Detection Of Tetracycline Research Articles

Copper nanoclusters modified molybdenum disulfide quantum dots probe for sensitive detection of tetracycline

By combining molybdenum disulfide quantum dots (MoS2 QDs) synthesized using a facile hydrothermal method with copper nanoclusters (Cu NCs), copper-ion-modified molybdenum disulfide probes (Cu-MoS2 QDs) were obtained, enabling sensitive detection and specific recognition of tetracycline (TET). The synthesized probes were characterized using techniques such as fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The fluorescence values of the probes and TET after their reaction at different concentrations were used to calculate a detection limit of 30 nM for the synthesized probes. The recovery rate of actual samples reached a high value of 95.70%, with a relative standard deviation below 2.00%, demonstrating excellent accuracy and precision. The probe exhibited high selectivity towards TET. The accuracy is maximized when the concentration of the probe is 4.50 × 10−5 mol/L, indicating enhanced performance of the molybdenum disulfide probe after copper ion modification and obtaining favorable detection outcomes. This probe holds great potential in enhancing the safety of animal-derived food, ensuring public health, and preserving water resources.

Sodium dodecyl sulfate-modified ZIF-8 for sensitive detection of tetracycline in foods under synergistic adsorption of sodium dodecyl sulfate

The abuse for tetracycline (TC) in animal husbandry causes the residue of TC in animal foods, and even in vegetables arised from the pollution of soil. The sensitive determination of TC is greatly significant for the safety monitoring of foods. Herein, sodium dodecyl sulfate (SDS) was self-assembled on zeolite imidazolate framework-8 (ZIF-8) via hydrophobic interaction. The sensitive fluorescent detection of TC was obtained based on ZIF-8@SDS as-synthesized. After adding TC to ZIF-8@SDS, the internal ZIF-8 sensitized the emission band of TC centered at 521 nm, and the external SDS adsorbed TC via hydrophobic and electrostatic interactions. On this basis, TC could be quantified by ZIF-8@SDS selectively in a concentration range from 0.01 to 60 μM within 1 min. Importantly, the synergistic adsorption effect of SDS promoted the sensitivity of ZIF-8@SDS, and the limit of detection as low as 9 nM was calculated toward TC. The concentrations of TC in fish and tomato samples were determined by ZIF-8@SDS. The relative standard deviations ranged from 1.1 % to 6.7 %, and the spiked recoveries were in the range of 85.2 %–116.2 %, proving the application potential of ZIF-8@SDS in food safety monitoring.

A ratiometric dual-fluorescent paper-based synthetic biosensor for visual detection of tetracycline on-site

The excessive use of tetracycline poses a threat to human health, making it essential to monitor and regulate its usage. While whole-cell biosensors offer a simple and cost-effective method, their utility is constrained by limitations in sensitivity, portability, and robustness, hindering real-time measurements within complex environmental contexts. In this study, a ratiometric i/cTetR synthetic biosensing test strip with an engineered modified dual-fluorescence reporting was developed for detecting Tet antibiotics in water and food. First, the standardized unidirectional promoter PtetR by tailoring and screening TetR transcription factor binding sites and verified by molecular docking, shortening the detection time. Secondly, decoupling the sensing and reporting modules enhances the biosensor's performance, eliminating genetic background leakage and tripling the output signal. Thirdly, a ratiometric dual fluorescence signal i/cTetR biosensing test strip was designed. Under the light box LED/UV light source, the dual signal output method significantly reduced false negative results and enhanced the anti-interference capability of the biosensor. The i/cTetR strips can detect Tet in tap water (5–1280 μg/mL) and milk (50–3200 μg/kg) within 45 min in high volume on-site without separation and purification. This study provides a standardized and universal sensing method for the field detection of antibiotic contaminants.

Engineering Assembly of Plasmonic Virus-Like Gold SERS Nanoprobe Guided by Intelligent Dual-Machine Nanodevice for High-Performance Analysis of Tetracycline.

Accurate detection of trace tetracyclines (TCs) in complex matrices is of great significance for food and environmental safety monitoring. However, traditional recognition and amplification tools exhibit poor specificity and sensitivity. Herein, a novel dual-machine linkage nanodevice (DMLD) is proposed for the first time to achieve high-performance analysis of TC, with a padlock aptamer component as the initiation command center, nucleic acid-encoded multispike virus-like Au nanoparticles (nMVANs) as the signal indicator, and cascade walkers circuit as the processor. The existence of spike vertices and interspike nanogaps in MVANs enables intense electromagnetic near-field focusing, allowing distinct surface-enhanced Raman scattering (SERS) activity. Moreover, through the sequential activation between multistage walker catalytic circuits, the DLMD system converts the limited TC recognition into massive engineering assemblies of SERS probes guided by DNA amplicons, resulting in synergistic enhancement of bulk plasmonic hotspot entities. The continuously guaranteed target recognition and progressively promoted signal enhancement ensure highly specific amplification analysis of TC, with a detection limit as low as 7.94 × 10-16g mL-1. Furthermore, the reliable recoveries in real samples confirm the practicability of the proposed sensing platform, highlighting the enormous potential of intelligent nanomachines for analyzing the trace hazards in the environment and food.

Conjugation of tetracycline with carrier proteins and production of its polyclonal antibody for the development of rapid test

Tetracycline (TC) is a broad-spectrum antibiotic used in the treatment of several infectious diseases. The excessive use of tetracycline antibiotics, especially tetracyclines in livestock, has raised concerns about residues of tetracycline antibiotics in food that may affect consumers' health. It is necessary to develop a rapid test strip for detecting tetracycline antibiotic residues in food and animal feed. This paper presents the suitable conditions for the conjugation of tetracycline to BSA or KLH: molar ratio of TC:BSA/KLH was 25:1, formaldehyde concentration of 5 %, temperature of 4oC and reaction time of 4 hours. The KLH-TC conjugate was used to successfully raise polyclonal antibodies against TC in rabbits. The anti-TC polyclonal antibodies were purified and could be used for the development of the lateral flow immunoassay test strip for the detection of tetracycline.

Detection of tetracycline and ampicillin resistant E. coli and Salmonella species from hospital wastewater

Escherichia coli (E. coli) and Salmonella spp. were found in hospital wastewater. The highest (E = (6.2 ± 1.8) x 109; S = (4.3 ± 2.2) x 109) and lowest (E = (1.4 ± 1.2) x 109; S = (1.1 ± 1.8) x 109) Total Viable Count (TVC) were in Shaheed Suhrawardy Medical College Hospital (SSMCH) and National Institute of Ophthalmology Hospital (NIOH), respectively. The overall occurrence of E. coli and Salmonella spp. was 80% and 87%, respectively, with 100% occurrence in SSMCH and National Institute of Cardiovascular Diseases Hospital (NICVDH) for Salmonella spp. (p ≤ 0.036). Prevalence of E. coli was low (72%) in winter (November - February). Both types of bacteria were resistant to Tetracycline whereas and 97.5% of E coli were resistant to ampicillin. Gentamycin was more effective than other antibiotics. Rational use of antibiotics is suggested, and hospital management practice should be followed as defined by the Joint Commission International for Hospital Accreditation.
 Bang. vet. 2023. Vol. 40, No. 1 – 2, 16 – 24

Highly sensitive dual-mode assay for tetracycline detection

A dualmode tetracycline (TC) assay was developed based on a colloidally stable mixture of TC-specific aptamer stabilized AuNPs (Apt-stabilized AuNPs) and graphite carbon nitride nanosheets (g-C3N4) for sensitive detection of TC. The presence of TC in the solution could be identified based on the colorimetric and fluorescent signals. This dual-mode assay requires no salt during TC detection and has high sensitivity, allowing detection limits (LOD) of TC to 1.0 × 10−16 M with a wide dynamic detection range (six orders of magnitude, from 5.0 × 10−16 to 5.0 × 10−11 M), and exhibits good selectivity for TC over other metal cations, antibiotics, amino acids, and proteins. The mechanism of this dual-mode assay for TC detection was investigated in detail. Moreover, the amount of TC in actual samples (spiked drinking water and milk) was successfully monitored. The findings provide valuable guidance in developing an advanced platform for detecting TC and other antibiotics.

A miniaturized biosensor for rapid detection of tetracycline based on a graphene field-effect transistor with an aptamer modified gate

Tetracycline is a broad-spectrum antibiotic for human, poultry and livestock that may cause health damage when enriched in humans. Therefore, it is essential to create a rapid tetracycline assay with high sensitivity, specificity and portability. In this study, a miniaturized tetracycline biosensor based on aptamer-modified graphene field-effect transistor (Apt-SGGT) was fabricated and two detection strategies using transfer characteristic curves and real-time channel current were established for different circumstances. The detection limits of the two strategies were 2.073 pM and 100 pM, respectively. The biosensor also demonstrated outstanding stability, anti-interference and specificity ability. Finally, the biosensor was employed to detect the content of tetracycline in Skim Milk with outstanding recovery rate. We believe that the miniaturized Apt-SGGT biosensor with appropriate detection strategies will provide an ideal portable sensing platform for many important analytes in food with superior selectivity and sensitivity.

Aggregation-induced emission carbon dots as Al3+-mediated nanoaggregate probe for rapid and selective detection of tetracycline

Worldwide abuse of tetracycline (TC) seriously threatens environmental safety and human health. Metal-TC complexes formed by residual TC in the environment can also contribute to the spread of antibiotic resistance. Therefore, monitoring of TC residues is still required. Here, we report novel aggregation-induced emission carbon dots (AIE-Cdots) as nanoaggregate probes for the rapid and selective detection of TC residue. Riboflavin precursors with rotational functional groups led to the development of AIE-Cdots. The aggregation of AIE-Cdots was induced selectively for Al3+, amplifying the fluorescence signals owing to the restricted rotation of the side chains on the AIE-Cdot surface. The fluorescence signal of such Al3+-mediated nanoaggregates (Al3+-NAs) was further triggered by the structural fixation of TC at the Al3+ active sites, suggesting the formation of TC-coordinated Al3+-NAs. A linear correlation was observed in the TC concentration range of 0–10 μM with a detection limit of 42 nM. In addition, the strong Al3+ binding affinity of AIE-Cdots produced similar NAs and enhanced fluorescence signals in Al3+–TC mixtures. These AIE-Cdots-based nanoplatforms have a rapid response, good selectivity, and reliable accuracy for detecting TC or aluminum complexes, meeting the requirements for hazardous substance monitoring and removal in environmental applications.

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

BackgroundTetracycline (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. ResultsA 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. SignificanceThe 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.

Novel electrochemical/fluorescence dual-mode biosensor based on covalent organic framework for tetracycline detection

Excessive antibiotic residues increased the environmental damage and safety of animal products, leading to serious health threats. In this study, a dual-mode probe was developed and applied as an electrochemical/fluorescence sensor for tetracycline (TET) detection. The probe, comprising a fluorescent covalent organic framework, electroactive methylene blue, gold nanoparticles (AuNPs) and single-stranded DNA, was synthesized by self-assembly. A glassy carbon electrode was functionalized with molybdenum disulfide nanosheets, AuNPs, and aptamers. The probe exhibited fluorescent signals in solution and electrochemical signals after being specifically connected to the electrode via hybridization. In the presence of TET, the probe is be competitively expelled from the modified electrode, resulting in an increase in the fluorescent signal and a decrease in the electrochemical signal. The developed electrochemical/fluorescence dual-mode sensor enabled sensitive TET detection in the concentration range of 10 nM–10 mM, with minimum detection limits of 0.03 nM (electrochemical) and 0.05 nM (fluorescence). With its high selectivity, superior reproducibility, and excellent stability, the proposed dual-mode sensor demonstrates high reliability, and excellent application prospects for TET detection in milk and river water samples.

L-arginine and 1,4-Butanediol conjugated highly ordered nitrogen doped carbon dots as photoluminescent probe for “turn off” based detection of organic pollutants in real sample matrices

Nitrogen doped carbon dots are emerging as efficient photoluminescent probes for wide range of sensing applications. A simple strategy of synthesizing highly ordered nitrogen doped carbon dots (named here as N-CDarg) is developed by thermal conjugation of 1, 4-Butanediol with L-Arginine. It led to formation of self-assembled transverse carbon chains through oligomerization of 1,4-Butanediol and conjugation with L-Arginine. The structural, morphological and compositional analysis of the N-CDarg is confirmed from 1H and 13C NMR, mass spectroscopy, FT-IR, higher resolution transmission electron microscopy and X-ray photoelectron spectroscopy. It exhibited bright bluish photoluminescence with PL quantum yield of 11 %. Under optimized pH and contact time, the probe solution of N-CDarg exhibited dual sensing for the detection of tetracycline (TC) and 4-nitrophenol (4-NP) via PL quenching proportional, which followed Stern-Volmer relation. The linear PL quenching response for TC is in the range of 0.5 μM to 60 μM with a limit of detection (LOD) of 103 nM; while the linear range for 4-NP is 0.4 μM to 20 μM, and the LOD is 77 nM. Selectivity of these species have been confirmed against several metal ions, anions, other antibiotics (for TC detection) and different structural analogues of phenols (for 4-NP detection). The ability of the probe to quantitatively detect trace concentrations of TC and 4-NP in real sample matrices like river water and milk has been demonstrated by spike analysis. The mechanism of PL quenching of N-CDarg by TC and 4-NP has been discussed using PL decay lifetime spectroscopy.

A bioluminescence method based on NLuc-TetR for the detection of nine Tetracyclines in milk

Trace antibiotic residues in animal foodstuff may lead to resistance and hazard human health, so simple and rapid detection methods have aroused multiple attention. Here, a novel bioluminescence pseudo-ELISA for the trace detection of multiple tetracyclines (TCs) in milk was designed and prepared based on a new fusion protein NLuc-TetR. The N-terminal of the bio-recognition motif TetR was linked to the C-terminal of the reporting motif nano-luciferase (NLuc) through SOE-PCR. Biolumescence signal showed that NLuc-TetR was specificity to nine TCs. And the acting pattern of substrate, NLuc-TetR, and TCs ternary complex was analyzed by molecular docking. With the optimal parameters, the half inhibition concentrations (IC50) of the developed bioluminescence pseudo-ELISA for nine TCs ranged from 0.39 to 1.44 ng mL−1, and the detection limits (LODs) ranged from 2 to 11 pg mL−1. The results demonstrated that the bioluminescence method based on NLuc-TetR is a promising method for routine screening measures for the residues of TCs in milk.

A novel biosensor based on antibody-controlled strand displacement amplification (SDA) and hybridization chain reaction (HCR) for tetracycline detection

The specificity of antibodies and efficient amplification of nucleic acid molecules play an important role in developing biosensors for monitoring human and environmental health. Herein, integrating their capabilities by site-selective modification of small molecules on DNA, a biosensor based on antibody-controlled strand displacement amplification (SDA) and hybridization chain reaction (HCR) was developed. The SDA–HCR reaction was activated by the competitive binding of antibodies to free small molecules and small molecule-conjugated DNA. As a proof-to-concept, we developed a biosensor capable of detecting tetracycline (TC) with high sensitivity and specificity. First, TC was labeled with azide group through chemical modification, and TC–DNA was prepared by copper-free click chemistry. Further, the antibody-controlled SDA–HCR reaction was developed through serial optimization. By this method, TC could be detected in a linear range of 0.01–100 µM with a detection limit of 0.006 µM, and the recovery of actual samples was 96.62–100.31 % with 1.70–4.00 % RSD, suggesting satisfactory performance by the biosensor. Using this method, TC or any other small molecules can be detected without washing, immobilization, and multiple additional steps, which would simplify detection to a great degree. Consequently, the distinctive strategy proposed in this work may find more applications in the detection of other small molecules.

Sense and Shoot: Multifunctional CaO2-loaded Cu-MOF nanosheets for integrated fluorescence detection and fenton-like degradation of tetracycline

Simultaneous accomplishment of sensitive detection and efficient degradation of antibiotics residues exposed in the aqueous environments has proved to be a difficult endeavor. Here, multifunctional composite CaO2-loaded Cu-MOF nanosheets (CaO2@Cu-MOF NSs) was elaborately designed and synthesized. Triggered by H+, the composite is not only capable of producing Ca2+ as the signal factor for tetracycline (TC) detection by activating the fluorescence emission of calcein, but also capable of self-supplying H2O2 and Cu2+ to construct a novel Fenton-like oxidation and O2 activation system for TC degradation based on Cu2+/Cu+ cycle. Under the synergy of target cycling and nano-enhancement, the sensing system exhibited great TC detection performance with a linear range of 0.001 to 100 ng mL−1 and detection limit of 11.8 fg mL−1. At the same time, the degradation system exhibited favorable degradation performance under the systematic action of Fenton-like and O2-activated oxidation. Nearly 80 % of the TC residues could be degraded within 10 min, and more than 95 % within 60 min. The constructed system was successfully applied to detect and degrade exposed TC in actual water samples in an integrated manner, demonstrating great promise for practical applications.

An enzyme-free and label-free ratiometric fluorescence signal amplification biosensor based on DNA-silver nanoclusters and catalytic hairpin assembly for tetracycline detection

Sensitive and accurate in antibiotic detection is crucial for food security, environmental conservation, public health, and environmental protection. In this study, we developed an enzyme-free and label-free ratiometric fluorescence biosensor for highly sensitive detection of tetracycline (TET). This biosensor utilized a combination of target-triggered catalytic hairpin assembly (CHA) and DNA-silver nanocluster (DNA-AgNCs) dual-color fluorescent signal probes. Upon TET binding to the aptamer, it initiated the leakage of CHA initiator, resulting in the formation of numerous double-stranded DNA complexes. This process exposed the foothold sequence of hairpin-structured DNA-AgNCs (H3-AgNCs) that exhibit yellow fluorescence. Subsequently, the conformational changes in H3-AgNCs significantly reduced the yellow fluorescence intensity (FI) and reveal the auxiliary DNA-AgNCs (a-DNA-AgNCs) linkage sequence. The binding of a-DNA-AgNCs brought two dark AgNCs close, forming nanocluster dimers emitting red fluorescence. The results demonstrate that the variation in ratiometric signal is linear with TET concentration between 0.1 and 50 ng/mL, with a detection limit as low as 0.086 ng/mL. Additionally, this approach exhibited good recovery results with spiked milk samples. This enzyme-free and label-free combined signal amplification method with proportional signal output based on DNA-AgNCs provides valuable empirical reference for creating low-cost, stable, and highly-sensitive biosensors.

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

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

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

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

Multi-drug resistant (MDR) Gram-negative pathogenic bacteria isolated from poultry in the Noakhali region of Bangladesh.

Rapidly increasing antibiotic-resistant bacterial strains in Bangladesh's food and farm animals stem from the excessive and inappropriate use of antibiotics. To assess the prevalence of multi-drug resistant (MDR) Gram-negative bacteria in poultry chicks, we sought to isolate and identify strains carrying antimicrobial resistance genes. Isolation and identification involved biochemical tests, 16S rRNA sequencing, and PCR screening of species-specific genes. MDR patterns were evaluated using CLSI guidelines with seventeen antibiotics across twelve classes. Targeted gene sequences were amplified for the detection of Extended-spectrum β-Lactamase (ESBL), carbapenem, tetracycline, sulfonamide, and colistin resistance genes. Common isolates, such as Escherichia coli, Klebsiella pneumoniae, Proteus penneri, and Enterobacter hormaechei, exhibited average Multiple Antimicrobial Resistance (MAR) indices of 0.66, 0.76, 0.8, 0.84, and 0.81, 0.76, 0.84, 0.41 for broiler and layer chicken, respectively. Providencia stuartii and Salmonella enterica, exclusive to broiler samples, had MAR indices of 0.82 and 0.84, respectively. Additional isolates Morganella morganii, Aeromonas spp., and Wohlfahrtiimonas chitiniclastica were found in layers (Average MAR indices: 0.73, 0.71, and 0.91). Notably, M. morganii, E. hormaechei and W. chitiniclastica were identified for the first time in Bangladeshi poultry chicken, although their evolution is yet to be understood. In this study, Pan-drug resistance was observed in one P. stuartii (broiler) and one Aeromonas spp. (layer) with a MAR index 1, while all isolates exhibited MAR indices >0.2, indicating MDR. Antimicrobial resistance (AMR) gene screening identified blaTEM, blaSHV, tetA, and sul1 in a majority of the MDR strains. Interestingly, E. coli (lactose positive and negative) and E. hormaechei were exclusively found to possess the tetB gene. In addition, E. coli (lactose negative), Klebsiella pneumoniae, Enterobacter hormaechei, M. morganii, and P. stuartii were observed to carry the colistin-resistant mcr-1 gene, whereas sul2 was detected in E. coli (lactose positive and negative), E. hormaechei, P. stuartii, and P. penneri. These findings emphasize the health risk of our consumers of both broiler and layer chickens as they have turned into a potent reservoir of various AMR gene carrying MDR and Pan-drug resistant bacteria.

A paper-based ratiometric fluorescence sensor based on carbon dots modified with Eu3+ for the selective detection of tetracycline in seafood aquaculture water.

Paper-based ratiometric fluorescence sensors are normally prepared using two or more types of fluorescent materials on a paper chip for simple, low-cost and fast detection. However, the choice of multi-step and one-step modifications on the paper chip affects the analytical performance. Herein, a novel paper-based dual-emission ratiometric fluorescence sensor was designed for the selective detection of tetracycline (TC). Carbon dots (CDs) modified with Eu3+ were combined with a sealed paper-based microfluidic chip by two methods: one-step grafting of CDs-Eu3+ on paper and step-by-step grafting of CDs and Eu3+ on paper. The analytical performance was studied and optimized respectively. The red fluorescence of Eu3+ at 450 nm is enhanced and the blue fluorescence of CDs at 617 nm is quenched by energy transfer in the presence of TC. Under optimal conditions, TC is selectively determined in the linear range from 0.1 μM to 100 μM with a detection limit of 0.03 μM by the step-by-step grafting method. In addition, the sealed paper chip could effectively prevent pollution and volatilization from the reagent. This technique has been used to analyze TC in seafood aquaculture water with satisfactory results.