Recent advances in luminescence and aptamer sensors based analytical determination, adsorptive removal, degradation of the tetracycline antibiotics, an overview and outlook

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.

Ratiometric fluorescence sensor based on deep learning for rapid and user-friendly detection of tetracycline antibiotics

The detection of tetracycline antibiotics (TCs) in food holds great significance in minimizing their absorption within the human body. Hence, this study aims to develop a rapid, convenient, real-time, and accurate detection method for detecting antibiotics in an authentic market setting. A colorimetric fluorescence sensor was devised for tetracycline detection utilizing PVA aerogels as the substrate. Its operating principle is based on the IFE effect and antenna effect. A detection device is designed to capture fluorescence images while deep learning was employed to aid in the detection process. The sensor exhibits high responsiveness with a mere 60-s requirement for detection and demonstrates substantial color changes(blue to red), achieving 99% accuracy within the range of 10-100 μM with the assistance of deep learning (Resnet18). Real sample simulation tests yielded recovery rates between 95% and 130%. Overall, the proposed strategy proved to be a simple, portable, reliable, and responsive solution for rapid real-time TCs detection in food samples.

Colorimetric aptasensor utilizing MOF-235 with exceptional peroxidase-like activity for the detection of oxytetracycline residues in raw milk

In this work, a simple, convenient and cost-effective colorimetric aptasensor was successfully constructed for the detection of antibiotic residues in raw milk based on the property that aptamer (Apt) synergistically enhances the catalase-like activity of MOF-235. Under optimised conditions, the proposed colorimetric aptasensor exhibited a wide detection range (15-1500 nM) with a low detection limit (6.92 nM). Furthermore, the proposed aptasensor demonstrated high selectivity, good resistance to interference and storage stability. The proposed aptasensor was validated by spiking recovery in camel milk, cow milk and goat milk with satisfactory recoveries, which demonstrated the great potential of the aptasensor for further application in real food samples, and also suggested that MOF-235 can be used as a potential universal platform to build a sensitive detection platform for other targets.

Microbial Degradation of Tetracycline Antibiotics: Mechanisms and Environmental Implications

The escalating global consumption of tetracyclines (TCs) as broad-spectrum antibiotics necessitates innovative approaches to mitigate their pervasive environmental persistence and associated risks. While initiatives such as China's antimicrobial reduction efforts highlight the urgency of responsible TC usage, the need for efficient degradation methods remains paramount. Microbial degradation emerges as a promising solution, offering novel insights into degradation pathways and mechanisms. Despite challenges, including the optimization of microbial activity conditions and the risk of antibiotic resistance development, microbial degradation showcases significant innovation in its cost-effectiveness, environmental friendliness, and simplicity of implementation compared to traditional degradation methods. While the published reviews have summarized some aspects of biodegradation of TCs, a systematic and comprehensive summary of all the TC biodegradation pathways, reactions, intermediates, and final products including ring-opening products involved with enzymes and mechanisms of each bacterium and fungus reported is necessary. This review aims to fill the current gap in the literature by offering a thorough and systematic overview of the structure, bioactivity mechanism, detection methods, microbial degradation pathways, and molecular mechanisms of all tetracycline antibiotics in various microorganisms. It comprehensively collects and analyzes data on the microbial degradation pathways, including bacteria and fungi, intermediate and final products, ring-opening products, product toxicity, and the degradation mechanisms for all tetracyclines. Additionally, it points out future directions for the discovery of degradation-related genes/enzymes and microbial resources that can effectively degrade tetracyclines. This review is expected to contribute to advancing knowledge in this field and promoting the development of sustainable remediation strategies for contaminated environments.

Ratiometric fluoroprobe based on Eu-MOF@Tb3+ for detecting tetracycline hydrochloride in freshwater fish and its application in rapid visual detection

Tetracycline hydrochloride (TCH), a prevalent antibiotic in aquaculture for treating bacterial infections, poses challenges for on-site detection. This study employed the reversed-phase microemulsion method to synthesize a uniform nano metal-organic framework (MOF) material, europium-benzene-p-dicarboxylic acid (Eu-BDC), doped with Tb3+ to form a dual-emission fluorescence probe. By leveraging the combined a-photoinduced electron-transfer (a-PET) and inner filter effect (IFE) mechanisms, high-sensitivity TCH detection in Carassius auratus and Ruditapes philippinarum was achieved. The detection range for TCH is 0.380-75 μM, with a low limit of detection (LOD) at 0.115 μM. Upon TCH binding, Eu-BDC fluorescence rapidly decreased, while Tb3+ fluorescence remained constant, establishing a ratiometric fluorescence change. Investigation into the TCH quenching mechanism on Eu-BDC was conducted using time-dependent density functional theory (TD-DFT) calculations and fluorescence quenching kinetic equations, suggesting a mixed quenching mechanism. Furthermore, a novel photoelectric conversion fluorescence detection device (FL-2) was developed and evaluated in conjunction with high-performance liquid chromatography-diode-array detection (HPLC-DAD). This is the first dedicated fluorescence device for TCH detection, showcasing superior photoelectric conversion performance and stability that reduces experimental errors associated with smartphone photography methods, presenting a promising avenue for on-site rapid TCH detection.

Zinc(II)-MOF: A Versatile Luminescent Sensor for Selective Molecular Recognition of Flame Retardants and Antibiotics

An exceptional Zinc(II)-organic framework with the formula [{Zn(L4-py)(bdc)}·DMF]n (Zn-MOF) has been constructed solvothermally using a novel linker L4-py {2,7-bis(3-(pyridin-4-ylethynyl)phenyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone}, coligand H2bdc (1,4-benzenedicarboxylic acid), and ZnBF4·xH2O. The ligand L4-py has been fabricated after functionalization of NDA (1,4,5,8-naphthalenetetracarboxylic dianhydride) core with 3-(pyridin-4-ylethynyl)phenyl group. The single-crystal X-ray analysis reveals that Zn-MOF exhibits a comprehensive three-dimensional (3D) framework architecture and features (4)-connected uninodal dia; 4/6/c1; sqc6 topology with point symbol {66} and two-dimensional (2D) + 2D, parallel polycatenation. Notably, Zn-MOF displayed excellent fluorescence phenomenon and stability in water as well as in methanol solvents and was harnessed as a versatile sensor, demonstrating selective and sensitive molecular recognition of flame retardants and antibiotics. Notably, Zn-MOF displayed 57 and 49.5% quenching efficiency for the flame-retardant pentabromophenol (PBP) and 3,3',5,5'-tetrabromobisphenol A (TBPA), respectively. Whereas an outstanding 90% quenching efficiency was observed for antibiotics, tetracycline (TC) and secnidazole (SD). The mechanistic investigations of this luminescence quenching suggest that this might be primarily occurring via the Fourier resonance energy transfer (FRET) and photoinduced electron transfer (PET) mechanisms, which might be assisted by the competitive absorption and host-guest interactions. The π-electron-rich framework structure of sensor Zn-MOF activates this mechanism.

Fluorescent and smartphone imaging detection of tetracycline residues based on luminescent europium ion-functionalized the regular octahedral UiO-66-NH2

Antibiotic residues cause extensive damage to food security, thus arousing serious concerns. Hence, rapid and sensitive detection of antibiotic residues is crucial to food safety. This study aimed to propose a portable, visual, intelligent and rapid method for tetracycline detection. We developed a ratiometric fluorescent sensor based on the Eu3+-functionalized regular octahedral UiO-66-NH2 material. The developed sensor could quantify tetracycline in the concentration range of 0.5-200 μM with a detection limit as low as 0.2 μM under the optimum conditions. Furthermore, the analytical results obtained using the designed sensor in the actual samples were basically consistent with those obtained using high-performance liquid chromatography. Based on these achievements, a smartphone application-integrated fluorescent testing paper was designed for facile, intelligent, and visual detection of tetracycline. The integrated portable sensor not only saved cost and time for testing but also provided a forward-looking approach to fast, sensitive detection of antibiotic residues.

Ultrafast and simultaneous removal of four tetracyclines from aqueous solutions using waste material-derived graphene oxide-supported cobalt-iron magnetic nanocomposites

In this work, a graphene oxide-supported cobalt-iron oxide (GO/Co-Fe) magnetic nanocomposite was successfully synthesized using waste dry cells for the efficient and simultaneous removal of tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC), and doxycycline (DTC) from aqueous solutions. The GO/Co-Fe nanocomposite was thoroughly characterized using Fourier transform infrared spectroscopy, vibrating sample magnetometry, X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and zeta potential analysis. This multi-faceted characterization provided clean insights into the composition and properties of the synthesized nanocomposite. The adsorption of tetracyclines (TCs) was systematically investigated by assessing the influence of critical factors, such as adsorbent dosage, contact duration, initial pH of the solution, initial concentration, and temperature. The GO/Co-Fe adsorbent showed high removal efficiencies of 94.1% TC, 94.32% CTC, 94.22% OTC, and 96.94% DTC within 30 s contact period. The maximum removal efficiency of TCs was found at a low adsorbent dose of 0.15 g L-1. Notably, this superior removal efficiency was achieved at neutral pH and room temperature, demonstrating the adsorbent's efficacy under environmentally viable conditions. The kinetic studies demonstrated that the adsorption process was fitted satisfactorily with the pseudo-second-order model. Additionally, the adsorption behaviour of TCs on the GO/Co-Fe adsorbent was assessed by isotherm models, Langmuir and Freundlich. The experimental data followed the Langmuir isotherm, signifying a monolayer adsorption mechanism on the surface of the adsorbent. The adsorption capacities (qm) of GO/Co-Fe for TC, CTC, OTC and DTC were determined to be 64.10, 71.43, 72.46 and 99.01 mg g-1, respectively. Importantly, the GO/Co-Fe adsorbent showed reusability capabilities. The super magnetic properties of GO/Co-Fe made it easy to use for several cycles. These results clearly establish GO/Co-Fe as an exceptionally effective adsorbent for the removal of TCs from aqueous systems, highlighting its great potentiality in water treatment applications.

An indirect competitive assay-based method for the sensitive determination of tetracycline residue using a real-time fluorescence-based quantitative polymerase chain reaction

Tetracycline (TC) is an effective antibiotic used to treat humans and livestock, but its inappropriate use imposes toxic effects, including pollution, on environmental ecology and food. Currently, sensitive, accurate, and cost-effective methods that can detect lower concentrations of TC residues in environmental and food samples are needed. In this study, a novel indirect competitive assay-based aptamer method was developed for detecting TC residues through signal amplification by real-time fluorescence-based quantitative polymerase chain reaction. The response surface methodology was introduced to optimize the optimal concentrations (influencing factors) of the three types of single-stranded DNA in the competitive assay process. The optimal conditions for the three types of ssDNA were 112 nM for the specific aptamer of TC (Apt40), 115 nM for the signal DNA, and 83 nM for the DNA catcher. As expected, under optimal conditions, the Ct value was linearly related to the logarithm of TC concentration. The calibration curve equation was Ct = -0.34516 log[TC] + 9.9345 (R2 = 0.998) in the range of 10-3-103 ng mL-1, and the limit of detection was 7.02 × 10-5 ng mL-1. The new method was effectively applied to detect TC residues in wastewater, honey, and milk samples. It achieved an average recovery rate of 101.19% with a small variation of 5.16%. The validation was carried out using an enzyme-linked immunosorbent assay. This approach demonstrates high sensitivity and selectivity, making it well suited for detecting leftover antibiotics in food when using suitable aptamers.

Metal-organic frameworks (MOFs) based luminescent and electrochemical sensors for food contaminant detection

With the increasing population, food toxicity has become a prevalent concern due to the growing contaminants of food products. Therefore, the need for new materials for toxicant detection and food quality monitoring will always be in demand. Metal-organic frameworks (MOFs) based on luminescence and electrochemical sensors with tunable porosity and active surface area are promising materials for food contaminants monitoring. This review summarizes and studies the most recent progress on MOF sensors for detecting food contaminants such as pesticides, antibiotics, toxins, biomolecules, and ionic species. First, with the introduction of MOFs, food contaminants and materials for toxicants detection are discussed. Then the insights into the MOFs as emerging materials for sensing applications with luminescent and electrochemical properties, signal changes, and sensing mechanisms are discussed. Next, recent advances in luminescent and electrochemical MOFs food sensors and their sensitivity, selectivity, and capacities for common food toxicants are summarized. Further, the challenges and outlooks are discussed for providing a new pathway for MOF food contaminant detection tools. Overall, a timely source of information on advanced MOF materials provides materials for next-generation food sensors.