutants on the manure-crops pathway in the perspective of "One Health" holistic approach

This study determined the impact of poultry and bovine manure fertilization on the content of antibiotics, heavy metals (HMs), and the quantitative and qualitative composition of integrase and antibiotic resistance genes in soil, groundwater, and crops cultivated on manure-amended plots. Antibiotic concentration levels were analyzed using the HPLC-MS/MS, heavy metal concentration level were measured by HGAAS and ICP-OES, while the integrase genes and ARGs were quantified using Real-Time PCR (qPCR) method. Manure, soil, and crops samples contained the highest concentration of Zn (10⁴-10⁵ ng g_dm^-1) and Cu (10³-10⁵ ng g_dm^-1) of all HMs tested. Manure-supplemented soil was characterised by a high concentration of doxycycline and enrofloxacin. A high abundance of integrase genes was noted in samples of manure (10⁹-10¹⁰ copies g_dm^-1) and soil (10⁷-10⁸ copies g_dm^-1). Among all the analyzed genes, sul1, sul2, bla_TEM, and integrase genes were the most common. Results of the study demonstrate the selective character of ARGs transfer from poultry and bovine manure to plants. The only gene to occur in all studied environmental compartments was sul1 (from 10² - groundwater to 10¹¹ - poultry manure). It was also found that animal manure may cause an increase in the HMs concentration in soil and their accumulation in crops, which may influence the health of humans and animals consuming crops grown on manure-amended soil. The high abundance of integrase genes and ARGs and their reciprocal correlations with HMs pose a serious risk of the rapid spread of antibiotic resistance in the environment. Moreover, unusual dependencies between integrase genes and selected ARGs indicate the possibility of changes in the mobility nature of genetic elements.

Ratiometric fluorescent probe for tetracycline detection based on waste printing paper

Tetracycline (TC) is a broad-spectrum antibiotic used to treat bacterial infections. In this study, a ratiometric fluorescence (FL) probe was developed to detect TC in water samples using waste printing paper extract as a FL indicator. For this ratiometric probe, the emission of printing paper extract at 436 nm gradually decreased and the emission of a mixed solution at 538 nm significantly increased with the sequential addition of TC upon excitation at 390 nm, coupled with a marked FL colour change from bright blue to faint yellow. Therefore, a ratiometric F₅₃₈ /F₄₃₆ FL probe was created for TC detection by simply mixing the printing paper extraction and TC. Under the optimized conditions, a linear range from 1 to 100 μM and a detection limit of 0.48 μM (S/N = 3) for TC were obtained. Importantly, the FL probe can be easily prepared with rapid response, high sensitivity, and good selectivity. The application of waste printing paper extract for detection of TC in environmental water samples was demonstrated.

[Research progress of microextraction by packed sorbent and its application in microvolume sample extraction]

Microextraction is a rapidly developing sample preparation technology in the field of analytical chemistry, which is seeing widespread application. Accurate sample preparation can not only save time but also improve the efficiency of analysis, determination, and data quality. At present, sample pretreatment methods must be rapid, allow for miniaturization, automation, and convenient online connection with analytical instruments. To meet the requirements of green analytical methods and improve the extraction efficiency, microextraction techniques have been introduced as suitable replacements to conventional sample preparation and extraction methods. Microextraction using a packed sorbent (MEPS) is a new type of sample preparation technology. The MEPS equipment was prepared using microsyringe with a volume of 50-500 μL, including MEPS syringes and MEPS adsorption beds (barrel insert and needle, BIN), which is essentially similar to a miniaturized solid phase extraction device. The BIN contains the adsorbent and is built into the syringe needle. A typical MEPS extraction procedure involves repeatedly pumping the sample solution in two directions (up and down) through the adsorbent multiple times in the MEPS syringe. The specific operation course of MEPS includes conditioning, loading, washing, elution, and introduction into the analysis instrument. The conditioning process is adopted to infiltrate the dry sorbent and remove bubbles between the filler particles. The adsorption process is accomplished by pulling the liquid plunger of the syringe so that the sample flows through the adsorbent in both directions multiple times. The washing process involves rinsing the sorbent to remove unwanted components after the analyte is retained. The elution process involves the use of an eluent to ensure that the sample flows through the adsorbent in both directions multiple times, so that elution can be realized by the pumping-pushing action. The target analyte is eluted with the eluent, which can be directly used for chromatographic analysis. However, when processing complex biological matrix samples by MEPS, pretreatment steps such as dilution of the sample and removal of proteins are commonly required. At present, the operation modes of the MEPS equipment are classified into three types: manual, semi-automated, and fully automated. This increase in the degree of automation is highly conducive to processing extremely low or extremely high sample volumes. Critical factors affecting the MEPS performance have been investigated in this study. The conditions for MEPS optimization are the operating process parameters, including sample flow rate, sample volume, number of sample extraction cycles, type and volume of the adsorbent, and elution solvents. It is also necessary to consider the effect of the sample matrix on the performance of MEPS. The MEPS sorbent should be cleaned by a solvent to eliminate carryover and reuse. The sorbent is a core aspect of MEPS. Several types of commercial and non-commercial sorbents have been used in MEPS. Commercial sorbents include silica-based sorbents such as unmodified silica (SIL), C2, C8, and C18. Unmodified silicon-based silica is a normal phase adsorption material, which is highly polar and can be used to retain polar analytes. C18, C8, and C2 materials are suitable for reversed-phase adsorption, while SCX, SAX, APS, and M1 (C8+SCX) adsorbents are suitable for the mixed-mode and ion-exchange modes. Noncommercial sorbents include molecularly imprinted materials, restricted-access molecularly imprinted materials, graphitized carbon, conductive polymer materials, modified silicon materials, and covalent-organic framework materials. The performance of MEPS has recently been illustrated by online with LC-MS and GC-MS assays for the analysis of biological matrices, environmental samples, and food samples. Pretreatment in MEPS protocols includes dilution, protein precipitation, and centrifugation in biological fluid matrices. Because of the small sample size, fast operation, etc., MEPS is expected to be more widely used in the analysis of bio-matrix samples. MEPS devices could also play an important role in field pretreatment and analysis.

Development and validation of an LC-MS/MS screening method for macrolide and quinolone residues in baby food

A simple, rapid and sensitive screening method by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the identification of 7 macrolides (clarithromycin, erythromycin, oleandomycin, spiramycin, tilmicosin, troleandomycin and tylosin) and 8 quinolones (ciprofloxacin, difloxacin, enrofloxacin, flumequine, moxifloxacin, nalidixic acid, norfloxacin and ofloxacin) in meat and egg-based baby foods. Sample preparation was performed using an alkaline modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) extraction method without additional clean-up steps. A simplex-lattice mixture experimental design was used in the optimization of the QuEChERS extraction solvent. The developed method was successfully validated according to the Commission Decision 2002/657/EC and the European Community Reference Laboratories Residues Guidelines regarding the validation of screening methods 20/01/2010, adopting a fixed permited tolerance for relative ion ratio. Samples of baby food (n = 44) commercialized in Rio de Janeiro, Brazil, were analyzed using the validated method and none of them presented residues of the searched macrolides and quinolones, with a screening target value of 5 µg kg^-1.

Transformation mechanisms of tetracycline by horseradish peroxidase with/without redox mediator ABTS for variable water chemistry

The threat of antibiotics in the environment causing antibiotics resistance is a global health concern. Enzymes catalyze pollutant transformations, and how commercially available enzymes like horseradish peroxidase (HRP), with or without a redox mediator, may be used to degrade antibiotics in water treatment is of great interest. This work demonstrates tetracycline transformation by HRP, and how it is significantly enhanced by free radicals created from the mediator 2,2-Azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Water temperature and pH strongly influence the tetracycline removal rate due to their correlation with the enzyme activity, abundance and stability of ABTS^•+. Four transformation products were identified in the pure HRP system using a liquid chromatography tandem mass spectrometry hybrid quadrupole-orbitrap mass spectrometer system. Addition of 25 μmol L^-1 ABTS not only accelerated the degradation of tetracycline, but also expanded the range of degradation pathways. Potential tetracycline transformation pathways are proposed based on these observations, which include a range of mechanisms such as hydroxylation, demethylation, dehydration, decarbonylation and secondary alcohol oxidation. Despite of decreased efficiency, the HRP/ABTS system was able to degrade tetracycline in a domestic wastewater treatment plant effluent matrix, which demonstrates the potential of the system to be utilized in wastewater treatment.

Hydrophilic interaction liquid chromatography coupled to quadrupole time-of-flight mass spectrometry as a potential combination for the determination of sulfonamide residues in complex infant formula matrices

An accurate, sensitive and selective analytical method is proposed for sulfonamide residues analysis in infant formulas based on hydrophilic interaction liquid chromatography (HILIC) and quadrupole time-of-flight mass spectrometry in full scan mode. The sample preparation approach involves low-temperature lipid precipitation followed by dispersive solid-phase extraction with PSA and C₁₈ sorbents, which was successfully optimized using Plackett-Burman design. In order to achieve high analytical sensitivity, the influence of HILIC conditions on sulfonamide ionization was investigated, such as the mobile phase composition, buffer concentration, and sample diluent for injection. The method performance characteristics, including linearity (range 5-120 µg kg^-1), reliable limits of quantification (between 5 and 20 µg kg^-1), recovery (72.9-109.2%) and precision (coefficient of variation values ≤ 19.8%) under repeatability and within-laboratory reproducibility conditions, were in accordance with the Codex Alimentarius Commission CAC/GL 71-2009 for quantitative analytical methods for veterinary drug residues in foods. Moreover, adequate identification of the compounds was provided with accurate mass measurement of both precursor and fragment ions in one single run. Finally, the developed method was applied to thirty-five powdered milk-based infant formula samples available in the Brazilian market.

Comparison of flavonoids and phenylpropanoids compounds in Chinese water chestnut processed with different methods

Different processing methods of Chinese water chestnut (CWC; Eleocharis dulcis (Burm.f.) Trin. ex Hensch.) steaming with skin (WPC), cooking with skin (WPS), steaming with peeling (PS), fresh cutting (FF) and cooking with peeling (PC) were compared. Liquid chromatography-mass spectrometry was used to analyze the metabolic profiles of the processed samples. A total of 454 metabolites, including 123 flavonoids and 57 phenylpropanoids, were characterized. The flavonoid and phenylpropanoid profiles were distinguished using PCA. Eighteen flavonoids and six phenylpropanoids were detected and quantitated in the WPC and WPS samples but not in the FF, PC and PS samples. In addition to the O-hexoside of tricin, kaempferol and luteolin were the predominant flavonoids in the WPC and WPS samples, and all three compounds were higher in the WPC and WPS samples than in the FF sample. This study provides new results regarding differences in the metabolite profile of CWC processed with different methods.

Gold nanostars-enhanced Raman fingerprint strip for rapid detection of trace tetracycline in water samples

Rapid and accurate detection of antibiotics at trace levels in food represents a great challenge. Tetracycline (TC), as a sort of broad-spectrum antibiotic, has been extensively used in animal infection therapy and animal husbandry as growth promoters. Large amounts of TC residues in animal-derived foods affect food quality and safety, and cause undesirable side effects such as allergic reactions and bacterial antibiotic resistance. Here, a Raman fingerprint strip sensor was reported based on surface-enhanced Raman scattering technology and demonstrated for ultrasensitive detection of TC. In this approach, 4-aminothiophenol (4-ATP) modified gold nanostars (GNSs) were used as a strong Raman reporter, which was coated with anti-TC monoclonal antibody serving as a biorecognition to acquire both visual and Raman signals on the test line. To demonstrate the performance of this strip, TC standard solutions with concentrations ranging from 0.5 to 50 ng/mL was detected, the limit of the detection (LOD) for the Raman signal was 0.04 ng/mL, which was 100 times more sensitive than those of color intensity quantifications. The other analogues, oxytetracycline, and chlortetracycline were detected using this method, making them suitable for the samples with TC analogues screening.

Indirect Competitive Determination of Tetracycline Residue in Honey Using an Ultrasensitive Gold-Nanoparticle-Linked Aptamer Assay

Tetracycline residue in honey has become an increasingly important food safety problem. In this work, an ultrasensitive gold nanoparticles (AuNPs)-linked aptamer assay was developed to determine the tetracycline residue in honey. First, a tetracycline–bovine serum albumin conjugate coating was applied to a microplate. Then, with the incubation of AuNPs-linked aptamer, the fixed tetracycline in the microplate competed for the limited aptamer with the free tetracycline in the sample. Higher amounts of free tetracycline in the sample were associated with more competitive binding of aptamer-AuNPs, and the aptamer-AuNPs binding with tetracycline-BSA was lower. Finally, as a kind of nanozyme, AuNPs exhibited peroxidase activity and oxidized 3,3′,5,5′-tetramethylbenzidine, transforming it from colorless to blue, and achieving the measurement at 652 nm. The analytical performance—including linearity, limit of detection, selectivity, precision, repeatability, and accuracy—has been investigated. It was successfully applied to the determination of tetracycline in honey samples with high accuracy and sensitivity.

Interactions of tetracyclines with milk allergenic protein (casein): a molecular and biological approach

Tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC) interactions with the allergenic milk protein casein (CAS) were here evaluated simulating food conditions. The antibiotics assessed interact with CAS through static quenching and form non-fluorescent complexes. At 30 °C, the binding constant (K_b) varied from 0.05 to 1.23 × 10⁶ M^-1. Tetracycline interacts with CAS preferably through electrostatic forces, while oxytetracycline and chlortetracycline interactions occur by hydrogen bonds and van der Waals forces. The interaction process is spontaneous, and the magnitude of interaction based on K_b values, followed the order: TC < CTC < OTC. The distances between the donor (protein) and the receptors (TC, OTC, and CTC) were determined by Förster resonance energy transfer (FRET) and varied from 3.67 to 4.08 nm. Under natural feeding conditions, the citrate decreased the affinity between TC and CAS; a similar effect was observed for OTC in the presence of Ca(II), Fe(III) and lactose. Synchronized and three-dimensional (3D) fluorescence studies indicated alterations in the original protein conformation due to the interaction process, which may influence allergenic processes. In addition, complexation with CAS modulated the antimicrobial activity of CTC against S. aureus, demonstrated that the interaction process possibly alters the biological properties of antibiotics and the own protein, in the food conditions.Communicated by Ramaswamy H. Sarma.

Presence of emerging contaminants in baby food

Food safety becomes imperative when it aims to protect infants. The objective of this study was to investigate the presence of emerging contaminants of which some act as endocrine-disruptors in baby food. Persistent organic pollutants (POPs), perfluoroalkyl substances (PFASs), parabens and antibiotics were analysed in 112 baby food of different categories (meat, fish, vegetables, fruit, cheese). As regard POPs, PFASs and antibiotics, no residues were detected, while one sample showed methyl-paraben (4.14 ng g^-1), whereas another three contained propyl-paraben (median 1.70 ng g^-1). Special attention must be paid on parabens metabolites, as 4-hydroxybenzoic acid, the principal parabens metabolite, was detected in all samples (median 176.7 ng g^-1). It may be present as a degradation product, but also, it can be released from vegetables and fruits during food processing. It is recommended to collect more data on natural vs non-natural occurrence of parabens and metabolites to evaluate the exposure of sensitive population vs ADI published by the European Food Safety Authority and European Medicines Agency.

A highly fluorescent lanthanide metal-organic framework as dual-mode visual sensor for berberine hydrochloride and tetracycline

A microscale highly fluorescent Eu metal-organic framework (Eu-MOF) was synthesized with terephthalic acid and 1H-1,2,4-triazole-3,5-diamine by one-pot hydrothermal method. And it was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, powder X-ray diffraction, fluorescence spectroscopy, thermogravimetric analysis, and energy dispersive X-ray mapping. The prepared Eu-MOF has high quantum yield of 30.99%, excellent water dispersibility, good fluorescence stability, and favorable thermal stability. Based on the distinctly different fluorescence responses of different emission, the prepared Eu-MOF was used as dual-mode visual sensor for the sensitive detection of berberine hydrochloride and tetracycline. The limits of detection are 78 nM and 17 nM, respectively. The sensing mechanism was also discussed. Moreover, a filter paper sensor has been designed for sensing tetracycline with a notable fluorescence color change from blue to red. The prepared Eu-MOF is promising to be developed as a multi-mode luminescent sensor for visual detection in biochemical analysis. Graphical abstract Illustration of the synthesis of Eu-MOF and its sensing applications for berberine hydrochloride and tetracycline.

Determination of Florfenicol, Thiamfenicol and Chloramfenicol at Trace Levels in Animal Feed by HPLC⁻MS/MS

Administration of florfenicol and thiamfenicol through medicated feed is permitted within the European Union, always following veterinary prescription and respecting the withdrawal periods. However, the presence of low levels of florfenicol, thiamfenicol, and chloramfenicol in non-target feed is prohibited. Since cross-contamination can occur during the production of medicated feed and according to Annex II of the European Regulation 2019/4/EC, the control of residue levels of florfenicol and thiamfenicol in non-target feed should be monitored and avoided. Based on all the above, a sensitive and reliable method using liquid chromatography tandem mass spectrometry was developed for the simultaneous detection of chloramfenicol, florfenicol, and thiamfenicol at trace levels in animal feed. Analytes were extracted from minced feed with ethyl acetate. Then, the ethyl acetate was evaporated, the residue was resuspended in Milli-Q water and the extract filtered. The method was in-house validated at carryover levels, with concentration ranging from 100 to 1000 µg/kg. The validation was conducted following the European Commission Decision 2002/657/EC and all performance characteristics were successfully satisfied. The capability of the method to detect amfenicols at lower levels than any prior perspective regulation literature guarantees its applicability in official control activities. The developed method has been applied to non-compliant feed samples with satisfactory results.

Current trends on microextraction by packed sorbent – fundamentals, application fields, innovative improvements and future applications

MEPS, the acronym of microextraction by packed sorbent, is a simple, fast and user- and environmentally-friendly miniaturization of the popular solid-phase extraction technique (SPE).

Biomass-derived nitrogen-doped carbon quantum dots: highly selective fluorescent probe for detecting Fe3+ ions and tetracyclines

Nitrogen-doped carbon quantum dots (N-CQDs) were successfully synthesized using rice residue and glycine as carbon and nitrogen sources by one-step hydrothermal method. High quantum yield (23.48%) originated from the effective combination of nitrogen with various functional groups (CO, NH, CN, COOH and COC). The N-CQDs showed a fluorescence with the wavelength varied from 420 to 500 nm and the maximum emission wavelength being at 440 nm. N-CQDs have been importantly applied as probe to detect Fe³⁺ and tetracycline (TCs) antibiotics with remarkable performance. Using the linear relationship between fluorescence intensity and Fe³⁺ concentration, the N-CQDs could be employed as a simple, efficient sensor for ultrasensitive Fe³⁺ detection ranging from 3.32 to 32.26 µM, with a limit of detection (LOD) of 0.7462 µM. The N-CQDs showed the applicability to detect TCs. The detection limits of tetracycline, terramycin and chlortetracycline were 0.2367, 0.3739 and 0.2791 µM, respectively. The results of TC by fluorescence method in real water samples were in good agreement with standard Ultraviolet-visible (UV-vis) method. The N-CQDs have various potential applications including sensitive and selective detection of Fe³⁺ and TCs, and cellular imaging with low cytotoxicity, good biocompatibility and high permeability.

Oxytetracycline effects in specific biochemical pathways of detoxification, neurotransmission and energy production in Oncorhynchus mykiss

Oxytetracycline (OTC) is a tetracycline antibiotic, widely used in human and veterinary medicines, including in aquaculture. Given this use, OTC has been detected in different aquatic environments. Some recent works have demonstrated unintentional biological activity of OTC in non-target aquatic organisms. This study investigated the acute and chronic effects of OTC on the physiology of the fish species Oncorhynchus mykiss (rainbow trout), namely through the quantification of the activity of enzymes involved in different biochemical pathways, such as detoxification (phase II - glutathione S-transferases - GSTs, uridine-diphosphate-glucuronosyltransferases - UGTs), neurotransmission (acetylcholinesterase - AChE) and energy production (lactate dehydrogenase - LDH). The here-obtained data demonstrated the induction of GSTs activity in gills, and inhibition of AChE activity in eyes tissue, in chronically exposed organisms, as well as alterations in LDH activity following both exposures. Considering this set of results, we can infer that OTC exposure may have induced the glutathione pathway of detoxification in gills with the involvement of GSTs, or indirectly due to the metabolites that may have been produced. In turn, these metabolites may have interfered with the mechanism of neurotransmission, also causing physiological and biochemical disturbances in rainbow trout after OTC exposure, namely disturbances in energetic metabolism. In addition, it is important to stress that such occurrences took place at low, environmentally realistic levels of OTC, suggesting that organisms exposed in the wild may be putative targets of toxic effects by commonly used drugs such as antibiotics.

Visual and fluorometric lateral flow immunoassay combined with a dual-functional test mode for rapid determination of tetracycline antibiotics

A fluorometric immunochromatographic assay (FICA) is described where ZnCdSe/ZnS quantum dots (QDs) act as fluorescent label and gold nanoparticles (AuNPs) act as quencher. The assay works in the "turn-on" mode, i.e. the fluorescent signal (best measured at excitation/emission wavelengths of 302/525 nm) increases with the increase of analyte concentration. This assay can detect tetracycline antibiotics including tetracycline, oxytetracycline, chlortetracycline, and doxycycline. It is not interfered by other veterinary drugs. The visual limits of detection (LODs) for the tetracycline antibiotics are 2 μg·L^-1 in buffer, 20 μg·L^-1 in milk, and 40 μg·kg^-1 in animal muscle tissue. The assay (including sample treatment) can be performed within 30 min. The FICA based on "turn on" mode is more sensitive than the colloidal gold-based immunochromatographic assay (CGICA) and quantum dot-based immunochromatographic assay (QDICA) based on "turn off" mode using either AuNPs or QDs as signal labels. One strip can simultaneously provide the fluorescent test results in the "turn on" mode on the basis of QD luminescence quenching under UV light. The colorimetric test is of the "turn off" mode based on the formation of a red coloration due to the use of AuNPs under natural light. The use of such a dual-functional test mode allows for rapid semi-quantitative determination of tetracycline antibiotics in milk and tissue samples. Graphical abstract Schematoc of a fluorometric immunochromatographic assay (FICA) based on fluorescence quenching of quantum dot (QD) by gold nanoparticle (AuNP) combined with a dual-functional test mode under UV light (turn on mode) and natural light (turn off mode) to visually detect tetracycline antibiotics.

Rapid identification of Streptomyces tetracycline producers by MALDI-TOF mass spectrometry

The main objective of this study was using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for assembling of DSM (German Collection of Microorganisms) Streptomyces spectral database and identification of wild Streptomyces cultures, which were clustered by MALDI-TOF Biotyper OC software as well as for teracycline detection by observing of obtained spectra using flexAnalysis software. Production of tetracycline was confirmed by thin-layer chromatography. Presence of tetracycline mass spectrum was verified by several tetracycline producers (Streptomyces aureofaciens LMG 5968, S. aureofaciens 84/25, and S. aureofaciens BMK) and by pure tetracycline mass. Our results showed that it is possible to use MALDI-TOF MS for identification of tetracycline producers within Streptomyces genera by several easy steps. The purpose of this study was to establish cheap and quick detection of tetracycline producers.

An automated optofluidic biosensor platform combining interferometric sensors and injection moulded microfluidics

A primary limitation preventing practical implementation of photonic biosensors within point-of-care platforms is their integration with fluidic automation subsystems. For most diagnostic applications, photonic biosensors require complex fluid handling protocols; this is especially prominent in the case of competitive immunoassays, commonly used for detection of low-concentration, low-molecular weight biomarkers. For this reason, complex automated microfluidic systems are needed to realise the full point-of-care potential of photonic biosensors. To fulfil this requirement, we propose an on-chip valve-based microfluidic automation module, capable of automating such complex fluid handling. This module is realised through application of a PDMS injection moulding fabrication technique, recently described in our previous work, which enables practical fabrication of normally closed pneumatically actuated elastomeric valves. In this work, these valves are configured to achieve multiplexed reagent addressing for an on-chip diaphragm pump, providing the sample and reagent processing capabilities required for automation of cyclic competitive immunoassays. Application of this technique simplifies fabrication and introduces the potential for mass production, bringing point-of-care integration of complex automated microfluidics into the realm of practicality. This module is integrated with a highly sensitive, label-free bimodal waveguide photonic biosensor, and is demonstrated in the context of a proof-of-concept biosensing assay, detecting the low-molecular weight antibiotic tetracycline.

Histological alterations in gills and liver of rainbow trout (Oncorhynchus mykiss) after exposure to the antibiotic oxytetracycline

The aim of this study was to investigate the histopathological effects of oxytetracycline (OTC) on the gill and liver tissues of rainbow trouts (Oncorhynchus mykiss) following acute (96h: 0.005-50mg/L) and chronic (28days: 0.3125-5μg/L) exposures. Results suggest the existence of a cause-and-effect relationship between the exposure to OTC and tissue damage. Most predominant disorders observed in gills were progressive (e.g. hypertrophy of mucous cells and hyperplasia of epithelial cells) in acute exposure and regressive (e.g. lamellar fusion, epithelial lifting of lamellae and some changes in tissue architecture) in chronic exposure. However, only the acute exposure was responsible for a significant increase of the total gill pathological index. PAGE index, reflecting the extent of gill tissue available for gas exchanges in fish, remained unchanged for both exposures. In liver, circulatory (e.g. hemorrhage and increase of sinusoidal space), regressive (e.g. pyknotic nucleus, vacuolization and hepatocellular degenerations) and progressive (e.g. hypertrophy of hepatocytes) changes were observed, but just after acute exposure. After chronic exposure, only inflammatory changes (e.g. leucocytes infiltration) were observed. Following both exposures, a significant increase of the total liver pathological index was recorded. Despite the increase of the histological damage in individuals exposed to OTC, lesions observed were of minimal or moderate pathological importance, non-specific and reversible. The data gathered following acute and chronic exposures also suggest the onset of adaptive mechanisms of fish, namely for longer exposure periods. Furthermore the observed histological alterations appear to be result of several physio-metabolic disorders consequence of the biochemical and molecular modes of action of OTC.