Oxalated zero valent iron enables highly efficient heterogeneous Fenton reaction by self-adapting pH and accelerating proton cycle

Heterogeneous Fenton reactions of zero-valent iron (ZVI) requires the sufficient release of Fe(II) to catalyze the H₂O₂ decomposition. However, the rate-limiting step of proton transfer through the passivation layer of ZVI restricted the Fe(II) release via Fe⁰ core corrosion. Herein we modified the shell of ZVI with highly proton-conductive FeC₂O₄·2H₂O by ball-milling (OA-ZVI^bm), and demonstrated its high heterogeneous Fenton performance of thiamphenicol (TAP) removal, with 500 times enhancement of the rate constant. More importantly, the OA-ZVI^bm/H₂O₂ showed little attenuation of the Fenton activity during 13 successive cycles, and was applicable across a wide pH range of 3.5-9.5. Interestingly, the OA-ZVI^bm/H₂O₂ reaction showed pH self-adapting ability, which initially reduced and then sustained the solution pH in the range of 3.5-5.2. The abundant intrinsic surface Fe(II) of OA-ZVI^bm (45.54% vs. 27.52% in ZVI^bm, according to Fe 2p XPS profiles) was oxidized by H₂O₂ and hydrolyzed to generate protons, and the FeC₂O₄·2H₂O shell favored the fast transfer of protons to inner Fe⁰, therefore, the consumption-regeneration cycle of protons were accelerated to drove the production of Fe(II) for Fenton reactions, demonstrated by the more prominent H₂ evolution and nearly 100% H₂O₂ decomposition by OA-ZVI^bm. Furthermore, the FeC₂O₄·2H₂O shell was stable and slightly decreased from 1.9% to 1.7% after the Fenton reaction. This study clarified the significance of proton transfer on the reactivity of ZVI, and provided an efficient strategy to achieve the highly efficient and robust heterogeneous Fenton reaction of ZVI for pollution control.

Effects of natural nanoparticles on the acute toxicity, chronic effect, and oxidative stress response of phenicol antibiotics in Daphnia magna

Natural nanoparticles (NNP) are ubiquitous in natural water and can interact with other contaminants, causing ecotoxic effects on aquatic nontarget organisms. However, the impact of NNPs on the ecotoxicity of antibiotics remains largely unknown. This work investigated the acute toxicity, chronic effect, and oxidative response and damage in Daphnia magna co-exposed to phenicol antibiotics (chloramphenicol, thiamphenicol) and different concentrations of NNPs (10 mg/L: environmentally relevant concentration; 100 mg/L: a high concentration that caused no apparent immobilization in D. magna). The results showed that the acute toxicity of chloramphenicol was increased by 10 mg/L NNPs but decreased by 100 mg/L NNPs; both concentrations of NNPs increased and decreased acute toxicities of thiamphenicol and chloramphenicol + thiamphenicol treatments, respectively. After long-term exposure, phenicol antibiotics (1 μg/L) and NNP (10 mg/L) mixtures in environmentally relevant concentrations significantly affected the reproduction of D. magna but did not influence their growth. The catalase activity, reduced glutathione level, and malonaldehyde content in D. magna also varied with the NNPs concentrations. Notably, the lowest concentration of thiamphenicol and chloramphenicol + thiamphenicol combined with NNPs significantly increased the malondialdehyde content in D. magna compared with the control, indicating membrane lipid peroxidation occurred in daphnids. This study suggests that the toxic effects of contaminants and NNPs on aquatic organisms should be considered thoroughly to avoid underestimating the hazard of these pollutants in the actual aquatic environment.

Down/up-conversion dual-mode ratiometric fluorescence imprinted sensor embedded with metal-organic frameworks for dual-channel multi-emission multiplexed visual detection of thiamphenicol

The establishment of a fluorescence sensing system for sensitive and selective visual detection of trace antibiotics is of great significance to food safety and human health risk assessment. A simple and rapid one-pot strategy was developed successfully to synthesize a down/up-conversion dual-excitation multi-emission fluorescence imprinted sensor for dual-channel thiamphenicol (TAP) detection. In this strategy, the metal-organic frameworks were in situ incorporated into the fluorescence imprinted sensor, guiding the coordination induced emission of abiotic carbon dots and signal-amplification effect of fluorescence sensing. Under dual-excitation (370 nm and 780 nm), the fluorescence imprinted sensor exhibited a dual-channel fluorescence response toward TAP with two-part linear ranges of 5.0 nM-6.0 μM and 6.0 μM-26.0 μM. Significantly, the fluorescence color ranged from blue to purple to red can be observed with the naked eye. The results of the dual-channel TAP determination in actual samples by the fluorescence imprinted sensor indicated that the fluorescence imprinted sensor provided a sensitive, selective, and multiplexed visual detection of TAP in complex sample.

Effect of Carbonyl Cyanide Chlorophenylhydrazone on Intrabacterial Concentration and Antimicrobial Activity of Amphenicols against Swine Resistant Actinobacillus pleuropneumoniae and Pasteurella multocida

Effects and mechanism of carbonyl cyanide chlorophenylhydrazone (CCCP) on antimicrobial activity of florfenicol (FF) and thiamphenicol (TAP) were investigated against amphenicol-resistant Actinobacillus pleuropneumoniae and Pasteurella multocida isolated from diseased swine. Broth microdilution and time-kill assays indicated that CCCP dose-dependently and substantially (4-32 fold MIC reduction) improved amphenicol antimicrobial activity. When combined with CCCP at the lowest literature reported dose (2-5 μg/mL), 85% FF resistant A. pleuropneumoniae and 92% resistant P. multocida showed significantly reduced FF MICs (≥ 4-fold). In contrast, none or few of the susceptible A. pleuropneumoniae and P. multocida had FF MICs reduction ≥ 4-fold. 90% FF resistant A. pleuropneumoniae and 96% resistant P. multocida carried the floR gene, indicating strong association with the FloR efflux pump. With CCCP, the intracellular FF concentration increased by 71% in floR+ resistant A. pleuropneumoniae and 156% in floR+ resistant P. multocida strains but not the susceptible strains. The degree of reduction in TAP MICs was found consistently in parallel to FF for both bacteria. Taken together, partially attributed to blockage of drug-efflux, the combination of FF or TAP with CCCP at sub-cytotoxic concentrations was demonstrated and showed feasibility to combat amphenicol-resistant A. pleuropneumoniae and P. multocida isolated from diseased swine.

New insights into thiamphenicol biodegradation mechanism by Sphingomonas sp. CL5.1 deciphered through metabolic and proteomic analysis

Biological treatment is an efficient and economical process to remove thiamphenicol (TAP) residues from the environment. The discovery of TAP-degrading bacteria and the decryption of its biodegradation mechanism will be beneficial to enhance the biological removal of TAP. In this study, Sphingomonas sp. CL5.1 was found to be capable of catabolizing TAP as the sole carbon, nitrogen, and energy source. This strain could degrade 93.9% of 25 mg/L TAP in 36 h, and remove about 11.9% of the total organic carbon of TAP. A novel metabolism pathway of TAP was constructed, and the enzymes involved in TAP metabolism in strain CL5.1 were predicted via proteomic and metabolic analysis. TAP was proposed to be transformed to O-TAP via oxidation of C₃-OH and DD-TAP via dehydration of C₃-OH and dehydrogenation of C₁-OH. A novel glucose-methanol-choline (GMC) family oxidoreductase CapO was predicted to be involved in the oxidation of C₃-OH. O-TAP was supposed to be further cleaved into DCA, glycine, and PMB. Glycine might be a pivotal direct nitrogen source for strain CL5.1, and it could be involved in nitrogen metabolism through the glycine cleavage system or directly participate in the biosynthetic processes.

Single and ternary competitive adsorption-desorption and degradation of amphenicol antibiotics in three agricultural soils

The widespread usage of veterinary antibiotics results in antibiotic contamination and increases environmental risks. This study was evaluated the single and ternary competitive adsorption-desorption and degradation of three amphenicol antibiotics (AMs): chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) in three agricultural soils. The adsorption capacity of amphenicol antibiotics in the soil was weak, and the K_f value was in the range of 0.15-3.59 μg^1-1/nL^1/n kg^-1. In the single adsorption-desorption experiment, the ranked order of adsorption capacity was TAP > FF > CAP. However, in the ternary competitive adsorption experiment, the order was changed to be CAP > FF > TAP. The degradation of AMs in soils was performed at various conditions. All AMs were vulnerable to microbial degradation in soils. A higher initial concentration would reduce the degradation rate and enhance the persistence of AMs in soil. The degradation of AMs was positively influenced by changes in soil moisture content and culture temperatures up to 30 °C and decreased at higher temperatures. An equation was used to predict the leachability of AMs in soils and assess their risk to the water environment. The weak adsorption capacity and poor persistence of FF indicated that it may have a strong effect on groundwater based on the equation. It is imperative to further assess the biological impacts of FF at environmentally relevant concentrations given its mobility and extensive use in the livestock industry.

Evaluation of the Acute Effects and Oxidative Stress Responses of Phenicol Antibiotics and Suspended Particles in Daphnia magna

Suspended particles (SP) exist widely in various water systems and are able to adsorb other pollutants in water, producing ecotoxic effects on aquatic nontarget species. Until now, however, few studies have focused on the effects of SP on antibiotics. Therefore, the present study investigated the effects of the mixtures of SP and phenicol antibiotics (chloramphenicol [CAP], thiamphenicol [TAP]) on acute toxicity and oxidative stress responses in Daphnia magna. The results indicated that the acute toxicity of phenicol antibiotics in D. magna was increased when combined with SP. Besides, the immobilization of daphnids caused by phenicol drugs in the presence of 10 mg/L of SP was more intense than that with 200 mg/L of SP. Furthermore, the impact of SP with diverse concentrations on the activity of catalase and the level of reduced glutathione in D. magna was different. Notably, almost all CAP + TAP + SP treatments markedly increased malondialdehyde content in D. magna, causing potential cellular oxidative damage in D. magna. In summary, the present study provides insights into the toxic effects of phenicol antibiotic and SP mixtures on aquatic organisms. Environ Toxicol Chem 2021;40:2463-2473. © 2021 SETAC.

Efficient removal of antibiotic thiamphenicol by pulsed discharge plasma coupled with complex catalysis using graphene-WO3-Fe3O4 nanocomposites

Pulsed discharge plasma (PDP) induced complex catalysis for synergetic removal of thiamphenicol (TAP) was investigated using graphene-WO₃-Fe₃O₄ nanocomposites. The prepared samples were characterized systematically in view of the structure and morphology, chemical bonding state, optical property, electrochemical property and magnetic property. Based on characterization and TAP degradation, the catalytic performance followed: graphene-WO₃-Fe₃O₄>graphene-WO₃>WO₃, and the highest removal efficiency and kinetic constant could reached 99.3% and 0.070 min^-1, respectively. With increase of catalyst dosage, the removal efficiency firstly enhanced and then declined. Lower pH value was beneficial for TAP degradation. The prepared graphene-WO₃-Fe₃O₄ owed higher stability and lower dissolution rate of iron ion. The rGO-WO₃-Fe₃O₄ could decompose O₃ and H₂O₂ into more ·OH in PDP system. The degradation intermediates were characterized by fluorescence spectrograph, LC-MS and IC. Based on the detected intermediates and discrete Fourier transform (DFT) analysis, degradation pathway of TAP was proposed. Besides, the toxicity of intermediates was predicted. Finally, catalytic degradation mechanism of TAP by PDP with graphene-WO₃-Fe₃O₄ was summarized.

Improved antibacterial efficiency of inhaled thiamphenicol dry powders: Mathematical modelling of in vitro dissolution kinetic and in vitro antibacterial efficacy

Thiamphenicol (TAP) is reported to be effective against many respiratory pathogens including methicillin-resistant Staphylococcus aureus (MRSA). However, its poor solubility in water remains as one of the obstacles hindering the preparation of inhalable TAP formulations. The aim of this study was to improve the dissolution rate of TAP by micronization, and investigate whether variations in the dissolution rates of TAP would affect its in vitro antibacterial activity. Inhalable dry powders composed of TAP microcrystals (MDP) or nanocrystals (NDP) were prepared by using a wet ball milling method followed by spray drying. The morphology, solid state and in vitro dissolution of these dry powders were characterized. In vitro antibacterial activities of the inhalable TAP dry powders against a MRSA strain were evaluated. A dissolution-efficacy model relating antibacterial activity with time and dissolution rate was established via modified time-kill assays. Upon being spray dried, the volumetric mean diameters of MDP and NDP were found to be around 5 µm. Solid state analyses showed that MDP and NDP possess the same crystalline form as the raw materials. NDP exhibited faster in vitro dissolution rate as compared to MDP. The in vitro antibacterial efficiency of NDP and MDP were superior to raw TAP when the test was performed at a TAP concentration of 32 mg/L. Simulated colony forming units predictions were consistent with the result measured in the time-kill experiments with Raw TAP, MDP and NDP. This study characterized the effect of the dissolution rate of TAP dry powders on in vitro antibacterial activity against MRSA, and an enhanced antibacterial activity of TAP was observed with an increase in the dissolution rate of TAP from the dry powders at certain concentration ranges.

Biodegradation and metabolic fate of thiamphenicol via Chlorella sp. UTEX1602 and L38

Thiamphenicol (TAP) is a typical medicament in animal husbandry and aquaculture for treating diverse infections. In this work, thiamphenicol biodegradation performance via microalgae was tested. The cultivation results showed that TAP could be biodegraded via the target algae. Chlorella sp. L38 presented strong adaptive ability to high concentration TAP. Biodegradation, biosorption and bioaccumulation were the dominant metabolic fates. Biodegradation contributed around 97% of the total removal efficiency at the TAP concentration of 46.2 mg·L^-1. The removal of TAP by Chlorella L38 and UTEX1602 agreed with the kinetic range of zero-order reaction, and the shortest half-lives were 3.2 d and 5.0 d. Based on the identification of metabolites, the metabolic pathway of TAP by microalgae was proposed, including chlorination, chlorine substitution, dehydration and hydroxylation. Therefore, biological treatment via microalgae has the potential for TAP purification.

A simple and rapid LC-MS/MS method for the determination of amphenicols in Nile tilapia

A quantitative method for analysis of amphenicols (chloramphenicol - CAP, thiamphenicol - TAP and florfenicol - FF) in Nile tilapia using LC-MS/MS is described. A simple sample preparation procedure was optimized using a Plackett-Burman design. The method was validated in accordance with Decision 2002/657/EC. Repeatability and reproducibility were less than 10.7% and 16%, respectively, for all compounds. Recoveries varied from 79.8% to 92.0%. CCα was 0.019, 54.81 and 54.93 μg.kg^-1 for CAP, FF and TAP, respectively. CCβ was 0.068, 64.88 and 58.91 μg.kg^-1 for CAP, FF and TAP, respectively. Limits of quantification (LOQ) were 12.5 μg.kg^-1 for FF and TAP and 0.15 μg.kg^-1 for CAP. Nile tilapia fillets (n = 32) analyzed did not contain chloramphenicol. Thiamphenicol was detected in one sample (3.1%) and florfenicol was detected in every sample, all of them at concentrations below the maximum residue limit.

Electrocatalytic reduction of low-concentration thiamphenicol and florfenicol in wastewater with multi-walled carbon nanotubes modified electrode

The electrocatalytic reduction of thiamphenicol (TAP) and florfenicol (FF) was investigated with multi-walled carbon nanotubes (MWCNTs) modified electrode. MWCNTs was dispersed in pure water with the assistance of dihexadecyl phosphate (DHP), and then modified on glassy carbon electrode (GCE). The electrocatalytic reduction conditions, such as bias voltage, supporting electrolyte and its initial pH, and the initial concentrations of TAP and FF, were also optimized. The experimental results indicated that the removal efficiencies of 2mgL^-1 TAP and FF in 0.1M NH₃·H₂O-NH₄Cl solution (pH 7.0) reached 87% and 89% at a bias voltage of -1.2V after 24h electrocatalytic reduction, respectively. The removal process could be described by pseudo first-order kinetic model, and the removal rate constants of TAP and FF were obtained as 0.0837 and 0.0915h^-1, respectively. The electrocatalytic reduction products of TAP and FF were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the possible reduction mechanisms were preliminarily analyzed. Electrocatalytic reduction is promising to remove low-concentration TAP and FF in wastewater with the MWCNTs modified electrode, and may cut down their toxicity through dehalogenation and carbonyl reduction.

[New drugs for horses and production animals in 2015]

In 2015, four newly developed active pharmaceutical ingredients for horses and food-producing animals were released on the German market for veterinary drug products. These were the bisphosphonate Clodronic Acid (Osphos®), the 5-hydroxytryptamine (2A) receptor antagonist Ketanserin (Vulketan®), the aminoglycoside antibiotic Paromomycin (Parofor®) and the antibiotic Thiamphenicol (TAF Spray®) from the fenicole group. With Chlorphenamine, a temporary not available active ingredient was reapproved in a new drug. Furthermore, three veterinary drugs with a new formulation as well as one product with a new strength and two products with a new combination of active pharmaceutical ingredients have been launched.

Development of a subcritical water extraction approach for trace analysis of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in poultry tissues

Subcritical water extraction was investigated as a novel and alternative technology for the separation of trace amounts of chloramphenicol, thiamphenicol, florfenicol and its major metabolite florfenicol amine from poultry tissues and its results were compared with those of conventional shaking extraction, ultrasonic extraction, and pressurized liquid extraction. Decreasing the polarity of water by successively increasing the extraction temperature from 50°C to 200°C at the moderate pressure enabled selective, highly effective extractions to be performed. Rapid quantification of the target compounds was carried out by ultra-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). The critical parameters of subcritical water extraction such as solvent modifier, temperature, pressure, extraction time, and static cycles were varied with control. The optimized extraction procedures using subcritical water as extraction solvent, were carried out on a pressurized liquid extractor operated at 150°C and 100bar, applying two static cycles for 3min. Average recoveries of the four analytes from fortified samples ranged between 86.8% and 101.5%, with relative standard deviations (RSDs) lower than 7.7%. The limits of detection (LODs) and quantification (LOQs) for the target compounds were in the ranges of 0.03-0.5μgkg(-1) and 0.1-2.0μgkg(-1), respectively. The proposed method is fast, sensitive, water-based thus more environmental acceptable, making it a suitable replacement for conventional organic solvent extraction in veterinary drug residue analysis.

UPLC-MS/MS determination of thiamphenicol in human plasma and its application to a pharmacokinetic study

A sensitive and rapid ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to determine thiamphenicol (TAP) in human plasma using chlorzoxazone as the internal standard (IS). Sample preparation was accomplished through a liquid-liquid extraction procedure with ethyl acetate to precipitation of plasma protein, and to a 0.1 mL plasma sample. The analyte and IS were separated on an Acquity UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) with the mobile phase of acetonitrile and 1% formic acid in water with gradient elution at a flow rate of 0.40 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization (ESI) by multiple reactions monitoring (MRM) of the transitions at m/z 354.3→185.1 for TAP and m/z 168.1→132.1 for IS. The linearity of this method was found to be within the concentration range of 10-8000 ng/mL with a lower limit of quantification of 10 ng/mL. Only 1.5 min was needed for an analytical run. The method herein described was superior to previous methods and was successfully applied to the pharmacokinetic study of TAP in healthy Chinese volunteers after oral administration.