Chlortetracycline Research Articles

Introducing direct probe electrospray ionization tandem mass spectrometry in apiculture: Comparison with other mass spectrometric methods for the determination of antibiotics in bees and honey

Amphenicols and tetracyclines (TCs) antibiotics use in apiculture is mainly focused on the treatment of bee brood diseases. Despite their efficiency, the serious genotoxic effects that some elicit led to their banning for use in apiculture and for chloramphenicol (CAP) in all food-producing animals. In this work, three tandem mass spectrometric methods were developed and validated for the analysis and quantification of CAP, thiamphenicol (TF), florfenicol (FF), tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) in honey and honeybees. With the first, we have demonstrated the first use of probe electrospray ionization (PESI) in conjunction with tandem mass spectrometry (MS/MS) for antibiotics determination in honey and bees entailing a minimum sample preparation for bees, resulting in rapid chemical analysis for both commodities. The second was a reversed-phase HPLC-ESI-MS/MS method sharing the same scope. With the third chiral HPLC-ESI-MS/MS method, it was attempted to separate CAP stereoisomers in both commodities since reports have shown that only the D-threo isomer displays antimicrobial properties. The analytical methods fulfilled validation criteria demonstrating recoveries in the range of 74–92%, managing to address the minimum required performance limit (MRPL) for CAP, with the exception of PESI-MS/MS. The latter displayed a detection capability (CCβ) for all compounds in proximity to 1 ng/g, and an overall runtime of 1.5 min. In total, 68 samples of honeybees and honey were evaluated for amphenicols and TCs residues. CAP was detected only in two honeybee samples, while one honey sample was positive to TC and OTC was detected in traces in another sample. PESI-MS/MS managed to quantify both TC in honey and CAP in bees in proximity to the values assigned by the conventional HPLC-ESI-MS/MS methods. With regard to the separation of CAP's isomers, the chiral method managed to resolute all isomers and quantify CAP in one bee sample in the form of its L-threo stereoisomer. Overall, ABCs detection in honey and related matrices still constitutes a challenge, considering their prevalence and potential applications in major honey-producing countries.

Molecular dynamics simulations on interactions of five antibiotics with luciferase of Vibrio Qinghaiensis sp.-Q67

A large number of antibiotics have been used in the medical industry, agriculture, and animal husbandry industry in recent years. It may cause pollution to the aquatic environment and ultimately threaten to human health due to their prolonged exposure to the environment. We aim to study the toxicity mechanism of enrofloxacin (ENR), chlortetracycline hydrochloride (CTC), trimethoprim (TMP), chloramphenicol (CMP), and erythromycin (ETM) to luciferase of Vibrio Qinghaiensis sp.-Q67 (Q67) by using toxicity testing combined with molecular docking, molecular dynamics, and binding free energy analysis. The curve categories for ENR were different from the other four antibiotics, with ENR being J-type and the rest being S-type, and the toxicity of these five antibiotics (pEC50) followed the order of ENR (7.281) > ETM (6.814) > CMP (6.672) > CTC (6.400) > TMP (6.123), the order of toxicity value is consistent with the the magnitude of the binding free energy (ENR (−47.759 kcal/mol), ETM (−46.821 kcal/mol), CMP (−42.905 kcal/mol), CTC (−40.946 kcal/mol), TMP (−28.251 kcal/mol)). The van der Waals force provided the most important contribution to the binding free energy of the five antibiotics in the binding system with Q67 luciferase. Therefore, the dominant factor for the binding of antibiotics to luciferase was shape compensation. The face-to-face π-π stacking interaction between the diazohexane structure outside the active pocket region and the indoles structure of Phe194 and Phe250 in the molecular structure was the main reason for the highest toxicity value of antibiotic ENR. The hormesis effect of ENR has a competitive binding relationship with the α and β subunits of luciferase. Homology modeling, molecular docking, molecular dynamics simulations and binding free energy calculations were used to derive the toxicity magnitude of different antibiotics against Q67, and insights at the molecular level. The conclusion of toxicological experiments verified the correctness of the simulation results. This study contributes to the understanding of toxicity mechanisms of five antibiotics and facilitates risk assessment of antibiotic contaminants in the aquatic environment.

Fluorescence quenching determination of tetracyclines based on the synergistic oxidation effect between Fe3O4 nanoparticles and tetracyclines

In recent years, tetracyclines (TCs) is a hot research topic. Herein, we report an interesting discovery using the complexation of oxytetracycline and metal ions. In this study, according to the properties of Fe3O4 nanoparticles (Fe3O4 NPs) as a nanoenzyme, it can be used to catalyze the oxidation of KI by H2O2 to produce while at the same time binds to rhodamine 6G (Rh6G) to form a conjoined particle (Rh6G ∼ I3)n, leading to a decrease in the fluorescence intensity of Rh6G. However, in the presence of TCs, Fe3O4 NPs have a synergistic effect with TCs, leading to enhanced catalytic activity, as well as better selectivity compared to the activity of other reducing enzymes. Consequently,the fluorescent signal based on a resonance scattering effect between Rh6G and is dependent on the concentration of TCs, thus achieving highly facile and robust detection of TCs. The limits of detection (LOD) of the method were 20 nM, 10 nM and 40 nM for oxytetracycline(OTC), tetracycline(TC) and chlortetracycline(CTC), respectively. Most importantly, the method can be successfully applied to the detection of TCs in milk, eggs, and honey. The recoveries of spiked samples ranged from 83.11 to 118.95%. Thus, a stable, hands-on strategy for the detection of TCs is proposed, which has potential applications in the field of food safety and environmental protection.

Effects of dietary polyherbal mixtures on growth performance, antioxidant capacity, immune function and jejunal health of yellow-feathered broilers

This study aimed to investigate the effects of polyherbal mixtures (PHM) on growth performance, antioxidant capacities, immune function, and intestinal health in yellow-feathered broilers. PHM is composed of five traditional Chinese medicine herbs (Portulaca oleracea L., Radix Sophora flavescens, Thalictrum glandulosissimum, Terra flava usta, and Pogostemon cablin). A total of 270 one-day-old yellow-feathered broilers were randomly allotted into 3 treatments for a 42-d feeding trial, each with 6 replicates of 15 birds. The dietary treatments consisted of a basal diet (CON), a basal diet supplemented with 50 mg/kg chlortetracycline (CTC), and a basal diet supplemented with 1000 mg/kg PHM. The results showed that dietary PHM supplementation increased body weight, ADG, and decreased F/G compared to the CON. PHM also increased spleen index and mRNA expression of IL-4 (d 21), and thymus index, serum IgA (d 42) and IgG, IL-4 and sIgA in jejunal mucosa (d 21 and 42), but decreased serum IFN-γ and mRNA expression of IFN-γ (d 21 and 42). In addition, PHM increased serum SOD, GSH-Px (d 21 and 42) and T-AOC (d 42), but decreased the content of serum MDA (d 21), the up-regulated mRNA expression of GSH-Px, CAT (d 21), SOD and CAT (d 42). Furthermore, PHM also improved the intestinal epithelial barrier indicators by the up-regulated mRNA expression of CLDN-1, OCLN (d 21 and 42) and ZO-1 (d 21), and the increased of villus height and villus height to crypt depth in jejunum (d 42). The high-throughput sequencing results showed that dietary PHM supplementation increased the alpha diversity and relative abundance of Oscillospira and Ruminococcus (d 21) and Lactobacillus (d 42), whereas decreasing that of Enterococcus (d 21) compared with CON. PICRUSt analysis revealed that metabolic pathways of carbohydrate, energy, lipid, cofactors, and vitamins were significantly enriched in the PHM group. Spearman's correlation analysis revealed that the genera Lactobacillus, Enterococcus, Ruminococcus, Oscillospira, and Faecalibacterium were related to growth performance, intestinal integrity, immune-related factors, antioxidant indices, and tight junction proteins. In conclusion, the results indicated that dietary PHM supplementation improved growth performance and immune status of yellow-feathered broilers by enhancing antioxidant capacities, barrier function, and modulated jejunal microbial communities. PHM used in our study has the potential to replace prophylactic antibiotic use in poultry production systems.

In-situ constructed indirect Z-type heterojunction by plasma Bi and BiO2-X–Bi2O2CO3 co-modified with BiOCl@Bi–MOF for enhanced photocatalytic efficiency toward antibiotics

Currently, the chemical properties of metal–organic frameworks (MOFs) can be fully exploited by combining inorganic semiconductors with MOFs to improve their narrow light absorption range and high carrier separation efficiency. Therefore, in this paper, indirect Z-type multicomponent Bi/BiO2-X–Bi2O2CO3/BiOCl@Bi–MOF heterojunction with plasma Bi and BiO2-X–Bi2O2CO3 co-modified with BiOCl@Bi–MOF were successfully prepared through combining hydrothermal and photodeposition methods using BiOCl@Bi–MOF composites as active carriers. The ability to remove chlortetracycline (CTC) with Bi/BiO2-X–Bi2O2CO3/BiOCl@Bi–MOF was investigated by modulating the factors, such as photodeposition time, presence or absence of MOF structure, different water source, and different inorganic salts. In the CTC degradation experiments, the optimized Bi/BiO2-X–Bi2O2CO3/BiOCl@Bi–MOF-10-0.3 composite showed the best photocatalytic degradation efficiency (94.6%) within 90 min of full-spectrum light illumination. Its corresponding first-order kinetic rate constant (0.0315 min−1) was 2.5 and 1.6 times higher than those of MOF-free structural composites Bi/BiO2-X–Bi2O2CO3/BiOCl-10-0.3 and BiOCl@Bi–MOF, respectively. The increased photocatalytic activity is attributed to the synergistic effect between the MOF structure, metal Bi, BiO2-X–Bi2O2CO3, and BiOCl@Bi–MOF carrier. By combining the results of active species capture experiments, electron spin resonance techniques (EPR), and photoelectrochemical experiments, we have deduced a possible indirect Z-type heterojunction photocatalytic mechanism between Bi, BiO2-X–Bi2O2CO3 and BiOCl@Bi–MOF. The possible photocatalytic degradation pathways and products of CTC were deduced by combining liquid chromatography-mass spectrometry (LC-MS). This work supplies valuable guidance for preparing metal nanoparticles/semiconductor/MOFs with an indirect Z-type heterojunction photocatalyst for the repair of natural CTC wastewater.

Construction of dual-channel ratio sensing platform and molecular logic gate for visual detection of oxytetracycline based on biomass carbon dots prepared from cherry tomatoes stalk

In this work, blue carbon dots (Stalk-Trp CDs) with high fluorescence quantum yield were successfully prepared from biological waste cherry tomato stalk and tryptophan. The morphology, composition, and properties of Stalk-Trp CDs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, infrared spectroscopy, ultraviolet–visible absorption spectroscopy, and fluorescence spectroscopy. On this basis, a dual-channel ratio sensing platform (Stalk-Trp CDs@Eu) was constructed using the interaction of Stalk-Trp CDs with Eu3+, which reduced the detection limit of the antibiotic oxytetracycline from 0.15 µmol/L to 0.018 µmol/L. Channel 1 of the dual-channel ratio sensing platform is a neutral environment (pH = 6.5), and the specific response of the probe to OTC causes its fluorescence to change from blue to purple. Channel 2 is an alkaline environment (pH = 11.5), and the fluorescence of the probe turns green only in the presence of OTC. The interaction mechanism of the dual-channel ratio sensing platform with the antibiotics oxytetracycline (OTC), chlortetracycline (CTC), and tetracycline (TC) was also revealed. The detection results of OTC in honey and milk by using Stalk-Trp CDs@Eu were highly consistent with the HPLC method recommended by the national standard. This shows that the dual-channel ratio sensing platform has great practical application value in the field of antibiotic detection.

Shaddock peels derived multilayer biochar with embedded CoO@Co nanoparticles for peroxymonosulfate based wastewater treatment

The utilization of bio-wastes, such as shaddock peels, is of great significance for sustainable development. Combined with the potential of peroxymonosulfate (PMS) based advanced oxidation process (AOP) in wastewater treatment, a highly efficient functional catalyst, derived from shaddock peels biochar (SPC) and embedded with CoO@Co nanoparticles, i.e. Co-SPC-x(y), was prepared using a facile impregnation-calcination method and used for refractory organics degradation with PMS.The decoration amount of Co and annealing temperature were optimized, and the effects of various reaction factors were investigated. The results indicated that the optimized sample of Co-SPC-10 (900) consisted of multilayer biochar with curly edges and highly dispersed CoO@Co nanoparticles in the range of 20–200 nm, which is in cubic metallic Co and CoO. Moreover, it also possessed a specific surface area of 248.6 m2/g, and exhibited excellent PMS activation ability with ∼100% chlortetracycline hydrochloride (CTC) removal ratio within only 12 min of operation. The Co-SPC-10 (900)/PMS system showed relatively high tolerance for HPO42−, NO3− and SO42−, while the Cl− and HA had considerable effects on it. Mechanism exploration results revealed that both radical and non-radical pathways existed in the Co-SPC-10 (900)/PMS system, in which the multilayered biochar functioned as an electron transfer carrier to facilitate the continuous cycle of Co2+/Co3+ in the CoO@Co nanoparticles by reacting with the absorbed CTC and PMS, resulting in the production of •OH, SO4•−, O2•− and 1O2. Additionally, the Co-SPC-10 (900) also showed good stability and catalytic oxidation performance for various refractory organics.

Degradation of Oxytetracycline and Chlortetracycline by Fenton Process

In this study, degradation of oxytetracycline (OTC) and chlortetracycline (CTC) was investigated by Fenton process. In experimental studies conducted for this purpose, different values of pH, Fe2+ concentration, H2O2 concentration and reaction time were tested as important parameters for the Fenton process and optimum conditions for OTC and CTC removal were determined. For both antibiotics, the optimum values of the parameters in the Fenton process were the same, and these values were found to be 3 for pH, 20 mg/L for Fe2+ concentration, 25 mg/L for H2O2 concentration, 5 min for reaction time. Under these optimum conditions, OTC degradation was 100%, CTC degradation was 99.68%, chemical oxygen demand (COD) removal efficiency for oxytetracycline (O-COD) was 89.6%, COD removal efficiency for chlortetracycline (C-COD) was 88.5%. These results show that the Fenton process is an effective method that can be used for OTC and CTC degradation.

Two luminescent phosphonate metal-organic framework as highly efficient and sensitive sensors for the detections of tetracycline antibiotic in aqueous system

The adverse effects of tetracycline (TC), chlortetracycline (CTC) and oxytetracyline (OTC) residues on human health and ecosystem have attracted much attention. Herein, two novel luminescent phosphonate metal-organic frameworks based on Zn and Cd were prepared by hydrothermal method, named MOF-1 (2[Zn2‧L·(H2O)2]) and MOF-2 (2[Cd(H2L)‧(H2O)2]), respectively. Two MOFs can specifically recognize three antibiotics and quench the fluorescence by the internal filter effect (IFE). In addition, in the presence of ions and other antibiotics, the MOFs still showed good selectivity and strong anti-interference performance. It is worth noting that the detection limits of MOF-2 for TC, CTC and OTC are 4.9, 1.21 and 2.17 ​nM respectively. These excellent sensing properties, together with easy preparation, good stability and feasibility, makes MOFs have high potential to detect tetracycline antibiotics in aqueous solution.

Effects of Clostridium butyricum as an Antibiotic Alternative on Growth Performance, Intestinal Morphology, Serum Biochemical Response, and Immunity of Broilers

The current study aimed to investigate the effects of Clostridium butyiricum on growth performance, intestinal morphology, serum biochemical response, and immunity in broiler chickens. A total of 330 commercial one-day-old, mixed-sex Ross 308 broilers were randomly divided into five treatment groups with six replicates per group. The broilers were fed the basal diet (CON), the basal diet with 150 mg/kg of aureomycin (AM), the basal diet with C. butyricum at 2 × 108 CFU/kg (CBL), the basal diet with C. butyricum at 4 × 108 CFU/kg (CBM), and the basal diet with C. butyricum at 8 × 108 CFU/kg (CBH). Results showed that the final body weight (BW) (p < 0.01; p < 0.05), ADG from day 22 to 39 (p < 0.05), and ADG from day 1 to 39 (p < 0.01; p < 0.05) were improved in a linear and quadratic response with the inclusion of C. butyricum. There were no differences in feed conversion rate (FCR) among all groups (p > 0.05). Supplementation with C. butyricum quadratically reduced the crypt depth at day 21 (p < 0.01), linearly improved the villus height in the jejunum at day 39 (p < 0.001), and linearly and quadratically increased the villus height to crypt depth (V/C) ratio in the jejunum at day 21 (p < 0.01) and day 39 (p < 0.01; p < 0.001). Dietary C. butyricum affected the thymus index at day 21 and day 39 (linear, p < 0.01), and the bursa of Fabricius index at day 39 (quadratic, p < 0.05). Compared to the AM group, the serum urea contents were decreased (p < 0.05) but the IgG contents were increased in the CBL and CBH groups at day 21 (p < 0.01); in addition, serum albumin (ALB) concentrations in all the C. butyricum-supplemented groups (p < 0.01) and IgG concentrations in the CBM group were augmented at day 39 (p < 0.05). In conclusion, dietary C. butyricum could enhance growth performance by improving jejunal morphology and stimulating immunity organ development in broilers, and could be an alternative to antibiotics in poultry feeds.

Efficient degradation of chlortetracycline in water by ultrasound activation of flexible ZnCoO doped PVDF membranes with high β phase

Piezo-catalysis technology is considered an emerging technology to remove organic pollutants from wastewater. In this study, a ZnCoO@PVDF membranes with high-voltage electrical properties was prepared for the piezo-catalytic degradation of chlortetracycline (CTC) in wastewater. The entry of Co into the main lattice of ZnO changes the electrical properties of ZnO. The d33 test shows that Co increases the piezoelectric coefficient of ZnO by 6.5 times. Under ultrasonic conditions, the Zn0.8Co0.2O@PVDF membranes exhibit the best piezo-catalytic activity, with a degradation rate constant of 0.2027 mM−1, which is 34.94 times higher than that of pure PVDF. At the same time, the doping of Zn0.8Co0.2O caused the change of the crystal form of PVDF, the β phase with piezoelectric properties increased significantly, and the piezoelectric coefficient increased from 27.3 pC/N of PVDF to 44.7 pC/N. Multiple by-products and degradation pathways were identified using LC-MS, and two main degradation pathways were proposed based on density functional theory (DFT) calculations. The toxicity of CTC and its by-products was estimated using Toxicity Estimation Software Tool (TEST) software, which further confirmed the reduction of environmental risk after piezoelectric catalytic degradation. This study provides new insights into the efficient piezo-catalytic treatment of antibiotic wastewater.

New insight into adsorption and co-adsorption of chlortetracycline hydrochloride and ciprofloxacin hydrochloride by Ga-based metal-organic gel/sodium alginate composite beads

Due to the extensive usage of tetracyclines and fluoroquinolones for disease control, their residuals usually coexist in wastewater and seriously affect human health and the entire ecosystem. To mitigate this problem, developing efficient and recyclable absorbent has been urgently required to be put on the agenda. In this research, Ga-based MOGs (GMOGs) were synthesized to remove chlortetracycline hydrochloride (CTC) and ciprofloxacin hydrochloride (CIP) in aqueous solution, followed by incorporating GMOGs into low-cost sodium alginate (SA) matrix to gain GMOG/SA beads with enhanced adsorption property, fine recycling performance and stable reusability. In single system (S-system), the adsorption behaviors of CTC/CIP by GMOGs and GMOG/SA beads including key operating factors, kinetics, isotherms and practicability were investigated systematically, and the maximum adsorption capacities for CTC/CIP by GMOGs and GMOG/SA beads achieved 406.50/158.23 mg g−1 and 1085.19/862.07 mg g−1, respectively. Furthermore, the proposed adsorption mechanisms were discussed. In binary system (B-system), regardless of suppressed co-adsorption behaviors of CTC/CIP by GMOGs and GMOG/SA beads arising from the competitive effect between CTC and CIP, their adsorption capacities still reached 207.90/126.90 mg g−1 and 588.24/571.42 mg g−1, respectively. Moreover, the value of industrial application was evaluated by testing the adsorption performance of GMOG/SA beads in bead columns and real water. This work provides a potential practicable, effective and recycled exploration of GMOG/SA beads for remediating the CTC and CIP co-contaminated wastewater.

Potential output and risk of commonly administered veterinary antibiotics from small-scale livestock farms to surrounding areas in Northwest China

The concern over antibiotic pollution from animal husbandry has significantly increased over recent years. However, few studies on output and environmental risk of veterinary antibiotics (VAs) throughout different exposure matrices from small-scale livestock farms (SSLFs) have been explored. This study explored the output and environmental risk of three classes of VAs (sulfonamides (SAs), tetracyclines (TCs), fluoroquinolones (FQs)) in three different types of environmental media (manure, soil, and plants/vegetables) derived from four livestock feedlots in the Hexi Corridor of Northwest China. Following, a risk assessment was conducted to identify the hazardous potential of these VAs on the ecological health of the surrounding environment. A total of 108 soil, 36 manure, 12 plants/vegetables, and 15 animal product samples were collected from the animal feedlots for analysis. The results showed that each of the three groups of VAs were detected in the soil, manure and plant samples derived from all four feedlots in varying levels. In the soil samples, the detection rate of SAs (68%) was higher than the TCs (57%) and the FQs (27%). The total concentration of VAs ranged from not detected (n.d.) to 275 ng/g, while chlortetracycline (CTC) was the most abundant (275 ng/g) of the VAs in soil samples. The SAs had the highest detection rate (100%), followed by TCs (89%), and FQs (78%) in manure samples. The total concentration of VAs residues ranged from n. d. to 105 ng/g, of which CTC was as high as 91 ng/g in manures. In the plant/vegetable samples, the TCs had the highest detection rate (58%), while sulfamethazine (SDM) was the most abundant (32 ng/g). The total concentration of the VAs ranged from n. d. to 65 ng/g in the plant/vegetable samples. The target VAs were not detected in animal products. Measurements of the composition of VAs in soil samples at different vertical depths as well as horizontal distances from the manure accumulation sites showed that VAs were partially retained in the soil of the feedlots and were distributed into the surrounding environment both horizontally and vertically. It is suspected that the detected VAs could be accumulated in agricultural soils since they could be found in most of the sampled manures and soils in SSLFs. These results highlighted the necessity of considering SSLF practices to mange the accumulation and disposal of manure mitigating and controlling VA pollution.

Facile synthesis of Fe-doped Zn-based coordination polymer composite with enhanced visible-light-driven activity for degradation of multiple antibiotics

We developed the novel Fe-doped Zn-based coordination polymer (CP) composites (Fe@Zn-CP-n, n = 1–3) with superior visible-light-driven photocatalytic activity. Herein, the Fe@Zn-CP composites were prepared using a newly designed Zn-CP {[Zn(3-padpe)(1,3-BDC)]·H2O}n using mixed ligands 4,4′-bis(3-pyridylformamide)diphenylether (3-padpe) and 1,3-benzenedicarboxylic acid (1,3-H2BDC) and FeSO4 by a facile approach at room temperature. The degradation of several tetracyclines (TCs), such as chlortetracycline (CTC), tetracycline hydrochloride (TC), and oxytetracycline (OTC) under visible-light irradiation were used to assess the photocatalytic performance. The generated ideal Fe@Zn-CP-2 composite showed high photocatalytic activity under visible light irradiation, for which the removal rate of antibiotics were 90.60% for CTC in 100 min, 90.00% for TC in 100 min, and 87.70% for OTC in 30 min, respectively. The superior photocatalytic performance was attributed to the Fe–O bond formation which expanded the optical absorption range and significantly increased the separation effectiveness of photogenerated charges. These properties enhanced the photoactivity of Fe@Zn-CP-2 for photocatalytic reaction under visible light irradiation. Additionally, the Fe@Zn-CP-2 showed excellent photostability and recycleability. The detailed intermediates and pathway of CTC degradation were also illustrated. According to the quenching studies and electron spin resonance (ESR) spectra characterization, the main species involved in the photocatalytic reaction were the radicals h+ and O2–. In addition, the possible photocatalytic reaction mechanisms were deeply discussed. This work offers fresh insight into the design of CP-based photocatalytic materials and demonstrates the broad application potential of Fe@Zn-CP composites in environmental remediation.

Degradation of tetracyclines by peracetic acid and UV/peracetic acid: Reactive species and theoretical computations

As an environment-friendly oxidant and disinfectant, peracetic acid (PAA) and PAA based-advanced oxidation processes (AOPs) for the treatment of emerging micropollutants have raised increasing interest, owing to their ease of activation and less generation of harmful disinfection byproducts. Tetracyclines (TCs) antibiotics as a group of wide-spectrum antibiotics are frequently detected in sewage effluents, while the knowledge of PAA-based advanced oxidation reactions to remove the substrates is quite limited. In this work, we systematically investigated the kinetics and underlying transformation mechanisms of three TCs including tetracycline (TTC), oxytetracycline (OTC), and chlortetracycline (CTC) in the UV-activated PAA oxidation process. The results indicated that three TCs can be efficiently decayed by UV/PAA. The pseudo-first-order reaction rate constants (kobs) of TCs followed the order: kCTC (0.453 min−1) ≫ kTTC (0.164 min−1) > kOTC (0.158 min−1). Quenching experiments showed that the removal of CTC was mainly ascribed to the direct oxidation of PAA, while TTC and OTC were more susceptible to free radicals. The kobs values of the three TCs by PAA oxidation presented a fairly well correlation to the global nucleophilicity and the activation energies of the TC molecules, highlighting the structure-specific reactions of TCs to PAA. Based on product identification and theoretical calculation, N-demethylation and hydroxylation were proposed as the main pathways for TCs degradation by PAA non-radical oxidation. The combination of PAA and UV irradiation can further improve the degradation efficiency of TCs and contribute to reducing the diffusion and transmission of resistance genes in the environment.

The Adsorption of CTC onto CFBs: A Study on Fabrication of Magnetic Cellulose/Fe3O4 Beads (CFBs) and Adsorption Kinetics.

Magnetic cellulose/Fe3O4 beads (CFBs) were fabricated by dispersing Fe3O4 particles in a microcrystalline cellulose (MCC) matrix. The CFBs were characterized by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), energy dispersive X-ray spectrometry (EDS), Brunauer-Emmett-Teller (BET) analysis and scanning electron microscopy (SEM). The adsorption behaviors of CFBs were studied by chlortetracycline hydrochloride (CTC) adsorption experiments. By means of adsorption kinetics and isotherms, the adsorption mechanisms were explored. The results show that quasi-spherical CFBs with a BET surface area as high as 119.63 m2/g were successfully tailored, with the high saturation magnetization (Ms > 40 emu/g) guaranteeing the magnetic separation of CFBs from wastewater. The process of adsorbing CTC onto CFBs involves monolayer chemical adsorption, and the maximum adsorption capacity for CTC estimated by the Langmuir model is 89.53 mg/g. The CFB product shows better adsorption performance in acidic solution than in basic solution.

Effect of pH on Adsorption of Tetracycline Antibiotics on Graphene Oxide.

Graphene oxide (GO) has good dispersibility and adsorption capacity for antibiotics adsorption, a complex process influenced by many factors. In this work, the adsorption mechanism of GO on tetracycline antibiotics at different pH was studied to address its attenuated effects on the microbial growth. The results showed that the adsorption process of GO on three antibiotics, namely, tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC), followed the pseudo-second-order kinetic model. The maximum adsorption capacities were observed at pH5 which were 133.0 mg/g for TC, 125.4 mg/g for OTC, and 167.0 mg/g for CTC. Furthermore, the reaction was uniform adsorption with a single layer on the surface of GO, and heating was conducive to the reaction. In the microbial growth experiment, the growth of E. coli and B. subtilis senses was optimal at pH5, which was consistent with the adsorption experiment. This study analyzed the effect of pH on the adsorption of antibiotics by GO and provided a theoretical basis for the further application of GO in various aquatic environments.

Nitrogen−doped−CQDs/schwertmannites as visible−light−responsive Fenton catalysts for the degradation of chlortetracycline and related cytotoxicity

The heterogeneous photo−Fenton method is a promising technology for wastewater treatment based on the development of efficient catalysts through which the inefficient Fe(III)/Fe(II) cycles and low utilization of H2O2 are optimized. In this work, viable heterogeneous photo−Fenton catalysts (NCS) are synthesized by in situ compounding nitrogen−doped carbon quantum dots (N−CQDs) with schwertmannite (SCH). Specifically, the NCS catalysts exhibit greatly enhanced capacity for chlortetracycline (CTC) degradation, in comparison with those of the pristine SCH and N−CQDs, with a remarkable efficiency of 95.12% at a wide pH range (3.0–7.0). In particular, this allows an efficient Fe(III)/Fe(II) conversion due to the fast electron transport capability provided by N−CQDs, coupled to an excellent structural stability of the catalysts. Main active species including •OH, •O2− and 1O2 are identified in the degradation process, and a possible degradation mechanism is tentatively proposed. In addition, related cytotoxicity of CTC degradation intermediates is verified via co−culturing with E. coli. This study provides a new strategy to overcome the disadvantages of photo−Fenton processes and develop new technologies for advanced water treatment.

A stable luminescent Cd(II) coordination polymer for selective detection of chlortetracycline in aqueous medium

A 1D zigzag chain Cd(II) coordination polymer (CP), [Cd(L)2(tcpa)]n(1) (L = 1,3-bis(2-methylbenzimidazol-1-yl)-2-propanol, H2tcpa = tetrachloroterephthalic acid) was hydrothermally synthesized and characterized. 1 can be a promising fluorescence probe to detect chlortetracycline (CTC) with a limit of detection of 2.3 × 10−8 mol/L. 1 could be reused five times. Further, the fluorescent sensing mechanism of 1 was discussed.

Soil Bacterial Community Tolerance to Three Tetracycline Antibiotics Induced by Ni and Zn

A laboratory work has been carried out to determine the tolerance of soil bacterial communities to Ni and Zn and co-tolerance to tetracycline antibiotics (chlortetracycline (CTC), oxytetracycline (OTC) and tetracycline (TC)) in soils individually spiked with five different concentrations of Ni or Zn (1,000, 750, 500, 250, and 125 mg kg−1), and an uncontaminated (0 mg kg−1) control soil. The PICT parameter (pollution-induced community tolerance) was estimated for the bacterial community using the tritium (3H)-labeled leucine incorporation technique, and the values corresponding to log IC50 were used as toxicity index. The mean log IC50 values observed in the uncontaminated soil samples indicate that Zn (with log IC50 = −2.83) was more toxic than Ni (log IC50 = −2.73). In addition, for the soil with the lowest carbon content (C = 1.9%), Ni-contaminated samples showed increased tolerance when the Ni concentrations added were ≥500 mg kg−1, while for the soils with higher carbon content (between 5.3% and 10.9%) tolerance increased when Ni concentrations added were ≥1,000 mg kg−1. Regarding the soils contaminated with Zn, tolerance increased in all the soils studied when the Zn concentrations added were ≥125 mg kg−1, regardless of the soil carbon content. The co-tolerance increases obtained after exposure of the bacterial suspension to TC, OTC and CTC showed an identical behavior within these tetracycline antibiotics. However, it was dependent on the heavy metal tested (Ni or Zn). In the case of soils 1 (C = 1.1%) and 2 (C = 5.3%), the soil bacterial communities showed increases in co-tolerance to TC, OTC and CTC for Ni concentrations added of ≥125 mg kg−1, while for soil 3 (with C = 10.9%) co-tolerance took place when Ni was added at ≥1,000 mg kg−1. However, in soils contaminated with Zn, increases in co-tolerance to CTC, OTC and TC occurred at Zn concentrations added of ≥125 mg kg−1 for the 3 soils tested. These results can be considered relevant when anticipating possible environmental repercussions related to the simultaneous presence of various types of pollutants, specifically certain heavy metals and antibiotics.