Matrix Solid-Phase Dispersion Extraction and Capillary Electrophoresis Determination of Tetracycline Residues in Milk

Preparation of protein-resistant magnetic molecularly imprinted polymers as solid-phase extraction adsorbents via a one-stone-two-birds strategy for selective enrichment of tetracycline in milk

The widespread presence of antibiotic residues in animal-derived foods poses serious risks to public health and the environment, emphasizing the need for urgent action. This study presented a novel lightweight, popcorn-like magnetic molecularly imprinted polymer (LPR-MMIPs) with protein-resistant properties, for the selective enrichment of tetracycline (TC) antibiotics in milk. During the preparation of LPR-MMIPs, bovine serum albumin (BSA) was used as the functional monomer, and tris(2-carboxyethyl)phosphine (TCEP) served as the reducing agent. Using a "one-stone-two-birds" strategy, TCEP not only converted the α-helical structure of BSA to a β-folded conformation for imprinting on the Fe3O4 carrier, but also etched the Fe3O4 into a lightweight, popcorn-like structure under acidic conditions. The BSA imprinting layer excludes proteins through electrostatic repulsion, and the reduced amount of carrier material significantly enhances the adsorption efficiency (Q = 12.7 mg g-1), selectivity (IF = 3.02, SC > 1.53), and reusability. Meanwhile, LPR-MMIPs, as solid-phase extraction adsorbents, have been successfully applied to the specific adsorption and separation of TC in real milk samples. The established method exhibits good accuracy, precision, and sensitivity, as evidenced by the low LOD (1.80 ng mL-1) and LOQ (5.60 ng mL-1), low RSDs (≤5.4 %), and high recovery rates (≥94.5 %). Besides, the method demonstrates excellent practical applicability for milk, offering a novel strategy for the selective enrichment of trace antibiotics in milk.

Highly selective and efficient AIEE active fluorescence probe for the detection of doxycycline in biological and environmental samples with extensive DFT support

A highly selective naphthalimide based fluorescent probe PBQ was designed for investigation of doxycycline (DOX) in various real samples. The synthesized probe PBQ showed maximum emission intensity at 395 nm and exhibited selective quenching response-based on photoinduced electron transfer (PET) mechanism even in the presence of various competing and interfering drugs, amino acids, cations and anions. Furthermore, probe PBQ showed excellent AIEE properties with red shift in maximum emission wavelength due to formations of J-aggregates. The enlargement in size of probe PBQ with the formation of aggregates was verified through DLS analysis. The LOD of probe PBQ was found 66 nM for DOX. The nature of interaction and sensitivity of probe PBQ for DOX has been assessed through UV-visible, fluorescence, SEM, 1H NMR, LC-MS and FTIR titration experiments. The non-covalent nature of interaction, π-π stacking, transfer of charge density, and reduction of HOMO LUMO energy gap between probe PBQ and PBQ-DOX complex has also been revealed by DFT calculations. Furthermore, probe PBQ was extensively utilized for detection of DOX in blood, urine and other industrial wastewater samples.

Nanozyme-based colorimetric and smartphone imaging advanced sensing platforms for tetracycline detection and removal in food

The presence of antibiotic residues poses a significant threat to food assurance, triggering widespread concerns. Therefore, the prompt and accurate detection and removal of antibiotic residues are essential for ensuring food safety. In this study, an aptmer modified triple-metal nanozyme (apt-TMNzyme) sensor was developed, which achieved a portable, visual, intelligent, and fast determination for tetracycline (TET). The proposed apt-TMNzyme exhibited willow leaf-like morphology, high specific surface area and excellent TET adsorption and removal properties. The experiments showed that the apt-TMNzyme had outstanding peroxidase activity and could catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue product in the presence of H2O2, which provided a visual response signal to TET. This sensor was capable of quantifying TET within a concentration range of 0.2 nM-70 μM, achieving a detection limit of 7.1 nM under optimal conditions. When tested on real food samples, our sensor produced results that closely paralleled those achieved through high-performance liquid chromatography. To improve accessibility and user-friendliness, we also designed a colorimetric testing paper integrated with a smartphone application for intuitive and intelligent detection of TET, which enables the quantitative determination of TET in the concentration range of 0.003-60 μM, the detection limit was 5.1 μM. This integrated portable sensor not only streamlines the testing process, saving time and costs, but also offers a promising solution for rapid and sensitive detection of antibiotic residues.

Detection of Tetracycline in Farm Wastewater by Nitrogen-doped Carbon Quantum Dots

The detection of tetracycline antibiotics in environmental waters is crucial due to their widespread use, persistence, and potential toxicity. Herein, a method for the specific detection of tetracycline in aquaculture wastewater using a nitrogen-doped carbon quantum dots fluorescence probe is reported. Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized in one step via a hydrothermal method, employing citric acid as the carbon source and diethylenetriamine as the nitrogen source. The resulting N-CQDs exhibit excellent stability, solubility and fluorescence properties. Upon the introduction of tetracycline, a fluorescence burst can be observed, indicating that the N-CQDs function as a ratio fluorescence probe. The fluorescence burst phenomenon is primarily due to the internal filtering effect. In the case of N-CQDs, this burst is attributed to the overlap between the absorption spectrum of tetracycline and the emission spectrum of the carbon quantum dots, which results in internal filtering. The linear range for tetracycline detection spans from 54.2 nM to 0.8 μM, with a detection limit of 54.2 nM. The developed fluorescence probe shows potential for application in detecting tetracycline in real water samples.

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

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

Pseudo-Siamese network combined with label-free Raman spectroscopy for the quantification of mixed trace amounts of antibiotics in human milk: A feasibility study

The utilization of antibiotics is prevalent among lactating mothers. Hence, the rapid determination of trace amounts of antibiotics in human milk is crucial for ensuring the healthy development of infants. In this study, we constructed a human milk system containing residual doxycycline (DXC) and/or tetracycline (TC). Machine learning models and clustering algorithms were applied to classify and predict deficient concentrations of single and mixed antibiotics via label-free SERS spectra. The experimental results demonstrate that the CNN model has a recognition accuracy of 98.85% across optimal hyperparameter combinations. Furthermore, we employed Independent Component Analysis (ICA) and the pseudo-Siamese Convolutional Neural Network (pSCNN) to quantify the ratios of individual antibiotics in mixed human milk samples. Integrating the SERS technique with machine learning algorithms shows significant potential for rapid discrimination and precise quantification of single and mixed antibiotics at deficient concentrations in human milk.

A combined experimental and theoretical approach for doxycycline sensing using simple fluorescent probe with distinct fluorescence change in wide range of interferences

Overuse of doxycycline (DOXY) can cause serious problems to human health, environment and food quality. So, it is essential to develop a new sensing methodology that is both sensitive and selective for the quantitative detection of DOXY. In our current research, we synthesized a simple fluorescent probe 4,4'-bis(benzyloxy)-1,1'-biphenyl (BBP) for the highly selective detection of doxycycline by through fluorescence spectroscopy. The probe BBP displayed ultra-sensitivity towards doxycycline due to Forster resonance energy transfer (FRET). Fluorescence spectroscopy, density functional theory (DFT), 1H NMR titration, UV-Vis, and Job's plot were used to confirm the sensing mechanism. The charge transfer between the probe and analyte was further examined qualitatively by electron density differences (EDD) and quantitively by natural bond orbital (NBO) analyses. Whereas the non-covalent nature of probe BBP towards DOXY was verified by theoretical non-covalent interaction (NCI) analysis as along with Bader's quantum theory of atoms in molecules (QTAIM) analysis. Furthermore, probe BBP was also practically employed for the detection of doxycycline in fish samples, pharmaceutical wastewater and blood samples.

An aptamerelectrochemical sensor based on functional carbon nanofibers for tetracycline determination

Fe-Co@CNF was synthesized by electrospinning technology, and AuNPs was loaded onto Fe-Co@CNF by in-situ reduction to obtain Fe-Co@CNF@AuNPs composite material, which was used as the working electrode based on Au-S bond cooperation. The tetracycline electrochemical sensing interface Fe-Co@CNF@AuNPs@Apt was constructed by connecting mercaptoylated tetracycline (TC) aptamers on Fe-Co@CNF@AuNPs surface. The morphology and composition of Fe-Co@CNF@AuNPs composites were characterized by SEM, TEM, EDS, XRD and XPS, and the electrochemical properties of tetracycline were evaluated by CV and DPV. The results showed that the addition of Fe and Co did not destroy the structure of the original carbon nanofibers, and their synergistic effect enhanced the electrocatalytic performance, effective electrode area and electron transfer ability of carbon nanofibers. AuNPs are evenly distributed over the fibers, which effectively improves the electrical conductivity of the material. Under the optimal conditions, the theoretical detection limit of tetracycline was 0.213 nM, and the linear detection range was 5.12-10 mM, which could successfully detect tetracycline in milk.

Metal-organic-framework-confined quantum dots enhance photocurrent signals: A molecularly imprinted photoelectrochemical cathodic sensor for rapid and sensitive tetracycline detection

BACKGROUND

Tetracycline (TC), a cost-effective broad-spectrum antibacterial drug, has been excessively utilized in the livestock and poultry industry, leading to a serious overabundance of TC in livestock wastewater. However, conventional analytical methods such as liquid chromatography and gas chromatography face challenges in achieving sensitive detection of trace amounts of TC in complex substrates. Therefore, it is imperative to develop a highly sensitive and anti-interference analytical method for the detection of tetracycline in livestock wastewater.

RESULTS

A porphyrin-based MOF (PCN-224)-confined carbon dots (CDs) material (CDs@PCN-224) was synthesized by a "bottle-around-ship" strategy. The reduced carrier migration distance is conducive to the separation of electron-hole pairs and enhanced the photocurrent signal due to the tight coupling of CDs and PCN-224. Further, molecularly imprinted polymer (MIP) was synthesized by rapid in-situ UV-polymerization and employed as a recognition element. The specific recognition of the target by imprinted cavities blocks electron transfer, resulting in a "turn off" response signal, thus realizing the selective detection of TC. Under optimal conditions, the constructed MIP-PEC cathodic sensor detected 1.00 × 10-12 M to 1.00 × 10-7 M of TC sensitively, with a limit of detection of 3.72 × 10-13 M. In addition, the proposed MIP-PEC sensor demonstrated good TC detection performance in actual livestock wastewater.

SIGNIFICANCE

The strategy based on MOF pore-confined quantum dots can effectively enhance the photocurrent response of the photosensitive substrate. Simultaneously, the MIP constructed by in-situ rapid UV-polymerization showed excellent anti-interference and reusable properties. This work provides a promising MIP-PEC cathodic sensing method for the rapid and sensitive detection of antibiotics in complex-matrix environmental samples.

Upcycling Waste: Citrus limon Peel-Derived Carbon Quantum Dots for Sensitive Detection of Tetracycline in the Nanomolar Range

In this work, a sustainable method was developed for the production of water-soluble carbon quantum dots employing a green approach. The synthetic protocol was employed using the microwave pyrolysis technique, while lemon peel served as a carbon precursor. Fabrication of highly fluorescent lemon-peel-derived CQDs (LP-CQDs) having inherent nitrogen functionality was validated by X-ray photoelectron spectroscopy, FTIR, X-ray diffraction, Raman spectroscopic analysis, and TEM techniques. The average particle size of fabricated LP-CQDs was 4.46 nm. LP-CQDs yielded a remarkable quantum yield of 49.5%, which displayed excellent salinity, photostability, storage time, conditions, and pH stability. LP-CQDs displayed encouraging results for tetracycline (TC) detection using a PL turn-off approach. The sensitivity of LP-CQDs toward TC was seen in a nanomolar range having a detection limit of 50.4 nM. Method validation was comprehensively studied to ensure the precision of the nanosensor. A complete analysis of different photophysical parameters of LP-CQDs was performed with TC to gain a deeper understanding of the sensing mechanism. Fabricated LP-CQDs showed fluorescence quenching toward TC, elucidated by the inner filter effect (IFE) mechanism. The synthesized nanoprobe demonstrated a lesser detection limit with a broad linear range, enabling facile, cheap, environmentally friendly, and fast detection of TC. Practicality of the detection method was assessed through analysis of real samples, resulting in satisfactory recovery percentage and relative standard deviation with respect to the developed probes. Furthermore, LP-CQDs were used as fluorescent inks and to fabricate paper-based fluorescent strips. This study lays the door for the sensing platform of LP-CQDs toward detection of TC, which may impact the potential role of environmental sustainability.

A Turn-Off Fluorescent Biomimetic Sensor Based on a Molecularly Imprinted Polymer-Coated Amino-Functionalized Zirconium (IV) Metal-Organic Framework for the Ultrasensitive and Selective Detection of Trace Oxytetracycline in Milk

Developing sensitive and effective methods to monitor oxytetracycline residues in food is of great significance for maintaining public health. Herein, a fluorescent sensor (NH₂-UIO-66 (Zr)@MIP) based on a molecularly imprinted polymer-coated amino-functionalized zirconium (IV) metal-organic framework was successfully constructed and first used for the ultrasensitive determination of oxytetracycline. NH₂-UIO-66 (Zr), with a maximum emission wavelength of 455 nm under 350 nm excitation, was prepared using a microwave-assisted heating method. The NH₂-UIO-66 (Zr)@MIP sensor with specific recognition sites for oxytetracycline was then acquired by modifying a molecularly imprinted polymer on the surface of NH₂-UIO-66 (Zr). The introduction of NH₂-UIO-66 (Zr) as both a signal tag and supporter can strengthen the sensitivity of the fluorescence sensor. Thanks to the combination of the unique characteristics of the molecularly imprinted polymer and NH₂-UIO-66 (Zr), the prepared sensor not only exhibited a sensitive fluorescence response, specific identification capabilities and a high selectivity for oxytetracycline, but also showed good fluorescence stability, satisfactory precision and reproducibility. The fabricated sensor displayed a fluorescent linear quenching in the OTC concentration range of 0.05-40 μg mL^-1, with a detection limit of 0.012 μg mL^-1. More importantly, the fluorescence sensor was finally applied for the detection of oxytetracycline in milk, and the results were comparable to those obtained using the HPLC approach. Hence, the NH₂-UIO-66 (Zr)@MIP sensor possesses great application potential for the accurate evaluation of trace oxytetracycline in dairy products.

UiO-66-NH2 based fluorescent sensing for detection of tetracyclines in milk

In this work, a fluorescent sensor based on a zirconium-based metal organic framework was prepared for the detection of tetracyclines (TCs) in milk. The UiO-66-NH2 fluorescent sensor was synthesized by a simple microwave-assisted method with 2-aminoterephthalic acid and zirconium chloride as precursors. In the presence of target TCs, the synergistic effect of the inner filter effect (IFE) and photo-induced electron transfer (PET) was responsible for the fluorescence quenching of UiO-66-NH2, and the fluorescence sensor showed a rapid fluorescence quenching response (5 min) to target TCs. The proposed UiO-66-NH2 sensor had good sensitivity and selectivity, and under the optimal conditions possessed detection limits of 0.449, 0.431, and 0.163 μM for tetracycline (TET), oxytetracycline (OTC), and doxycycline (DOX), respectively. Besides, the UiO-66-NH2 sensor was successfully applied to the quantitative detection of TCs in milk samples with reasonable recoveries of 93.26-115.17%, and the detection results achieved from the as-fabricated fluorescence sensing assay were consistent with those of high-performance liquid chromatography (HPLC), indicating the potential applicability of the UiO-66-NH2 sensor for detecting TCs in actual food samples.

A REVIEW ON DETERMINATION OF THE VETERINARY DRUG RESIDUES IN FOOD PRODUCTS

In this paper, we discuss veterinary medicine and its applications in the food field as well as its risk to the health of humans and animals by the residues. We review how the veterinary residues enter and cause some detrimental effects. We also mention two techniques to determine the residue of veterinary medication that existed in food originating from animals, including classic and advanced techniques. Finally, we discuss the potential of various developed methods compared to some traditional techniques.

Smartphone-assisted ratiometric fluorescence sensing platform for the detection of doxycycline based on BCNO QDs and calcium ion

A novel colorimetric and ratiometric fluorescence sensor has been established based on boron carbon oxynitride quantum dots (BCNO QDs) and Ca²⁺ for the detection of doxycycline (DOX). BCNO QDs were synthesized by microwave-assisted method with boric acid and ethylenediamine. The fluorescence of BCNO QDs at 425 nm was quenched due to the electrostatic interaction and inner filter effect with doxycycline. Meanwhile, doxycycline was combined with Ca²⁺ to form a fluorescence complex, which generated a new fluorescence peak at 520 nm. The fluorescence intensity ratio (F₅₂₀/F₄₂₅) has a good linear relationship with doxycycline concentration, and the detection limit is 25 nM. Moreover, the fluorescence of the reaction solution showed a concentration-dependent visual color change from blue to green. In order to facilitate further application, a portable fluorescent test paper which is easy to store was prepared. The RGB values of the reaction solution and corresponding test paper were identified by smartphone, and the visual detection of doxycycline was performed by digital image colorimetric analysis. The application of smartphone and fluorescent test paper can effectively shorten the detection time and simplified the operation, providing an effective scheme for quantitative detection of doxycycline in actual samples. Overall, this work provides a method for the detection of doxycycline and shows that the BCNO QDs have great potential application in food safety.

Photoelectrochemical aptasensor for sensitive detection of tetracycline in soil based on CdTe-BiOBr heterojunction: Improved photoactivity enabled by Z-scheme electron transfer pathway

Exploring effective methods for tetracycline (TC) detection in soil has great significance because of its emerging environmental problem and increasing threat to soil quality and general public health worldwide. In this work, a sensitive photoelectrochemical (PEC) aptasensor toward TC detection was designed and constructed based on an efficient photosensitive material of Z-scheme CdTe-BiOBr heterojunction. Due to the sensitization of CdTe quantum dots (QDs) on the BiOBr nanoflowers, the photocurrent intensity of the CdTe-BiOBr heterojunction was enhanced about 5.0-fold and 8.0-fold than that of pure BiOBr and CdTe under visible-light irradiation, which was attributed to the low electron-hole combination efficiency, high visible light utilization efficiency, and high carrier density of the heterojunction. On the merits of the excellent PEC activity of the CdTe-BiOBr and the specificity of the aptamer, the proposed PEC aptasensor has the advantages of satisfying linear range (from 10 to 1500 pM), low detection limit (9.25 pM), good selectivity, and reproducibility. In addition, acceptable accuracy was obtained for TC detection in real soil sample, giving acceptable accuracy in comparison with the referenced high-performance liquid chromatography-diode array detector method, revealing a promising avenue for accurate and ultrasensitive estimation of other kinds of contaminants in the broad field of analysis.

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.

A ratiometric fluorescent probe based on sulfur quantum dots and calcium ion for sensitive and visual detection of doxycycline in food

The residue of doxycycline in food can cause harm to human. Therefore, the detection of doxycycline residue is necessary. Herein, a ratiometric fluorescent probe was designed based on sulfur quantum dots (S dots) and Ca²⁺. Due to static quenching and inter filter effect between doxycycline and S dots, doxycycline quenched fluorescence of S dots at 450 nm. Meanwhile, doxycycline and Ca²⁺ formed fluorescent complex through coordination to produce new peak at 520 nm. The ratio of fluorescence intensity (F₅₂₀/F₄₅₀) and doxycycline concentration showed good linear relationship with detection limit of 0.19 μM. The fluorescence color of S dots/Ca²⁺ changed from blue to light green with increasing doxycycline concentration, which was applied for visual semi-quantitative detection of doxycycline. Moreover, the method was used for detecting doxycycline in milk and fish samples with recoveries in the range of 91%-110%. The method showed good application potential in detection of doxycycline in food samples.

Voltage control for microchip capillary electrophoresis analyses

This paper presents an inexpensive and easy-to-implement voltage sequencer instrument for use in microchip capillary electrophoresis (MCE) actuation. The voltage sequencer instrument takes a 0-5 V input signal from a microcontroller and produces a reciprocally proportional voltage signal with the capability to achieve the voltages required for MCE actuation. The unit developed in this work features four independent voltage channels, measures 105 × 143 × 45 mm (width × length × height), and the cost to assemble is under 60 USD. The system is controlled by a peripheral interface controller and commands are given via universal serial bus connection to a personal computer running a command line graphical user interface. The performance of the voltage sequencer is demonstrated by its integration with a fluorescence spectroscopy MCE sensor using pinched sample injection and electrophoretic separation to detect ciprofloxacin in samples of milk. This application is chosen as it is particularly important for the dairy industry, where fines and health concerns are associated with the shipping of antibiotic-contaminated milk. The voltage sequencer instrument presented represents an effective low-cost instrumentation method for conducting MCE, thereby making these experiments accessible and affordable for use in industries such as the dairy industry.

Microchip capillary electrophoresis dairy device using fluorescence spectroscopy for detection of ciprofloxacin in milk samples

Detecting antibiotics in the milk supply chain is crucial to protect humans from allergic reactions, as well as preventing the build-up of antibiotic resistance. The dairy industry has controls in place at processing facilities, but controls on dairy farms are limited to manual devices. Errors in the use of these manual devices can result in severe financial harm to the farms. This illustrates an urgent need for automated methods of detecting antibiotics on a dairy farm, to prevent the shipment of milk containing antibiotics. This work introduces the microchip capillary electrophoresis dairy device, a low-cost system that utilizes microchip capillary electrophoresis as well as fluorescence spectroscopy for the detection of ciprofloxacin contained in milk. The microchip capillary electrophoresis dairy device is operated under antibiotic-absent conditions, with ciprofloxacin not present in a milk sample, and antibiotic-present conditions, with ciprofloxacin present in a milk sample. The response curve for the microchip capillary electrophoresis dairy device is found through experimental operation with varied concentrations of ciprofloxacin. The sensitivity and limit of detection are quantified for the microchip capillary electrophoresis dairy device.

New application of Mn-doped ZnS quantum dots: phosphorescent sensor for the rapid screening of chloramphenicol and tetracycline residues

In this work, a new application of Mn-doped ZnS quantum dots (Mn-ZnS QDs) was developed to screen chloramphenicol (CAP) and tetracycline (TC) residues simply and rapidly. Mn-ZnS QDs synthesized by a hydration method and modified by l-cysteine for better stability emit phosphorescence at 583 nm with the excitation wavelength at 289 nm. Based on the overlap of the Mn-ZnS QDs excitation spectra and CAP or TCs ultraviolet spectra, the excited light of the Mn-ZnS QDs was partially absorbed by CAP or TCs owing to the inner-filter effect (IFE), leading to a decrease in the phosphorescence intensity. The phosphorescence intensities of the samples prepared by mixing different TCs and CAP were in good agreement with the expected results from adding a single antibiotic sample. Therefore, the total molar concentrations of CAP and TCs could be screened based on the linear equation of a single standard substance. Represented by tetracycline (TC), as a member of the tetracycline family, under optimized conditions, showed a good linear relational concentration range over 4 orders of magnitude from 50 to 1.5 × 105 nM with a limit of detection (LOD; S/N ratio = 3) down to 8.6 nM. The phosphorescent sensor was also used to detect total TCs in actual samples successfully. The evaluations of the recovery rate and selectivity were good. These results demonstrated that the presented phosphorescent sensor can be a simple and rapid screening platform for CAP and TCs.

Synthesis and sensitive detection of doxycycline with sodium bis 2-ethylhexylsulfosuccinate based silver nanoparticle

The monitoring of residual antibiotics in the environment has gained a significant importance for the effective control, because of the high risk to human health. A simple strategy was designed for the green synthesis and detection of doxycycline (Dox) by using anionic surfactant sodium bis 2-ethylhexylsulfosuccinate based silver nanoparticles (AOT-AgNPs). The chemical reduction and capping of Ag⁺¹ ions was achieved by sulfonyl and carbonyl functional groups of AOT molecule. The AOT-AgNPs were found to have excellent stability at variable environmental parameters (i.e. temperature, storage period, salt concentration and pH) possibly due to the strong emulsifying nature of the surfactant. Mechanism of interaction between the AOT-AgNPs and Dox was established with UV/visible, Fourier transform infrared (FTIR) spectroscopy, Atomic force microscopy (AFM) and Dynamic light scattering (DLS) techniques, which suggests the interaction via aggregates formation. The synthesize probe could detect the Dox within 15 min over a wide range of concentrations from 0.1 to 140μM with limit of detection (LOD) of 0.2 μM. As proof of strategy, we have illustrated that the AOT-AgNPs also detect Dox in biological and environmental samples with negligible interference and very significant recovery rates. Moreover, non-toxic nature against various tested cell lines (i.e. normal mouse fibroblast (NIH-3 T3) and cancerous non-small lung carcinoma (NCI-H460)) and significant antimicrobial, antibiofilm and biofilm eradicating potential of AOT-AgNPs were provide ideal nanomaterial for further applications.

Advances in the Analysis of Veterinary Drug Residues in Food Matrices by Capillary Electrophoresis Techniques

In the last years, the European Commission has adopted restrictive directives on food quality and safety in order to protect animal and human health. Veterinary drugs represent an important risk and the need to have sensitive and fast analytical techniques to detect and quantify them has become mandatory. Over the years, the availability of different modes, interfaces, and formats has improved the versatility, sensitivity, and speed of capillary electrophoresis (CE) techniques. Thus, CE represents a powerful tool for the analysis of a large variety of food matrices and food-related molecules with important applications in food quality and safety. This review focuses the attention of CE applications over the last decade on the detection of different classes of drugs (used as additives in animal food or present as contaminants in food products) with a potential risk for animal and human health. In addition, considering that the different sample preparation procedures have strongly contributed to CE sensitivity and versatility, the most advanced sample pre-concentration techniques are discussed here.

Handheld Inkjet Printing Paper Chip Based Smart Tetracycline Detector

Tetracycline is widely used as medicine for disease treatments and additives in animal feeding. Unfortunately, the abuse of tetracycline inevitably causes tetracycline residue in animal-origin foods. Though classical methods can detect tetracycline in high sensitivity and precision, they often rely on huge and expensive setups as well as complicated and time-consuming operations, limiting their applications in rapid and on-site detection. Here, we propose a handheld inkjet printing paper chip based smart tetracycline detector: tetracycline can be determined by inkjet printing prepared paper chip based enzyme-linked immunosorbent assay (ELISA) with the advantages of high sensitivity, excellent specificity and low cost; moreover, a smartphone based paper chip reader and application is designed for automatically determining tetracycline with simple operations, high precision and fast speed. The smart tetracycline detector with a compact size of 154 mm × 80 mm × 50 mm and self-supplied internal power can reach a rather low detection limit of ~0.05 ng/mL, as proved by practical measurements. It is believed the proposed handheld inkjet printing paper chip based smart tetracycline detector is a potential tool in antibiotic sensing for routine uses at home and on-site detection in the field.

A novel M-shape electrochemical aptasensor for ultrasensitive detection of tetracyclines

Analytical techniques for detection and quantitation of tetracyclines in food products are greatly in demand. In this study, a novel electrochemical aptasensor was designed for ultrasensitive and selective detection of tetracyclines, based on M-shape structure of aptamer (Apt)-complementary strands of aptamer (CSs) complex, exonuclease I (Exo I) and gold electrode. The aptasensor was developed to make a noticeable electrochemical difference in the absence and presence of tetracycline. In the absence of tetracycline, the M-shape structure, which acts as a gate and barrier for the access of redox probe to the surface of gold electrode remains intact, leading to a weak electrochemical signal. Upon addition of tetracycline, Apt leaves CSs, resulting in disassembly of M-shape structure and following the addition of Exo I, a strong electrochemical signal was observed. The developed analytical assay indicated high selectivity toward tetracycline with a limit of detection (LOD) as low as 450 pM. Moreover, the designed aptasensor was effectively used for the detection of tetracycline in milk and serum samples with LODs of 740 and 710 pM, respectively.

Capillary Electrophoresis in Food and Foodomics

Quality and safety assessment as well as the evaluation of other nutritional and functional properties of foods imply the use of robust, efficient, sensitive, and cost-effective analytical methodologies. Among analytical technologies used in the fields of food analysis and foodomics, capillary electrophoresis (CE) has generated great interest for the analyses of a large number of compounds due to its high separation efficiency, extremely small sample and reagent requirements, and rapid analysis. The introductory section of this chapter provides an overview of the recent applications of capillary electrophoresis (CE) in food analysis and foodomics. Relevant reviews and research articles on these topics are tabulated including papers published in the period 2011-2014. In addition, to illustrate the great capabilities of CE in foodomics the chapter describes the main experimental points to be taken into consideration for a metabolomic study of the antiproliferative effect of carnosic acid (a natural diterpene found in rosemary) against HT-29 human colon cancer cells.

A novel colorimetric triple-helix molecular switch aptasensor for ultrasensitive detection of tetracycline

Detection methods of antibiotic residues in blood serum and animal derived foods are of great interest. In this study a colorimetric aptasensor was designed for sensitive, selective and fast detection of tetracycline based on triple-helix molecular switch (THMS) and gold nanoparticles (AuNPs). As a biosensor, THMS shows distinct advantages including high stability, sensitivity and preserving the selectivity and affinity of the original aptamer. In the absence of tetracycline, THMS is stable, leading to the aggregation of AuNPs by salt and an obvious color change from red to blue. In the presence of tetracycline, aptamer binds to its target, signal transduction probe (STP) leaves the THMS and adsorbs on the surface of AuNPs. So the well-dispersed AuNPs remain stable against salt-induced aggregation with a red color. The presented aptasensor showed high selectivity toward tetracyclines with a limit of detection as low as 266 pM for tetracycline. The designed aptasensor was successfully applied to detect tetracycline in serum and milk.

Recent advances in CE analysis of antibiotics and its use as chiral selectors

Antibiotics are a class of therapeutic molecules widely employed in both human and veterinary medicine. This article reviews the most recent advances in the analysis of antibiotics by CE in pharmaceutical, environmental, food, and biomedical fields. Emphasis is placed on the strategies to increase sensitivity as diverse off-line, in-line, and on-line preconcentration approaches and the use of different detection systems. The use of CE in the microchip format for the analysis of antibiotics is also reviewed in this article. Moreover, since the use of antibiotics as chiral selectors in CE has grown in the last years, a new section devoted to this aspect has been included. This review constitutes an update of previous published reviews and covers the literature published from June 2011 until June 2013.

A highly sensitive and selective assay of doxycycline by dualwavelength overlapping resonance Rayleigh scattering

A dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS) method was developed and validated for highly sensitive and selective assay of doxycycline residues in several meat samples. The response signals were dependent on the specific multi-site coordination between lanthanum(III) and doxycycline (DOTC). And La(III)-DOTC complex would further aggregate to form [La(III)-DOTC]n nanoparticles, resulting in the occurrence of two new scattering peaks. Notably, with the addition of DOTC, the increments of both of these two wavelengths were proportional to the concentration of DOTC over the ranges of 3.9-4.0×10(3) nmol L(-1) (1.7-1.8×10(3) μg/kg). The detection limit of DWO-RRS was 1.1 nmol L(-1) (0.5 μg/kg), which was lower than or comparable to most of the published methods. Additionally, the generating mechanisms of multi-response RRS signals were discussed and a semi-empirical principle was established for better design of multi-response RRS probes.