Integrated physio-biochemical and transcriptomic analysis reveals the joint toxicity mechanisms of two typical antidepressants fluoxetine and sertraline on Microcystis aeruginosa.

Selective serotonin reuptake inhibitor (SSRI) antidepressants are of increasing concern worldwide due to their ubiquitous occurrence and detrimental effects on aquatic organisms. However, little is known regarding their effects on the dominant bloom-forming cyanobacterium, Microcystis aeruginosa. Here, we investigated the individual and joint effects of two typical SSRIs fluoxetine (FLX) and sertraline (SER) on M. aeruginosa at physio-biochemical and molecular levels. Results showed that FLX and SER had strong growth inhibitory effects on M. aeruginosa with the 96-h median effect concentrations (EC50s) of 362 and 225 µg/L, respectively. Besides, the mixtures showed an additive effect on microalgal growth. Meanwhile, both individual SSRIs and their mixtures can inhibit photosynthetic pigment synthesis, cause oxidative damage, destroy cell membrane, and promote microcystin-leucine-arginine (MC-LR) synthesis and release. Moreover, the mixtures enhanced the damage to photosynthesis, antioxidant system, and cell membrane and facilitated MC-LR synthesis and release compared to individuals. Furthermore, transcriptomic analysis revealed that the dysregulation of the key genes related to transport, photosystem, protein synthesis, and non-ribosomal peptide structures was the fundamental molecular mechanism underlying the physio-biochemical responses of M. aeruginosa. These findings provide a better understanding of the toxicity mechanisms of SSRIs to microalgae and their risks to aquatic ecosystems.

Unraveling the combined toxicity and removal mechanisms of fluoxetine and sertraline co-contaminants by the freshwater microalga Chlorella pyrenoidosa.

Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (FLX) and sertraline (SER), are among the most widely detected pharmaceuticals in aquatic environments, and they usually occur as mixtures. However, little is known about the combined toxicity of SSRI mixtures to microalgae and the associated removal mechanisms. This study investigated the combined toxicity of FLX and SER to the growth, photosynthetic activity, and antioxidant system of Chlorella pyrenoidosa and their removal mechanisms. The results showed that FLX and SER strongly inhibited microalgal growth with 96 h EC50 values of 493 and 61.1 µg/L, respectively. Additionally, the combined toxicity of FLX and SER towards microalgal growth exhibited an additive effect. After 4 days of short-term exposure, FLX, SER, and their mixtures caused photosynthetic damage and oxidative stress in microalgae, and the mixture's toxicity was stronger than those of individuals. However, the adverse effects on microalgal growth, photosynthetic activity, and antioxidant system were alleviated with increasing exposure time. Meanwhile, C. pyrenoidosa efficiently removed FLX (67.59%-99.08%) and SER (94.92%-99.11%) individually after 11 days of cultivation. Biodegradation (59.25%-86.21%) was the prominent removal mechanism of FLX, while both biodegradation (48.08%-88.17%) and bioaccumulation (4.74%-43.38%) contributed significantly to SER removal. The co-existence of FLX and SER lowered the removal rate and biodegradation amount of both compounds. Besides, SER inhibited C. pyrenoidosa's N-demethylation and O-dealkylation of FLX, while co-existing with FLX inhibited the excretion of the N-deamination product of SER from microalgal cells. Furthermore, the principal component analysis indicated that the removal performance of FLX, SER, and their mixtures correlated strongly to the microalgae's physiological and biochemical states. These results highlighted the significance of co-contamination during ecological risk assessments and microalgae-based bioremediation of SSRIs.

Effective photodegradation of antibiotics by guest-host synergy between photosensitizer and bismuth vanadate: Underlying mechanism and toxicity assessment.

The removal of antibiotics in wastewater has attracted increasing attention. Herein, a superior photosensitized photocatalytic system was developed with acetophenone (ACP) as the guest photosensitizer, bismuth vanadate (BiVO4) as the host catalyst and poly dimethyl diallyl ammonium chloride (PDDA) as the bridging complex, and used for the removal of sulfamerazine (SMR), sulfadiazine (SDZ) and sulfamethazine (SMZ) in water under simulated visible light (λ > 420 nm). The obtained ACP-PDDA-BiVO4 nanoplates attained a removal efficiency of 88.9%-98.2% for SMR, SDZ and SMZ after 60 min reaction and achieved kinetic rate constant approximately 10, 4.7 and 13 times of BiVO4, PDDA-BiVO4 and ACP-BiVO4, respectively, for SMZ degradation. In the guest-host photocatalytic system, ACP photosensitizer was found to have a great superiority in enhancing the light absorption, promoting the surface charge separation-transfer and efficient generation of holes (h+) and superoxide radical (·O2-), greatly contributing to the photoactivity. The SMZ degradation pathways were proposed based on the identified degradation intermediates, involving three main pathways of rearrangement, desulfonation and oxidation. The toxicity of intermediates was evaluated and the results demonstrated that the overall toxicity was reduced compared with parent SMZ. This catalyst maintained 92% photocatalytic oxidation performance after five cyclic experiments and displayed a co-photodegradation ability to others antibiotics (e.g., roxithromycin, ciprofloxacin et al.) in effluent water. Therefore, this work provides a facile photosensitized strategy for developing guest-host photocatalysts, which enabling the simultaneous antibiotics removal and effectively reduce the ecological risks in wastewater.

Ecotoxicological effects of the antidepressant fluoxetine and its removal by the typical freshwater microalgae Chlorella pyrenoidosa.

The antidepressant fluoxetine (FLX) has gained increasing attention due to its frequent detection in aquatic environments and negative effects on non-target organisms. However, knowledge on the ecotoxicological effects of FLX and its removal by microalgae is still limited. In this study, the ecotoxicological effects of FLX (10 -1000 µg/L) were assessed using batch cultures of the freshwater microalgae Chlorella pyrenoidosa for 10 days based on changes in growth, antioxidant response, and photosynthetic process. The removal efficiency, removal mechanism, and degradation pathway of FLX by C. pyrenoidosa were also investigated. The results showed that the growth of C. pyrenoidosa was inhibited by FLX with a 4 d EC50 of 0.464 mg/L. Additionally, FLX significantly inhibited photosynthesis and caused oxidative stress on day 4. However, C. pyrenoidosa can produce resistance and acclimatize to FLX, as reflected by the declining growth inhibition rate, recovered photosynthetic efficiency, and disappearance of oxidative stress on day 10. Despite the toxicity of FLX, C. pyrenoidosa showed 41.2%- 100% removal of FLX after 10 days of exposure. Biodegradation was the primary removal mechanism, accounting for 88.2%- 92.8% of the total removal of FLX. A total of five metabolites were found in the degradation processes of FLX, which showed less toxicity than FLX. The main degradation pathways were proposed as demethylation, O-dealkylation, hydroxylation, and N-acylation. Our results not only highlight the potential application of microalgae in FLX purification, but also provide insight into the fate and ecological risk of FLX in aquatic environments.

Tumor homing-penetrating and nanoenzyme-augmented 2D phototheranostics against hypoxic solid tumors.

Tumor microenvironment (TME)-oriented nanomedicine emerges as an efficient routine to greatly improve the efficiency of cancer treatment. The typical feature of hypoxia in TME remains as the main obstacle of many therapeutics like photodynamic therapy. Herein, a specific two-dimensional (2D) phototheranostics (GO-MnO2@tLyP-1/Ce6, denoted as GMtC) with the function of oxygen self-producing and tumor barrier-breaking was detailed by integrating the nanoenzyme MnO2 colloids, tumor homing-penetrating peptide tLyP-1 and photosensitizer chlorin e6 (Ce6) to tackle the hypoxic tumors. GMtC was capable to accumulate into the inner of murine mammary 4T1 tumor spheroids (and the depth could be as far as 90 µm) and to relieve the hypoxia state by catalytic decomposition of endogenous H2O2 to oxygen, which subsequently enhanced the yield of cytotoxic singlet oxygen under laser irradiation. In vivo dual-modal imaging of magnetic resonance and biofluorescence demonstrated the targeted accumulation and distribution of GMtC in tumor regions, thus facilitating the tumor hypoxia alleviation. Notably, GMtC achieved the highest photodynamic anticancer efficiency against 4T1 tumors without obvious systemic toxicity compared with the non-penetrating and no oxygen-generating counterparts. This study suggests the great promise of GMtC as an endogenous TME-responsive and exogenous laser-triggered theranostic platform against the solid hypoxic tumors. STATEMENT OF SIGNIFICANCE: The hostile tumor hypoxia not only induces the tumor angiogenesis, invasiveness and irreversible metastasis, but also inherently impairs the efficiency of many therapeutic modalities like photodynamic therapy (PDT). Though numerous hypoxia-alleviating strategies based on nanomedicine have been proposed, little attention is paid to the hypoxia-specific transportation barriers. This study develops a type of 2D phototheranostics GMtC against hypoxic solid tumors by integrating the function of tumor homing-penetrating and in situ oxygen-generating. GMtC displays outstanding performance in tumor deep penetration to hypoxia center and generating abundant oxygen in responsive to tumor microenvironment, thus exerting the highest efficiency of PDT against 4T1 mammary tumor. GMtC can be a potent theranostics to treat the solid hypoxic tumors.

Functions and clinical significance of mechanical tumor microenvironment: cancer cell sensing, mechanobiology and metastasis.

Dynamic and heterogeneous interaction between tumor cells and the surrounding microenvironment fuels the occurrence, progression, invasion, and metastasis of solid tumors. In this process, the tumor microenvironment (TME) fractures cellular and matrix architecture normality through biochemical and mechanical means, abetting tumorigenesis and treatment resistance. Tumor cells sense and respond to the strength, direction, and duration of mechanical cues in the TME by various mechanotransduction pathways. However, far less understood is the comprehensive perspective of the functions and mechanisms of mechanotransduction. Due to the great therapeutic difficulties brought by the mechanical changes in the TME, emerging studies have focused on targeting the adverse mechanical factors in the TME to attenuate disease rather than conventionally targeting tumor cells themselves, which has been proven to be a potential therapeutic approach. In this review, we discussed the origins and roles of mechanical factors in the TME, cell sensing, mechano-biological coupling and signal transduction, in vitro construction of the tumor mechanical microenvironment, applications and clinical significance in the TME.

Light-responsive hyaluronic acid nanomicelles co-loaded with an IDO inhibitor focus targeted photoimmunotherapy against "immune cold" cancer.

Nanomedicine enabled cancer combination immunotherapy not only sufficiently activates the host immune system, but also reprograms the immunosuppressive microenvironment, representing a new generation approach to treat cancer. Herein, we demonstrated a targeted photo- and immune-active nanoplatform termed NLG919@HA-Ce6 to simultaneously elicit efficient immunogenic cell death (ICD) using the photosensitizer Ce6 and modulate the tryptophan metabolic pathway using an indoleamine 2,3-dioxygenase (IDO) inhibitor NLG919 for the combined photodynamic therapy (PDT) and checkpoint blockade immunotherapy. Against the triple-negative and poorly immunogenic 4T1 breast cancer model, the stable spherical nanomicelle NLG919@HA-Ce6 selectively killed tumour cells via the toxic singlet oxygen upon laser excitation, thus in situ triggering a potent antitumor immune response, as seen via the obvious CRT exposure, ATP release, dendritic cell maturation, etc. Meanwhile, the IDO1-mediated immunosuppression was effectively reprogrammed to an immunostimulatory phenotype, which was accompanied by an enhanced cytotoxic T cell response as well as reduced Treg infiltration in tumour bed. Ultimately, the 4T1 tumour was synergistically suppressed by NLG919@HA-Ce6 due to the outcome of focused PDT, obvious ICD post PDT and IDO1 blockade. This study suggests the promise of NLG919@HA-Ce6 as an alternative simple, stimulative and targeted nanoagent to enable the whole-body photo-immune therapy against "immune cold" cancer.

Effect of iron plaque on antibiotic uptake and metabolism in water spinach (Ipomoea aquatic Forsk.) grown in hydroponic culture.

Ferrous ion was added to the culture solution, followed by the introduction of tetracyclines (TCs), to explore the effect of iron plaque (IP) on the uptake and translocation of TCs by water spinach (Ipomoea aquatic Forsk.). The adsorption amount of TCs on the root surface positively correlated with the amount of IP, except for doxycycline and minocycline. The bioconcentration factor of TCs in roots increased and fitted well with the amount of IP. The concentration of TCs in acrial tissues was three to four orders of magnitude lower than that in roots, and the translocation factor of TCs also fitted well with the amount of IP in a negative linear relationship. Furthermore, IP significantly influenced the metabolism of TCs in water spinach. The accumulation of TC metabolites increased with the increment of IP in roots rather than in acrial tissues, which showed the significance of IP in the metabolism and accumulation of TCs in aquatic plants. Therefore, the metabolism of TCs should not be ignored if IP is induced on the root surface, and the distribution of metabolites should be taken into consideration for the risk assessment and antibiotic pollution control for aquatic plants.

Combined effects of environmentally relevant concentrations of diclofenac and cadmium on Chironomus riparius larvae.

The nonsteroidal anti-inflammatory drug diclofenac (DCF) is considered a contaminant of emerging concern. DCF can co-exist with heavy metals in aquatic environments, causing unexpected risks to aquatic organisms. This study aimed to assess the combined effects of DCF and cadmium (Cd) at environmentally relevant concentrations on the bioconcentration and status of oxidative stress and detoxification in Chironomus riparius larvae. The larvae were exposed to DCF (2 and 20 µg L-1) and Cd (5 and 50 µg L-1) alone or in mixtures for 48 h. The combined exposure to DCF and Cd was found to reciprocally facilitate the accumulation of each compound in larvae compared with single exposures. As indicated by the antioxidant enzyme activities, reduced glutathione levels, and malondialdehyde contents, the low concentration of the mixture (2 µg L-1 DCF + 5 µg L-1 Cd) did not alter the oxidative stress status in larvae, while the high concentration of the mixture (20 µg L-1 DCF + 50 µg L-1 Cd) induced stronger oxidative damage to larvae compared with single exposures. The expression levels of eight genes (CuZnSOD, MnSOD, CAT, GSTd3, GSTe1, GSTs4, CYP4G, and CYP9AT2) significantly decreased due to the high concentration of the mixture compared with single exposures in most cases. Overall, the results suggest that the mixture of DCF and Cd might exert greater ecological risks to aquatic insects compared with their individual compounds.

Mixed Germ Cell Tumor of the Endometrium: A Case Report and Literature Review.

Germ cell tumors (GCTs) localized extragonadally are rare, with only 14 reported cases of a yolk sac tumor in the endometrium. Here we report a case of mixed endometrium GCTs in a 65-year-old postmenopausal woman with abnormal vaginal bleeding. An ultrasound examination showed an oval-shaped mass in the patient's uterine cavity. Biochemical examination revealed elevated serum α-fetoprotein (AFP) at 359 ng/mL, whereas the tumor markers CA-125, CA-199, and CEA were all within normal range. Total hysterectomy and bilateral salpingo-oophorectomy were performed;. a histological examination revealed that the malignant components contained a yolk sac tumor, embryonal carcinoma, and focal immature teratoma. Immunohistochemical staining showed that AFPs were diffusively distributed in both the yolk sac tumor and embryonal carcinoma. The stem cell marker OCT3/4 was positive in the embryonal carcinoma component and that the pan-cytokeratin AE1/AE3 staining was positive in glandular areas. GFAPs (Glial Fibrillary Acidic Proteins) were positive in neuroectodermal tubules; the Ki-67 protein was positive in 90% of the tumor cells, whereas CD117 and placental alkaline phosphatase (PLAP) were negative. The cumulative evidence indicated mixed GCTs of endometrium as the final histopathological diagnosis. The patient received three courses of adjunct chemotherapy that provided good therapeutic efficacy as evidenced by the decreased serum AFP level. Our report on this rare case of mixed GCTs of the endometrium, supported by associated histological patterns and immunophenotypes and successful adjunct chemotherapy after surgery, could provide insight on future treatment of this rare but lethal disease.

Interactive effects of diclofenac and copper on bioconcentration and multiple biomarkers in crucian carp (Carassius auratus).

Diclofenac (DCF), a non-steroidal anti-inflammatory drug, is widespread in aquatic environments and coexists with heavy metals to form combined pollution. However, the interactive effects of DCF and heavy metals on aquatic organisms remain unknown. This study aimed to investigate the interactive effects of DCF and copper (Cu) on the bioconcentration, oxidative stress status and detoxification-related gene expression in crucian carp (Carassius auratus). Fish were exposed to Cu (100 µg L-1) and DCF (1, 10, 100 and 1000 µg L-1) alone or in combination for 7 days. Results obtained showed that the treatment of Cu combined with high levels of DCF (100 and 1000 µg L-1) significantly decreased tissue concentrations of DCF and Cu compared to the correspondingly individual exposure. Concerning oxidative stress status, as reflected by the activities of antioxidant enzymes and malondialdehyde content, low exposure concentrations of DCF (1 and 10 µg L-1) seemed to mitigate the oxidative stress induced by Cu, whereas the co-exposure of Cu with the highest level of DCF (1000 µg L-1) led to stronger oxidative damage in fish liver than Cu exposure alone. With regarding to detoxification-related genes, in most cases, the expressions of cyp 1a, cyp 3a, gstα, gstπ, pxr and P-gp in crucian carp were significantly altered upon exposure to the compounds in combination compared to exposure to the compounds individually. Collectively, these findings indicate the capacity of each of these pollutants to alter bioconcentration potential, pro-oxidative effects and detoxification-related gene responses of the other when both co-occur at specific concentrations.

Removal of Tetracycline by Hydrous Ferric Oxide: Adsorption Kinetics, Isotherms, and Mechanism.

The removal of tetracycline (TC) from solution is an important environmental issue. Here we prepared an adsorbent hydrous ferric oxide (HFO) by adjusting a FeCl3·6H2O solution to neutral pH. HFO was characterized by a surface area analyzer, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), and was used to remove TC from solution. The influence of pH, solid-to-liquid ratio, ionic type, and strength on TC removal was investigated. Adsorption kinetics and isotherms were also determined. HFO after adsorption of TC was analyzed by FTIR and XPS to investigate the adsorption mechanism. The results showed that the adsorption of TC increased from 88.3% to 95% with increasing pH (3.0-7.0) and then decreased. K+ ions had little effect on TC adsorption by HFO. However, Ca2+ and Mg2+ reduced the adsorption of TC on HFO. When the concentrations of Ca2+ and Mg2+ were increased, the inhibitory effect was more obvious. Pseudo-second-order kinetics and the Langmuir model fitted the adsorption process well. The maximum adsorption capacity of TC on HFO reached 99.49 mg·g-1. The adsorption process was spontaneous, endothermic, and increasingly disordered. Combination analysis with FTIR and XPS showed that the mechanism between TC and HFO involved electrostatic interactions, hydrogen interactions, and complexation. Therefore, the environmental behavior of TC could be affected by HFO.

Effects of hydrodynamic disturbances on biodegradation of tetrabromobisphenol A in water-sediment systems.

Tetrabromobisphenol A (TBBPA) is an emerging contaminant and exists widely in river and lake systems due to its widespread use. In natural water-sediment systems, hydrodynamic disturbances always exist. However, few studies have investigated the mechanism of TBBPA biodegradation under the influence of water disturbances. In this paper, using a specialized type of racetrack-style flumes, the TBBPA biodegradation in water-sediment systems was studied under the influence of three typical hydrodynamic disturbances. The results of 5-week experiments showed that strong hydrodynamic disturbances greatly accelerate the TBBPA biodegradation rate of the water-sediment systems. The half-lives (T1/2) under static condition (SC) were approximately 40.2 days, and the T1/2 was reduced to 16.0 days under strong hydrodynamic condition (SHC). Furthermore, the physicochemical properties and corresponding bacterial communities under these conditions were investigated to help explain the TBBPA biodegradation mechanism. The results showed that strong currents could promote dissolved oxygen (DO) levels, increase nutrient concentrations, and reduce the bacterial diversity in the sediment. Meanwhile, due to the increase in DO and nutrient concentrations, the aerobic bacterial genera conducting TBBPA biodegradation showed rapid growth with strong water disturbances, while the growth of anaerobic bacterial genera was inhibited. Citrobacter, which was the most dominant degrading bacterial genus (0.6%-14.9% in water and 3.5%-17.4% in sediment), was closely related to water disturbances and may be linked to enhanced TBBPA biodegradation. Other minor degrading bacterial genera, such as Bacillus, Sphingomonas, Anaeromyxobacter, Geobacter, Clostridium, and Flavobacterium, were also found in these water-sediment systems. The findings from this study showed the importance of considering hydrodynamic disturbance in understanding TBBPA biodegradation in aquatic environments.

Interactive Effects of Sertraline and Diphenhydramine on Biochemical and Behavioral Responses in Crucian Carp (Carassius auratus).

The ecotoxicity of psychiatric pharmaceuticals to aquatic organisms is being increasingly recognized. However, current ecological studies focus on the effects of individual psychiatric pharmaceuticals, with little attention being given to their combined effects. In this study, the interactive effects of two psychiatric pharmaceuticals, sertraline (SER) and diphenhydramine (DPH), on bioconcentration and biochemical and behavioral responses were investigated in crucian carp (Carassius auratus) after seven days of exposure. DPH was found to increase the accumulation of SER in fish tissues relative to SER-alone exposure. In addition, the mixture of SER and DPH significantly changed the activities of antioxidant enzymes and led to significant increases in malondialdehyde content, relative to SER alone. Concerning the neurotoxicity, relative to SER-alone exposure, brain AChE activity was significantly enhanced in fish following the combined exposure. Regarding behavioral responses, swimming activity and shoaling behavior were significantly altered in co-exposure treatments compared with the SER alone. Moreover, the inhibition effects on the feeding rates were increased in co-exposure treatments compared to SER alone. Collectively, our results suggest that the mixtures of psychiatric pharmaceuticals may pose more severe ecological risks to aquatic organisms compared to these compounds individually.

Relative effects of wind-induced disturbances and vegetation on tetrabromobisphenol A cycling in shallow lakes: Direct and indirect effects.

The environmental concerns regarding the possible threats of tetrabromobisphenol A (TBBPA) to aquatic environments are increasing. However, information about TBBPA cycling in the water-vegetation-sediment systems of shallow lakes is limited. In a shallow lake, wind-induced disturbance is considered as the key factor of affecting the cycling of contaminants. To address this issue, the TBBPA distribution and elimination processes were simulated for three typical wind speeds by using an annular flume. Four forms of TBBPA were studied in these systems, including water, suspended solids (SS), vegetation and sediment. The results showed that the mass distributions of TBBPA in water, SS and vegetation increased remarkably while enhancing the wind-induced disturbances, which resulted from the release of TBBPA from the sediment through resuspension and adsorption-desorption processes. However, most of the TBBPA (up to 94%) still accumulated in the sediment. Wind-induced disturbances and vegetation both increased the TBBPA elimination rate in the water-vegetation-sediment systems. The half-life (T1/2) of TBBPA in the fast wind condition was 16.1 ±â€¯0.2 days, which was shorter than that in the static condition (29.8 ±â€¯0.9 days). Compared to the systems without vegetation, the presence of vegetation shortened the T1/2 by 7.3 days in the static condition. Furthermore, a structural equation model (SEM) was used to assess the direct and indirect effects of environmental factors on the TBBPA amounts in each form. The main effects of wind speed and vegetation in the TBBPA cycling of each form (except for the TBBPA on vegetation) were indirect by affecting the dissolved oxygen (DO), velocity and suspended solids concentration (SSC). Overall, the findings provide useful information about the fate of TBBPA and other related organic contaminants in shallow lake systems.

Preparation of Iron-Loaded Granular Activated Carbon Catalyst and Its Application in Tetracycline Antibiotic Removal from Aqueous Solution.

The removal of tetracycline antibiotics from water is currently an important environmental issue. Here we prepared an iron-loaded granular activated carbon catalyst (GAC-Fe) through a one-step calcination method to remove tetracycline antibiotics from aqueous solution. The GAC-Fe was characterized by Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. The effect of different influencing factors on the removal behavior of tetracycline antibiotics was studied, such as the solid-to-liquid ratio, H2O2 dosage, environmental temperature, initial pH, and contact time. The removal mechanism was explored through Fe ion dissolution and a free radical quenching experiment. The results show that the optimum solid-to-liquid ratio was 3.0 g∙L-1 and the suitable H2O2 dosage was 1.0 mL (3%). The applicable environmental temperature was 25 °C and the appropriate pH value was 2.0. The removal rate of tetracycline antibiotics tended to be stable in a contact time of 600 min. The main mechanism of tetracycline antibiotic removal by GAC-Fe was heterogeneous catalytic reaction through iron ion leaching and free radical inhibition experiment. The hydroxyl radical played a major role during the removal process. The partially dissolved iron ions initiated a homogeneous catalytic reaction. However, heterogeneous catalytic degradation was the main reaction. The GAC-Fe could still remove tetracycline antibiotics after five cycles, especially for methacycline and minocycline. Our work suggests that the GAC-Fe catalyst has potential as a remediation agent for tetracycline antibiotics in aqueous solution.

Bioconcentration and ecotoxicity of sulfadiazine in the aquatic midge Chironomus riparius.

Although sulfadiazine (SDZ) is widespread in aquatic environments, information regarding the effects of SDZ on aquatic insects is still limited. In the present study, the bioconcentration and the effects of SDZ on the antioxidant system and the expression of endocrine and stress-related genes in Chironomus riparius larvae were investigated. The larvae were exposed to SDZ at the nominal concentrations of 2, 20 and 200 µg/L for 48 h. The results showed that SDZ was taken up by C. riparius despite presenting low bioconcentration factor values (0.99-3.92). In addition, superoxide dismutase activity was markedly reduced compared with the control group, whereas the levels of malondialdehyde were not significantly affected by SDZ. Moreover, the mRNA expression of genes related to heat shock proteins (Hsp70 and Hsp27) and ecdysone pathway (EcR and E74) were significantly up-regulated following all SDZ treatments. In aggregate, our work provides novel and interesting results regarding the potential biochemical and genetic effects of SDZ on freshwater insects.

Bioconcentration, metabolism and the effects of tetracycline on multiple biomarkers in Chironomus riparius larvae.

The antibiotic tetracycline (TC) is widespread in surface waters, but few data are available regarding its adverse effects on aquatic insects. In this study, we investigated the bioconcentration, metabolism, and effects of TC on Chironomus riparius larvae exposed to different concentrations of TC (1.83, 18.5 and 174 µg L-1) for 48 h. The bioconcentration factors were 3.65, 0.74 and 0.23 in larvae with exposure to 1.83, 18.5 and 174 µg L-1 TC, respectively. High concentration ratios of the metabolites anhydrotetracycline (0.56-0.60), 4-epitetracycline (0.43-0.69), and 4-epianhydrotetracycline (0.50-0.55) to the unmetabolized compound were found. Additionally, the activities of superoxide dismutase and glutathione S-transferase were markedly inhibited with a significant increase in malondialdehyde contents at high exposure concentrations of TC (18.5 and 174 µg L-1). Moreover, significant up-regulation of heat shock genes (hsp70 and hsp27), the ecdysone receptor gene, and the E74 early ecdysone responsive gene was observed at all exposure concentrations except for hsp70 at 1.83 µg L-1. Collectively, these results suggested that TC was quickly absorbed and metabolized by C. riparius and resulted in molecular and biochemical disturbances.

Removal of tetracycline from aqueous solution by biochar derived from rice straw.

Antibiotic pollution has drawn considerable attention and the removal of antibiotic from water is crucial. In the present study, biochars were produced from rice straw under different pyrolytic temperatures of 300 °C, 500 °C, and 700 °C (RSBC300, RSBC500, and RSBC700, respectively). The biochars were used to remove tetracycline (TC) from aqueous solution and the influence of different experimental conditions on TC removal was investigated. The results showed that the order of adsorption was as follows: RSBC700 > RSBC500 > RSBC300. A pseudo-second-order model and Langmuir isotherm model described the adsorption process of TC on biochars. Maximum adsorption capacity could reach 50.72 mg g-1 at 35 °C based on Langmuir fitting. Initial pH of the solution had little influence on TC removal. The inhibitory effect of Ca2+ on TC removal was greater than that of Na+. High system temperature was beneficial for TC removal. Minerals in RSBC500 affected TC removal and minerals in RSBC300 and RSBC700 had little influence on TC removal. TC removal rate decreased from 58.86 to 27.84% when the minerals were removed from RSBC500. The main mechanism involved in high-temperature biochar and TC adsorption included EDA π-π interactions and electrostatic interactions. Therefore, high-temperature biochar derived from rice straw has the potential to act as an adsorbent to remove tetracycline from aqueous solution.

Effects of dissolved organic matter, feeding, and water flow on the bioconcentration of diclofenac in crucian carp (Carassius auratus).

Diclofenac (DCF), a prevalent anti-inflammatory drug, is frequently detected in aquatic organisms. However, little is known about the environmental factors that affect the bioconcentration of DCF in aquatic environments. Here, we firstly investigated the bioconcentration of DCF by crucian carp (Carassius auratus) following aqueous exposure (3.57, 14.5, and 71.8 µg L-1) for 21 days. DCF can accumulate in crucian carp, and the maximum bioconcentration factors (BCFs) of 121 L kg-1 in the liver, 52.3 L kg-1 in the gills, and 46.8 L kg-1 in the muscle were always found at 3.57 µg L-1 after 14 days of exposure. Secondly, the influences of dissolved organic matter (DOM), feeding, and water flow on the bioconcentration of DCF were determined at the nominal concentration of 4 µg L-1 for 14 days. The BCFs of DCF in various fish tissues decreased by 0.5-85% with the increasing DOM concentrations. Feeding also led to lower body burden of DCF in fish tissues (6-55%) with the increasing food amount. In hydrodynamic experiment, the BCFs of DCF decreased by15-57% at most in various fish tissues. Collectively, our results demonstrated the bioconcentration of DCF in fish can be influenced by various environmental factors, which should be considered in the risk assessment of pharmaceuticals.