Concentrations Of Chloramphenicol Research Articles

Synergistic effect on simultaneous treatment of Cr(VI) and chloramphenicol using a non-thermal plasma technology

Toxic organic and heavy metal contaminants commonly exist in industrial waste stream and the treatment is of great challenge. In this study, a dielectric barrier discharge (DBD) non-thermal plasma was employed for the simultaneous treatment of two important contaminants, chloramphenicol (CAP) and Cr(VI) in an aqueous solution through redox transformations. More than 70% of CAP and 20% of TOC were degraded in 60 min, while Cr(VI) was completely removed in 10 min. The hydroxyl radicals could be the main active species for the degradation. Meanwhile, the consumption of hydroxyl radicals was beneficial to the reduction of Cr(VI). The synergistic effect was investigated between CAP degradation and Cr(VI) reduction. The reduction of Cr(VI) would be enhanced in the presence of CAP with a low concentration and could be inhibited under a high concentration of CAP, because part of hydroxyl radicals could be consumed by a low concentration of CAP and the obtained intermediates with a higher kinetic rate. However, CAP with a high concentration could also react with some reductive species, such as eaq- and •H, which could compete with Cr(VI) and inhibit the reduction of Cr(VI). In addition, the presence of Cr(VI) could enhance the degradation and mineralization of CAP, and the identification of obtained intermediates indicated that the presence of Cr(VI) could change the degradation path of CAP as Cr(VI) would react with reductive species and enhance the generation of hydroxyl radicals, leading to more hydroxylation reactions. Moreover, the mechanism for the simultaneous redox transformations of CAP and Cr(VI) was illustrated. This study indicates that the DBD non-thermal plasma technology could be one of better solutions for simultaneous elimination of heavy metal and organic contaminants in aquatic environment.

A facile electrochemical aptasensor for chloramphenicol detection based on synergistically photosensitization enhanced by SYBR Green I and MoS2

This study described the development of a photocatalytic electrochemical aptasensor for the purpose of detecting chloramphenicol (CAP) antibiotic residues in water by utilizing SYBR Green I (SG) and chemically exfoliated MoS2 (ce-MoS2) as synergistically signal-amplification platforms. The Au nanoparticles (AuNPs) were electrodeposited onto the surface of an indium tin oxide (ITO) electrode. After that, the thiolate-modified cDNA, also known as capture DNA, was combined with the aptamer. Subsequently, photosensitized SG molecules and ce-MoS2 nanomaterial were inserted into the groove of the resultant double-stranded DNA (dsDNA). The activation of the photocatalytic process upon exposure to light resulted in the generation of singlet oxygen. This singlet oxygen effectively splits the double-stranded DNA, resulting in a significant enhancement in the current of [Fe(CN)6]3-/4-. When the CAP was present, both SG molecules and ce-MoS2 broke away from the double-stranded DNA, which turned off the photosensitization response, leading to a significant decrease in the current of [Fe(CN)6]3-/4-. Under optimal conditions, the aptasensor exhibited a linear relationship between CAP and logarithmic concentrations from 20 to 1000 nM, with a detection limit (3σ) of 3.391 nM. The aptasensor also demonstrated good selectivity towards CAP in the presence of interfering antibiotics such as tetracycline, streptomycin, levofloxacin, ciprofloxacin, and sulfadimethoxine. Additionally, the results obtained from the analysis of natural water samples using the proposed aptasensor were consistent with the findings acquired through the use of a liquid chromatograph-mass spectrometer. Therefore, with its simplicity and high sensitivity, this biosensor can potentially detect alternative antibiotics in environmental water samples by replacing the aptamers based on photosensitization.

A Physical Insight of Phase-Dependent Electron Transfer Kinetic Behaviors and Electrocatalytic Activity of an Iron Oxide-Based Sensing Nanoplatform Towards Chloramphenicol

Insight into the phase-dependent electron transfer kinetics and electrocatalytic activity of metal oxide nanostructures is important in the rational design of functional nanostructures for realizing high-performance electrochemical sensors. This study focuses on elucidating the effect of the crystalline phase on the electron transfer kinetics and electrocatalytic activity of iron(III) oxide. The α-FeOOH, γ-Fe2O3, and α-Fe2O3 nanorods were designed by using a simple chemical method and calcining process. The phase-dependent difference in the electron transfer kinetics and electrocatalytic activity toward the sensitive response of chloramphenicol (CAP) is observed by the transformation from α-FeOOH to γ-Fe2O3, and from α-FeOOH to α-Fe2O3 nanorods. We found that the oxygen vacancies formed in phase transformation from α-FeOOH to α-Fe2O3 is a key factor in promoting the electrochemical reduction of chloramphenicol. The α-Fe2O3 nanorods-based electrochemical sensors showed a linear response in the CAP concentration range from 0.1 to 75 μM with a limit of detection of 60 nM and an electrochemical sensitivity of 2.86 μA μM−1 cm−2. This work further provides valuable physical insight into the phase-dependent electron transfer kinetics and electrocatalytic activity of metal oxide nanostructures for the rational design of sensing interface.

A highly sensitive electrochemical sensor for the detection of chloramphenicol based on Ni/Co bimetallic metal-organic frameworks/reduced graphene oxide composites

A highly and simply sensitive electrochemical sensor has been developed for the detection of trace chloramphenicol (CAP) in water based on Ni/Co bimetallic metal–organic frameworks-reduced graphene oxide composites [rGO/NiCo-BTC MOFs (BTC = 1,3,5-benzenetricarboxylicacid)] modified glassy carbon electrode (GCE/rGO/NiCo-BTC MOFs). The bare glassy carbon electrode was initially coated with graphene oxide (GO). Subsequently, the GO was electrochemically reduced to obtain reduced graphene oxide (rGO). NiCo-BTC MOFs was grown on the surface of rGO modified electrode by in-situ electrochemical synthesis method to construct GCE/rGO/NiCo-BTC MOFs. The as-made composites films have been characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Further, different electrochemical techniques were utilized for investigating the electrochemical reduction behaviors of CAP at GCE/rGO/NiCo-BTC MOFs. This composites film modified electrode combines the large surface area and excellent electrical properties of rGO with the good catalytic activity of NiCo-BTC MOFs, resulting in a significant enhancement of the electrochemical signal during the electroreduction of CAP. Under the optimized experimental conditions, the sensor exhibits excellent sensing performance for CAP, with a wider linear dynamic range (0.1 − 100 μM), a lower limit of detection (0.235 μM) (S/N = 3) and a ultra-high sensitivity (33.12 μA·μM−1·cm−2). The tap water spiked with different concentrations of CAP were considered. The recoveries range from 97.79 % to 100.07 %, with relative standard deviations ranging from 3.45 % to 5.40 %. The method has been successfully applied for the determination of CAP in real samples, yielding satisfactory results. With further research and development, electrochemical in-situ synthesis of MOFs composites have the potential to revolutionize the design and performance of electrochemical sensors, holding great promise in the field of electrochemical sensing.

A Novel Electrochemical Sensor for Chloramphenicol Based on MXenes and Carbon Nanofiber from Bacterial Cellulose

In this study, three-dimensional porous MXene/carbon nanofiber (CNF) nanocomposites were prepared by assembling environmentally friendly and inexpensive bacterial cellulose (BC) gel sheets as a carbon source with novel two-dimensional MXenes nanoplate clusters and pyrolyzing the composite. The structure, morphology, and electrochemical properties of MXene/CNF was characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. The experimental results revealed that the MXene/CNF nanocomposites had excellent electrical conductivity, large specific surface area, abundant active sites, and excellent electrochemical properties. The sensitive electrochemical determination of chloramphenicol (CAP) was achieved by constructing an electrochemical sensor using the MXene/CNF composite. The response current values of the MXene/CNF sensor exhibited a good linear response with CAP concentration ranging from 0.03-25μM, with a low detection limit of 9 nM. In addition, the sensor demonstrated good repeatability and reproducibility with relative standard deviations of 2.94 and 3.29%, respectively. Remarkably, the developed sensor was successfully used for the real-time detection of CAP in milk and jasmine tea beverage and satisfactory rates were obtained.

The effect of antibiotics contained in milk on the quality and safety of dairy products

During storage, the organic substances of milk undergo a number of complex changes in composition and properties, and new chemical compounds are also formed that radically change the nutritional value, normal appearance, taste and smell of the product under the influence of a number of factors. factors. Regulation of biochemical and microbiological processes during storage and processing of milk is a current trend in the dairy industry. The purpose of the experiment is to determine the effect of antibiotics on the chemical composition, microbiological parameters and organoleptic properties of raw milk and fermented milk products. During the research, it was found that with increasing concentration of penicillin, the consistency of yogurt becomes liquid and heterogeneous, with an off taste and odor. The number of lactic acid bacteria was 3.1 × 104 CFU/ml with the maximum amount of antibiotics in the product (0.1 mg/kg) and 3.4 × 108 CFU/ml without it. Statistically significant differences in the organoleptic properties of yogurt were obtained at the highest concentration of chloramphenicol (0.1 mg/kg). In the remaining samples studied, antibiotic concentrations did not affect the consistency, taste and smell of the product.

Sub-MIC Antibiotics Modulate Productions of Outer Membrane Vesicles in Tigecycline-Resistant Escherichia coli.

Antimicrobial resistance (AMR) has been recognized as one of the most important crises affecting global human health in the 21st century. Tigecycline is one of the last resort antibiotics for treating severe infections caused by multi-drug resistant Enterobacteriaceae. However, the mobile resistance gene tet(X4), which could mediate high-level tigecycline resistance, was discovered in 2019. The outer membrane vesicle (OMV) has been recognized as a new route for horizontal gene transfer; antimicrobial resistant bacteria also have the ability to secret OMVs, while little is known about the impact of antibiotics on the secretion and characteristics of OMVs from tigecycline resistant bacteria till now. This study aimed to investigate the effects of antibiotics on the production and traits of a tigecycline resistant Escherichia coli strain of 47EC. The results showed that sub-inhibitory (1/2 MIC or 1/4 MIC) concentrations of gentamicin, meropenem, ceftazidime, chloramphenicol, tigecycline, ciprofloxacin, polymycin, rifaximin and mitomycin C could significantly increase the secretion of OMVs (0.713 ± 0.05~6.333 ± 0.15 mg/mL) from E. coli 47EC compared to the respective untreated control (0.709 ± 0.03 mg/mL). In addition, the particle sizes of OMVs were generally larger, and the zeta potential were lower in the antibiotics-treated groups than those of the antibiotic-free group. The copy numbers of the tigecycline resistance gene of tet(X4) in the OMVs of most antimicrobial-treated groups were higher than that of the control group. Moreover, transcriptome analysis on ciprofloxacin-treated E. coli 47EC indicated that the SOS response and prophage activation might participate in the ciprofloxacin-induced OMV formation. In conclusion, the clinical application of antibiotics in treating bacterial infections, especially multi-drug resistant bacteria, might lead to the increased secretion of bacterial OMVs and the enrichment of antimicrobial-resistant genes in the OMVs.

Revealing the biological significance of multiple metabolic pathways of chloramphenicol by Sphingobium sp. WTD-1

Chloramphenicol (CAP) is an antibiotic that commonly pollutes the environment, and microorganisms primarily drive its degradation and transformation. Although several pathways for CAP degradation have been documented in different bacteria, multiple metabolic pathways in the same strain and their potential biological significance have not been revealed. In this study, Sphingobium WTD-1, which was isolated from activated sludge, can completely degrade 100 mg/L CAP within 60 h as the sole energy source. UPLC-HRMS and HPLC analyses showed that three different pathways, including acetylation, hydroxyl oxidation, and oxidation (C1-C2 bond cleavage), are responsible for the metabolism of CAP. Importantly, acetylation and C3 hydroxyl oxidation reduced the cytotoxicity of the substrate to strain WTD-1, and the C1-C2 bond fracture of CAP generated the metabolite p-nitrobenzoic acid (PNBA) to provide energy for its growth. This indicated that the synergistic action of three metabolic pathways caused WTD-1 to be adaptable and able to degrade high concentrations of CAP in the environment. This study deepens our understanding of the microbial degradation pathway of CAP and highlights the biological significance of the synergistic metabolism of antibiotic pollutants by multiple pathways in the same strain.

A reagent-based label free electrochemiluminescence biosensor for ultrasensitive quantification of low-abundant chloramphenicol

Today, great attentions have been attracted on chloramphenicol (CAP) to its nonnegligible biotoxicity to human. It is most important and urgent to quantify the low-abundant chloramphenicol by generating simple and efficient analysis approach for the detection of chloramphenicol. Herein, we proposed a novel reagent-based label free electrochemiluminescence (ECL) biosensor based on AuNPs@CoFe-PBA nanomaterials as highly efficient catalysts for luminol/hydrogen peroxide (H2O2) system and target indirectly induced activation of the CRISPR/Cas 12a amplification system for simple and efficient quantification of the low-abundant chloramphenicol. Typically, AuNPs@CoFe-PBA nanomaterials as a novel catalyst for luminol/H2O2 system were enclosed in the X-type DNA hydrogel to greatly inhibit their catalytic performance due to the blocking effect of DNA hydrogel. In presence of target CAP, it induced DNA structure transformation of the aptamer of chloramphenicol to generate a toehold to present catalyzed hairpin assembly (CHA) amplification with the help of two self-designed hairpin structure DNA to perform the hybridizer of the two hairpins, which could activate the CRISPR/Cas 12a system to carry out the DNA cleavage. Its activity breaks the structure of DNA hydrogels and releases AuNPs@CoFe-PBA nanomaterials, which enhances the ECL signals of the luminol/H2O2 systems for simple and sensitive analysis of chloramphenicol. Most importantly, all of the target induced amplifications were performed in the detection solution and the ECL reactions were generated on the bare electrode without any modification to construct a reagent-based label-free analysis system simply with high efficiency for quantification of the low-abundant chloramphenicol. The results showed that there was a good linear relationship between ECL intensity and CAP concentration in range from 10 pg/mL to 1 ug/mL with a detection limit of 7.75 pg/mL, providing great potentials to quantify the low-abundant chloramphenicol and some other biomarkers for early disease diagnosis, food safety testing and environmental analysis.

Quantitative detection of chloramphenicol residue in fish based on SERS aptasensor coupled with magnetic separation

Chloramphenicol (CAP) is a widely used antibiotic in aquaculture. However, its improper use and the resulting residues in fish have become a significant concern for human health. Conventional methods for quantifying CAP are complex and expensive, leading to the need for more efficient and sensitive techniques. In this study, both CAP aptamer and sulfhydryl (SH) complementary DNA strand (SH-cDNA) were bound to gold and silver core–shell nanoparticles (Ag@Au CSNPs) and core–shell magnetic nanoparticles (Fe3O4@Au MNPs) via Au-S covalent bonding and were used as SERS signal probes and capture probes, respectively. The principle of aptamer competitive recognition was applied to achieve the quantitative detection of CAP in fish. The capture probe and the signal probe generated strong signals by complementary hybridization in the absence of CAP in the detection system. In the presence of CAP, the CAP aptamer bonded to the CAP, and the signal probe was separated from the capture probe, resulting in a linear decrease in SERS signal intensity. Consequently, there was a strong inverse relationship between SERS intensity and the logarithm of CAP concentration, ranging from 10-5 to 10-1 µg·mL−1 (R2 = 0.9974). The limit of detection (LOD) was as low as 16 pg·mL−1. The established method exhibited strong selectivity, anti-interference, reproducibility, and stability.

Carbon-dots encapsulated luminescent metal–organic frameworks@surface molecularly imprinted polymer: A facile fluorescent probe for the determination of chloramphenicol

In this study, carbon dots (CDs)-encapsulated luminescent metal–organic frameworks@surface molecularly imprinted polymer (CDs@MOF@SMIP) was facilely prepared and applied as fluorescent probe for specific identification and sensitive detection of chloramphenicol (CAP) in food. Fluorescent CDs, serving as signal tags, were encapsulated within metal–organic backbones (ZIF-8), yielding luminescent MOF materials (CDs@ZIF-8). The synthesized CDs, CDs@ZIF-8 and CDs@ZIF-8@SMIP were investigated by morphological and structural characterizations (UV–Vis, XRD, FT-IR, BET, TEM). The CDs@ZIF-8@SMIP probe was demonstrated to have remarkable selectivity and sensitivity towards CAP. Its fluorescence decreased linearly with CAP concentration from 0.323 μg L-1 (0.001 μM) to 8075.0 μg L-1 (25.0 μM), featuring a low detection limit of 0.08 μg L-1. The CDs@ZIF-8@SMIP-based fluorescence strategy achieved satisfactory recoveries (95.5 % − 101.0 %) in CAP-spiked commercial foods with RSD < 4.4 % (n = 3). These results indicate that this method can effectively detect trace CAP in food matrices and has broad application prospects.

Molecularly imprinted polymers-aptamer electrochemical sensor based on dual recognition strategy for high sensitivity detection of chloramphenicol

In this paper, an electrochemical sensor based on a dual recognition strategy of molecularly imprinted polymers (MIPs) and aptamer (Apt) has been designed for the high sensitivity detection of chloramphenicol (CAP). Here, MIPs and Apt have provided dual recognition sites to greatly improve the specific recognition ability of the sensor. Chitosan-multi-walled carbon nanotubes (CS-MWNTs) and AuNPs (gold nanoparticles) have been used for their excellent electrical conductivity. When CAP existed in the detection environment, the imprinted cavities with specific recognition ability bound to CAP through forces such as hydrogen bonds. It hindered the rate of electron transfer and resulted in a decrease in current value. Quantitative detection of CAP could be achieved after analyzing the relationship between the concentration of CAP and the change of current value. After optimizing the experimental parameters, the detection range of the sensor was 10−8 g/L-10−2 g/L with the limit of detection of 3.3 × 10−9 g/L, indicating that the sensor had a high practical application potential.

Effects of Different Treatments on Seed Germination of Salvia miltiorrhiza

To study the effects of different treatments on the germination characteristics of Salvia miltiorrhiza seed, Salvia miltiorrhiza seeds were treated by fludioxonil and carbendazim, and were studied with different thickness of covering soil. The results showed that with the increase of soil cover thickness, the germination rate of Salvia miltiorrhiza seeds significantly decreased. The thickness of covering soil was 0 cm, the germination of Salvia miltiorrhiza seeds was the best and the germination rate was 42.08%. When the thickness of covering soil was 1.0 cm, the germination rate of Salvia miltiorrhiza seeds significantly decreased, only 2.91%, which was 93.08% lower than the control. The appropriate concentration of seed coating agent can improve the germination rate of Salvia miltiorrhiza seeds. When the soil thickness was 0 cm+1.25 g∙L-1 fludioxonil, the best germination effect of Salvia miltiorrhiza seeds was observed, and the germination rate was 59.17%, which increased 40.61% compared to 0 cm soil alone. The germination rate of Salvia miltiorrhiza seeds treated with 0 cm+2.5 g∙L-1 fludioxonil was only 13.75%, which was 28.33% lower than the germinationg rate with the soil thickness of 0 cm alone. There was no significant difference in the germination rate of Salvia miltiorrhiza seeds treated with 0.05% carbendazim compared with the control group; The germination rate of Salvia miltiorrhiza seeds treated with 0.1% carbendazim was significantly lower than that of the control group covered with 0 cm soil alone. In summary, The best germination level of Salvia miltiorrhiza seed was the cover thickness of 0 cm soil and 1.25 g ∙ L-1 concentration of fludioxonil, ( 0 cm+1.25 g∙L-1). The treatment of seeds with 2.5 g∙L-1 concentration of chloramphenicol showed a significant inhibitory effect on the germination of Salvia miltiorrhiza seeds. In conclusion, Salvia miltiorrhiza seeds treated with 1.25 g∙L-1 concentration of fludioxonil and 0 cm covered soil, the germination rate, germination potential, and germination index are 59.17%, 51.67%, and 14.27, respectively, which increased by 40.61%, 61.07%, 77.28% compared with the soil of 0 cm alone. It is suggested that breeding of Salvia miltiorrhiza seeds should be carried out on land with the appropriate concentration of fludioxonil.

Application of Optimization Models in Modification of Nutrient- Chloramphenicol Agar Medium for Use in Selective Isolation of Pseudomonasfluorescens.

Commercially available medium for selective isolation of Pseudomonas are relatively expensive. Incorporation of chloramphenicol into nutrient agarhas been used in the selective isolation of Pseudomonasfluorescens. Theaim of this study was to apply optimization in modification of nutrient-chloramphenicol agar medium (NCAM) so as to optimize it for selective isolation of Pseudomonas species. Water sample determined to contain fluorescent greenish-pigment producing bacteria (FGPB) was used for the optimization study. Medium component selected for the optimization process were pH, NaCl concentration (NC), and chloramphenicol concentration (CC), with value ranges of 7.0 – 8.2, 0.5 – 1.0 %, and 40 – 60 ?g/ml, respectively. Fifteen media variations were derived from combination of these ranges using Box-Behnken design matrix,and were used in culturing the water sample for isolation of FGPB. Relationship between obtained proportions of bacterial populations that are FGPB and chosen media components were calculated using polynomial equation for three factors design. Prediction profiles derived from the equation showed that the highest proportion of bacterial populations that are FGPB was achievable at pH, NC, and CC combination values of 7.0, 0.2 %, and 60 ?g/ml, respectively. NCAM with this optimized combination increased the efficiency of selectively isolating FGPB from the water samplefrom 0.008 to 0.011 %. Physicochemical/biochemical testing showed that the FGPBisolates were Pseudomonas fluorescens. It is concluded that NCAM with pH 7.0, NaCl concentration of 0.2 %, and chloramphenicol concentration of 60 ?g/ml can be used for selective isolation of Pseudomonas fluorescens with optimum efficiency.

Quercetin capped silver nanoparticles as an electrochemical sensor for ultrasensitive detection of chloramphenicol in food and water samples

This study demonstrates the green, rapid and simple synthesis of silver nanoparticles (AgNPs) by employing bio-flavonoid (quercetin), which acts as a stabilizing and reducing agent. The nanoparticles were prepared by a simple one pot method. AgNPs were characterized by using various characterization techniques like High-resolution transmission electron microscopy (HRTEM), Ultraviolet-visible spectroscopy (UV-visible), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Field emission scanning electron microscopy (FESEM) with energy dispersive spectrometry (EDS). Later on, these nanoparticles were further used to construct the electrochemical sensing electrode and also for the precise and sensitive determination of chloramphenicol (CAP) antibiotic using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The fabricated sensor exhibits outstanding electrochemical performance, with a linear response for CAP concentrations between 0 μM to 80 μM and a limit of detection (LOD) of 265.6 nM. Further, the present sensor displayed impressive selectivity, reproducibility and high sensitivity. The designed sensor was deployed for the detection of CAP in real samples (water, milk and honey) to demonstrate its ability to perform real-time analysis with a satisfactory recovery rate. The results of real sample analysis using LSV were compared with the standard method (HPLC) and found comparable. Hence, the developed electrochemical sensor displayed great potential for detecting CAP in real samples with desirable recovery rates.

Competitive immunoassay using enzyme-regulated Fe3O4@COF/Fe3+ fluorescence probe for natural chloramphenicol detection

Accurate and sensitive detection of chloramphenicol (CAP) in natural samples is essential for ensuring human health. Herein, an enzyme-regulated fluorescence sensor using Fe3O4@COF/Fe3+ probe, is developed for CAP determination. Fe3O4@COF, synthesized via hydrothermal method, exhibits dual functions as a magnetic carrier and signal probe. Bovine serum albumin conjugated-chloramphenicol, adsorbed on the surface of Fe3O4@COF, competes with CAP for antibody binding. The antibody interacts with alkaline phosphatase via the biotin-streptavidin system. Meanwhile, ascorbic acid, produced from the enzyme-catalyzed reaction dominated by alkaline phosphatase, effectively restores the fluorescence of Fe3O4@COF that is quenched by Fe3+. After experimental verification and gradual optimization, a logarithmic linear relationship between CAP concentration and fluorescence intensity is established in the range of 2 × 10−4∼10 μg mL−1, with a good limit of detection (9.2 × 10−5 μg mL−1). Proposed method exhibits excellent stability (15 days) and reusability (8 cycles), providing a sensitive and reliable method for accurate CAP detection. The readouts show good agreement with HPLC and recoveries during laboratory and natural CAP analysis.

An Advanced Molecularly Imprinted Photochemical Sensor Based Carbon Quantum dots for Highly Sensitive Detection of Chloramphenicol in Food.

A facile method which combines the advantages of carbon quantum dots and molecular imprinting technology to design a fluorescence molecular imprinting sensor for the high sensitivity and selective detection of chloramphenicol. The fluorescent molecule imprinted polymers are synthesized by sol-gel polymerization using carbon quantum dots as functional monomers and fluorescent sources, TEOS as crosslinkers, breaking with the traditional understanding of an additional functional monomer. Under optimal experimental, as the concentration of chloramphenicol increases, the fluorescence intensity of the fluorescence molecule imprinting sensor gradually decreases. The concentration of chloramphenicol is linear in the range of 5-100µg/L and the detection limit is 1µg/L (N/S = 3). The sensor is able to detect chloramphenicol in milk, enabling the application of real samples. The results show that this work provides an easy method to preparing fluorescent molecular imprinting sensors for the detection of chloramphenicol in milk.

Efficient Electrochemical Oxidation of Chloramphenicol by Novel Reduced TiO2 Nanotube Array Anodes: Kinetics, Reaction Parameters, Degradation Pathway and Biotoxicity Forecast.

The key component of electrochemical advanced oxidation technology are high-efficiency anodes, and highly efficient and simple-to-prepare materials have generated a lot of interest. In this study, novel self-supported Ti3+-doped titanium dioxide nanotube arrays (R-TNTs) anodes were successfully prepared by a two-step anodic oxidation and straightforward electrochemical reduction technique. The electrochemical reduction self-doping treatment produced more Ti3+ sites with stronger absorption in the UV-vis region, a band gap reduction from 2.86 to 2.48 ev, and a significant increase in electron transport rate. The electrochemical degradation effect of R-TNTs electrode on chloramphenicol (CAP) simulated wastewater was investigated. At pH = 5, current density of 8 mA cm-2, electrolyte concentration of 0.1 M sodium sulfate (Na2SO4), initial CAP concentration of 10 mg L-1, CAP degradation efficiency exceeded 95% after 40 min. In addition, molecular probe experiments and electron paramagnetic resonance (EPR) tests revealed that the active species were mainly •OH and SO4-, among which •OH played a major role. The CAP degradation intermediates were discovered using high-performance liquid chromatography-mass spectrometry (HPLC-MS), and three possible degradation mechanisms were postulated. In cycling experiments, the R-TNTs anode demonstrated good stability. The R-TNTs prepared in this paper were an anode electrocatalytic material with high catalytic activity and stability, which could provide a new approach for the preparation of electrochemical anode materials for difficult-to-degrade organic compounds.

Development of Bioluminescent Virulent Aeromonas hydrophila for Understanding Pathogenicity.

Virulent Aeromonas hydrophila (vAh) strains that cause motile Aeromonas septicemia (MAS) in farmed channel catfish (Ictalurus punctatus) have been an important problem for more than a decade. However, the routes of infection of vAh in catfish are not well understood. Therefore, it is critical to study the pathogenicity of vAh in catfish. To this goal, a new bioluminescence expression plasmid (pAKgfplux3) with the chloramphenicol acetyltransferase (cat) gene was constructed and mobilized into vAh strain ML09-119, yielding bioluminescent vAh (BvAh). After determining optimal chloramphenicol concentration, plasmid stability, bacteria number-bioluminescence relationship, and growth kinetics, the catfish were challenged with BvAh, and bioluminescent imaging (BLI) was conducted. Results showed that 5 to 10 µg/mL chloramphenicol was suitable for stable bioluminescence expression in vAh, with some growth reduction. In the absence of chloramphenicol, vAh could not maintain pAKgfplux3 stably, with the half-life being 16 h. Intraperitoneal injection, immersion, and modified immersion (adipose fin clipping) challenges of catfish with BvAh and BLI showed that MAS progressed faster in the injection group, followed by the modified immersion and immersion groups. BvAh was detected around the anterior mouth, barbels, fin bases, fin epithelia, injured skin areas, and gills after experimental challenges. BLI revealed that skin breaks and gills are potential attachment and entry portals for vAh. Once vAh breaches the skin or epithelial surfaces, it can cause a systemic infection rapidly, spreading to all internal organs. To our best knowledge, this is the first study that reports the development of a bioluminescent vAh and provides visual evidence for catfish-vAh interactions. Findings are expected to provide a better understanding of vAh pathogenicity in catfish.

Simultaneous Dual-Sensing Platform Based on Aptamer-Functionalized DNA Hydrogels for Visual and Fluorescence Detection of Chloramphenicol and Aflatoxin M1.

In this study, a chloramphenicol and aflatoxin M1 aptamer-functionalized DNA hydrogel was designed for the simultaneous detection of chloramphenicol and aflatoxin M1 for the first time. The acrydite-modified chloramphenicol aptamer sequence was used to synthesize the DNA hydrogel and for visual detection of chloramphenicol depending on the gel-to-sol transition of the target-responsive DNA hydrogel. The DNA hydrogel formulation was set as follows: 60% of each linear polyacrylamide-DNA conjugate and 40% of acrylamide and chloramphenicol aptamer/DNA strand-1 at a molar ratio of 1:1, and the lowest concentration of chloramphenicol leading to gel dissociation was 1.0 nM at 25 °C. Furthermore, the formalized aptamer-functionalized DNA hydrogel was used to detect aflatoxin M1 by measuring the recovery of the fluorescence signal that was quenched when the FAM-labeled aflatoxin M1 aptamer and BHQ1-labeled DNA strand-2 were hybridized to form a double-stranded DNA in the network of hydrogel. The detection platform was successfully applied to the detection of chloramphenicol and aflatoxin M1, both in aqueous solution and in milk. The aptamer-functionalized DNA hydrogel had detection (LOD) and quantification limits (LOQ) for aflatoxin M1 as 1.7 and 5.2 nM, respectively. Using two aptamer sequences with high affinity and specificity, the dual-sensing platform based on the DNA hydrogel achieved higher selectivity for chloramphenicol and aflatoxin M1, which demonstrated its potential as a reliable simultaneous detection platform against two different targets for monitoring food safety.