An exploration of the effect and interaction mechanism of bisphenol A on waste sludge hydrolysis with multi-spectra, isothermal titration microcalorimetry and molecule docking

Plasticizers inhibit food waste anaerobic digestion performance by affecting microbial succession and metabolism

The widely existed plastic additives plasticizers in organic wastes possibly pose negative influences on anaerobic digestion (AD) performance, the direct evidence about the effects of plasticizers on AD performance is still lacking. This study evaluated the influencing mechanism of two typical plasticizers bisphenol A (BPA) and dioctyl phthalate on the whole AD process. Results indicated that plasticizers addition inhibited methane production, and the inhibiting effects were reinforced with the increase of concentration. By contrast, 50 mg/L BPA exhibited the strongest inhibition on methane production. Physicochemical analysis showed plasticizers inhibited the metabolism efficiency of soluble polysaccharide and volatile fatty acids. Microbial communities analyses suggested that plasticizers inhibited the direct interspecies electron transfer participators of methanogenic archaea (especially Methanosarcina) and syntrophic bacteria. Furthermore, plasticizers inhibited the methane metabolisms, key coenzymes (CoB, CoM, CoF420 and methanofuran) biosynthesis and the metabolisms of major organic matters. This study shed light on the effects of plasticizers on AD performance and provided new insights for assessing the influences of plasticizers or plastic additives on the disposal of organic wastes.

Interacting with luteinizing hormone receptor provides a new elucidation of the mechanism of anti-androgenicity of bisphenol S

Bisphenol S (BPS) exhibited inhibitory effects on androgen synthesis, but its target of action remains unclear. We investigated the effects of BPS exposure at environmentally relevant concentrations (1 μg/L, 10 μg/L and 100 μg/L) for 48 h on androgen synthesis in rat ovarian theca cells and explored the underlying mechanisms, target site and target molecule. The results showed that BPS exposure inhibited the transcript levels of steroidogenic genes and reduced the contents of androgen precursors, testosterone and dihydrotestosterone. BPS exposure decreased the phosphorylation levels of extracellular signal-related kinase 1/2 (ERK1/2), and the inhibitory effects of BPS on testosterone content and steroidogenic gene expression were blocked by ERK1/2 agonist LY2828360, suggesting that ERK1/2 signaling pathway mediates the inhibitory effects of BPS on androgen synthesis. BPS mainly accumulated on the cell membrane, impermeable BPS-bovine serum albumin exposure still inhibited androgen synthesis, BPS interacted with rat luteinizing hormone receptor (LHR) via formation of hydrogen bonds in the transmembrane region, and the inhibitory effects of BPS on ERK1/2 phosphorylation were blocked by luteinizing hormone (the natural agonist of LHR), indicating that LHR located on the cell membrane is the target of action of BPS. This paper provides a new elucidation of the mechanism of anti-androgenicity of BPS, especially for the non-genomic pathways.

New strategies for evaluating imidacloprid-induced biological consequences targeted to Eisenia fetida species and the corresponding mechanisms of its toxicity

Imidacloprid (IMI), a neonicotinoid insecticide, has a wide variety of applications in both agriculture and horticulture. As a result of it massive and repeated use, its traces remained in soil pose severe damage to soil invertebrates, particularly earthworms. Limited information is available regarding the underlying mechanisms of IMI toxicity toward earthworms at the molecular, transcriptional, and cellular levels. Here, Eisenia fetida coelomocytes and key defensive proteins were selected as targeted receptors to explore the toxic mechanisms of oxidative stress-mediated cytotoxicity, genotoxicity, and antioxidant responses induced by IMI stress and the molecular mechanisms underlying the binding of IMI and superoxide dismutase (SOD)/catalase (CAT). Results showed that IMI exposure destroyed the cell membrane integrity of earthworm cells, causing cell damage and cytotoxicity. The intracellular levels of ROS, including ·O2- and H2O2 were induced by IMI exposure, thereby triggering oxidative stress and damage. Moreover, IMI exposure attenuated the antioxidative stress responses (reduced antioxidant capacity and CAT/SOD activities) and caused deleterious effects (enhanced DNA damage, lipid peroxidation (LPO), and protein carbonylation (PCO)) through ROS-mediated oxidative stress pathway. Aberrant gene expression associated with oxidative stress and defense regulation, including CAT, CRT, MT, SOD, GST, and Hsp70 were induced after IMI exposure. Concentration-dependent conformational and structural alterations of CAT/SOD were observed when IMI binding. Also, direct binding of IMI resulted in significant inhibition of CAT/SOD activities in vitro. Molecular simulation showed that IMI preferred to bind to CAT active center through its direct binding with the key residue Tyr 357, while IMI bound more easily to the connecting cavity of two subunits away from SOD active center. In addition, hydrogen bonds and hydrophobic force are the main driving force of IMI binding with CAT/SOD. These findings have implications for comprehensive evaluation of IMI toxicity to soil eco-safety and offer novel strategies to elucidate the toxic mechanisms and pathways of IMI stress.

Molecular interaction mechanisms and cellular response of superoxide dismutase and catalase to fluoranthene

As an important raw material and intermediate product of the petrochemical industry, fluoranthene (Fla) can be emitted with industrial activities and has become a typical polycyclic aromatic hydrocarbon enriched in the Chinese topsoil layer, posing a significant threat to sensitive soil biota. Here, multispectral tools and molecular simulation techniques were integrated to elucidate the molecular mechanism of Fla interaction with key antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) at the molecular level. Meanwhile, we further revealed the cellular responses of SOD and CAT and the associated redox states in earthworm (Eisenia fetida) coelomocytes based on the molecular-level results. Our results showed that the exposure to Fla affected the backbone structure of SOD and CAT molecules and resulted in the formation of Fla-SOD polymers as well as an overall reduction in the size of the Fla-CAT binding system. Fla altered the microenvironment around Tyr residues in the SOD molecule and quenched the endogenous fluorescence of Tyr within the CAT molecule. In earthworm coelomocytes, Fla at 60 and 80 μM resulted in a significant elevation of CAT and SOD activities by 114% (p = 0.032) and 6.09% (p = 0.013), respectively. Molecular simulation results suggested that Fla-induced changes in the structure and conformation of SOD and CAT may be the key reason for their altered activities. The related redox homeostasis detection in earthworm coelomocytes indicated that high concentrations (80 μM) of Fla led to a significant accumulation of intracellular ROS (p = 0.018) and resulted in the development of lipid peroxidation. Our work contributes to an in-depth understanding of the biological effect of Fla to sensitive soil fauna, thus providing new ideas for Fla ecological risk prevention and control.

Iron-loaded sludge biochar alleviates the inhibitory effect of tetracycline on anammox bacteria: Performance and mechanism

The anaerobic ammonia oxidation (anammox) process is sensitive to environmental pollutants, such as antibiotics. In this study, the harmful effect of tetracycline (TC) on the performance of an anammox reactor and the mitigation of TC inhibition by iron-loaded sludge biochar (Fe-BC) were studied by analyzing extracellular polymeric substances (EPS), microbial community structure and functional genes. The total inorganic nitrogen (TIN) removal rate of the TC reactor was reduced by 5.86% compared to that of the control group, while that of the TC + Fe-BC reactor improved by 10.19% compared to that of the TC reactor. Adding Fe-BC increased the activity of anammox sludge by promoting the secretion of EPS (including protein, humic acids and c-Cyts). The results of the enzymolysis experiment showed that protein can improve the activity of anammox sludge, while the ability of polysaccharide to improve the activity of anammox was related to the treated enzymes. In addition, Fe-BC alleviated the inhibitory effect of TC by mediating the anammox electron transfer process. Furthermore, Fe-BC increased the absolute abundance of hdh and hzsB by 2.77 and 1.18 times compared to the TC reactor and improved the relative abundance of Candidatus Brocadia in the absence of TC. The addition of Fe-BC is an effective way to alleviate the inhibitory effect of TC on the anammox process.

A review on mechanistic understanding of microplastic pollution on the performance of anaerobic digestion

Anaerobic digestion (AD) has emerged as a promising technology for diverting the organic waste from the landfills along with the production of clean energy. AD is a microbial-driven biochemical process wherein the plethora of microbial communities participate in converting the putrescible organic matter into biogas. Nevertheless, the AD process is susceptible to the external environmental factors such as presence of physical (microplastics) and chemical (antibiotics, pesticides) pollutants. The microplastics (MPs) pollution has received recent attention due to the increasing plastic pollution in terrestrial ecosystems. This review was aimed for holistic assessment of impact of MPs pollution on AD process to develop efficient treatment technology. First, the possible pathways of MPs entry into the AD systems were critically evaluated. Further, the recent literature on the experimental studies pertaining to the impact of different types of MPs at different concentrations on the AD process was reviewed. In addition, several mechanisms such as direct exposure of MPs on the microbial cells, indirect impact of MPs through the leaching of toxic chemicals and reactive oxygen species (ROS) formation on AD process were elucidated. Besides, the risk possessed by the increase of antibiotic resistance genes (ARGs) after the AD process due to the MPs stress on microbial communities were discussed. Overall, this review deciphered the severity of MPs pollution on AD process at different levels.

Glyoxylate cycle maintains the metabolic homeostasis of Pseudomonas aeruginosa in viable but nonculturable state induced by chlorine stress

Bacteria enter a viable but non-culturable (VBNC) state with low metabolic activity to cope with environmental stress (e.g., chlorine disinfection). Elucidating the mechanism and key pathway of VBNC bacteria maintaining low metabolic competence is of great significance to realize their effective control and reduce their environmental and health risks. This study discovered that the glyoxylate cycle is a key metabolic pathway for VBNC bacteria, but not for culturable bacteria. And blocking the glyoxylate cycle pathway inhibited the reactivation and led to the death of VBNC bacteria. The main mechanisms involved the breakdown of material and energy metabolism and the antioxidant system. Gas chromatography-tandem mass spectrometry analysis showed that blocking the glyoxylate cycle led to a disruption of carbohydrate metabolism and fatty acid catabolism in VBNC bacteria. As a result, the energy metabolism system of VBNC bacteria collapsed and the abundance of energy metabolites (ATP, NAD⁺ and NADP⁺) decreased significantly. Moreover, the decrease in the level of quorum sensing signaling molecules (quinolinone and N-Butanoyl-D-homoserine lactone) inhibited the synthesis of extracellular polymeric substances (EPSs) and biofilm formation. And the downregulation of glycerophospholipid metabolic competence increased the permeability of cell membranes, leading to the entry of large amounts of hypochlorous acid (HClO) into the bacteria. In addition, the down-regulation of nucleotide metabolism, glutathione metabolism, and the reduction of antioxidant enzyme content resulted in the inability to scavenge reactive oxygen species (ROS) generated by chlorine stress. The large production of ROS and the reduction of antioxidants together led to the breakdown of the antioxidant system of VBNC bacteria. In short, the glyoxylate cycle is the key metabolism pathway of VBNC bacteria for stress resistance and maintaining cellular metabolic balance, and targeting the glyoxylate cycle represents an attractive strategy for developing new and efficient disinfection methods for the control of VBNC bacteria.

Metabolism differences of biofilm and planktonic Pseudomonas aeruginosa in viable but nonculturable state induced by chlorine stress

More than 95% of the bacteria in environment are viable but nonculturable (VBNC). However, it is difficult to elucidate directly the metabolic characteristics of these VBNC bacteria and the differences between biofilm-VBNC bacteria and planktonic-VBNC bacteria. In this study, VBNC P. aeruginosa induced by chlorine was used to clarify the metabolism characteristics and mechanism of differential metabolism between biofilm-VBNC bacteria and planktonic-VBNC bacteria. Results showed that P. aeruginosa in biofilm state was more likely to enter VBNC state. The mechanisms of differential metabolism were involved in the difference of reactive oxygen species production owing to the protection of extracellular polymers. ¹⁵N and ²H labeled single-cell Raman spectra directly proved that VBNC state bacteria still maintained low material and energy metabolism, and the metabolic activity of biofilm-VBNC P. aeruginosa was lower than that of planktonic-VBNC P. aeruginosa. GC-MS/MS analysis showed 51 metabolites with significant differences. KEGG analysis showed that the types and contents of extracellular metabolites from P. aeruginosa in VBNC states were significantly lower than those in the culturable state (p < 0.05), mainly involving in citrate cycle, glutathione metabolism, phenylalanine metabolism, tyrosine metabolism and fatty acid degradation. Also, the contents of most extracellular metabolites from P. aeruginosa in biofilm-VBNC state were lower than those in VBNC planktonic state. The significant differences (p < 0.05) were mainly involved in alanine, aspartate and glutamate metabolism, glycolysis/gluconeogenesis, D-Alanine metabolism and glycerophospholipid metabolism. The result of this research was favorable to the accurate identification of VBNC bacteria, the health risk assessment and scientific control of harmful VBNC bacteria.

Development of a horseradish peroxidase-Fenton-like system for the degradation of sulfamethazine under weak acid condition

Both horseradish peroxidase (HRP) and ferrous ion (Fe²⁺) can degrade organic micropollutants (e.g., sulfamethazine) in the presence of hydrogen peroxide (H₂O₂), but they have their own disadvantages, such as low degradation efficiency and low pH condition, respectively. In order to overcome the above shortcomings, this study is to develop a HRP-Fenton-like system for sulfamethazine (SMR) efficient degradation by analyzing the optimal reaction conditions, degradation mechanisms, and effect of ions. Results show that HRP and Fe²⁺ achieve effective coupling by adding trace Fe²⁺ (≤ 10 μmol/mL) to the HRP system at pH = 5, and the degradation rate of SMR increased by 20.7-42% depending on Fe²⁺ concentration compared with single HRP treatment. Consumption of H₂O₂ and quenching of hydroxyl radicals confirmed that HRP dominated SMR removal in the HRP-Fenton-like system. HPLC-MS analysis shows that SMR was degraded by C-S bond breaking, N-S bond breaking, hydroxyl substitution, and rearrangement. Furthermore, Cl^-, HCO₃^-, and NO₃^- exhibit an acceptable negative effect, while SO₄^2- shows a positive effect on the degradation of SMR.

Organism and molecular-level responses of superoxide dismutase interaction with 2-pentanone

2-Pentanone is an excellent organic solvent and extractant, which is widely used in industrial production. 2-Pentanone is harmful to soil organisms when it enters the soil. However, current studies have not clarified the response of the antioxidant enzyme superoxide dismutase (SOD) to 2-Pentanone and its mechanism. In this study, the response of earthworm antioxidant enzyme SOD to 2-Pentanone and its molecular mechanism was investigated at organism molecular levels. The results showed that the SOD activity of earthworms under 2-Pentanone stress was significantly inhibited, and the inability of superoxide anion radicals (·O₂^-) to be scavenged in time might be one of the reasons for the increase of lipid peroxidation. Under 2-Pentanone exposure conditions, catalase (CAT), an antioxidant enzyme closely related to SOD, and the total antioxidant capacity (T-AOC) of earthworms were activated to resist oxidative damage. On the other hand, the observation of earthworm microstructure provided evidence of a direct risk of 2-Pentanone on earthworm body wall tissues. Molecular-level assays have shown that 2-pentanone altered the secondary structure of SOD, which further led to the loosening of the SOD backbone structure and the extension of the polypeptide chain. On the other hand, 2-pentanone quenched the endogenous fluorescence of SOD in the form of static quenching and formed the 2-pentanone/SOD complex. Molecular simulation results suggested that 2-pentanone tended to bind on the surface of SOD rather than close to the active site, and it is speculated that the alteration of SOD structure is the key reason for the change in its activity. This study enriches the toxicological data of 2-Pentanone on soil organisms, thus responding to the current concerns about its ecological risk.

Recent Progress and Prospects in Catalytic Water Treatment

Presently, conventional technologies in water treatment are not efficient enough to completely mineralize refractory water contaminants. In this context, the implementation of catalytic processes could be an alternative. Despite the advantages provided in terms of kinetics of transformation, selectivity, and energy saving, numerous attempts have not yet led to implementation at an industrial scale. This review examines investigations at different scales for which controversies and limitations must be solved to bridge the gap between fundamentals and practical developments. Particular attention has been paid to the development of solar-driven catalytic technologies and some other emerging processes, such as microwave assisted catalysis, plasma-catalytic processes, or biocatalytic remediation, taking into account their specific advantages and the drawbacks. Challenges for which a better understanding related to the complexity of the systems and the coexistence of various solid-liquid-gas interfaces have been identified.

Occurrence, effects, and biodegradation of plastic additives in sludge anaerobic digestion: A review

The retention of microplastics, a complex blend of polymers and plastic additives (PAs), in municipal sludge has been reported. The inevitable release of PAs from microplastics might affect the subsequent biological disposal of sludge, and their final fate are of great public concern. Therefore, this review describes the current knowledge in the occurrence of PAs in sludge and significant advances in their effects on sludge anaerobic digestion (AD) and their biodegradation performance. Specifically, the compositions and contents of plasticizers, stabilizers, and flame retardants in sludge worldwide are systematically summarized. The discrepant impacts of PAs on hydrolysis, acidification, and methanogenesis processes are analyzed and compared, with corresponding trends deduced. Furthermore, the biodegradation performances of PAs during sludge AD are also discussed. For most of the PAs detected in sludge, available data for their fate and effects on AD is yet limited. Moreover, the potential role of AD microbes in the release of PAs from microplastics was still unknown. Especially, the potential effects of PAs released from biodegradable microplastics on sludge AD and their fate should be of concern. The obtained knowledge would update our understanding of the risk assessment and control of PAs in sludge AD. Recommendations for future investigation are made.

Toxic effect and mechanism of ultrafine carbon black on mouse primary splenocytes and two digestive enzymes

This paper investigated the toxic effect and mechanism of ultrafine carbon black (UFCB) on splenocytes and enzymes in the digestive system. It was found that the toxicity of UFCB to splenocytes was dose-dependent. UFCB with a low concentration (<15 μg/mL) had no significant effect on splenocytes while UFCB with high concentration (>15 μg/mL) induced significant oxidative damage with increased content of reactive oxygen species (ROS) (134%) and malonaldehyde (MDA) (222.3%) along with the decreased activity of superoxide dismutase (SOD) (55.63%) and catalase (CAT) (87.73%). Analysis combined cellular and molecular levels indicated that UFCB induced splenocyte toxicity through oxidative stress. The interactions of UFCB with two important digestive enzymes, α-amylase and lipase, were also studied respectively. Results showed that the interaction of UFCB and the two enzymes altered the particle size and fluorescence intensity in both experimental systems. The formation of protein corona also resulted in the contraction of the polypeptide skeleton in both enzymes, which further inhibited their activity. Our work provided basic data on the toxicity of UFCB in the spleen and digestive system and fills the gap in the study of UFPs toxicity. CAPSULE: UFCB induced splenocyte toxicity and enzyme dysfunction through oxidative stress and protein corona formation respectively.

Toxicity assessment of Fluoranthene, Benz(a)anthracene and its mixed pollution in soil: Studies at the molecular and animal levels

An increasing amount of Fluoranthene (Fla) and Benz(a)anthracene (BaA) is being produced and used, eventually entering the soil sediments. The accumulation of Fla and BaA will cause poisoning to typical enzymes (α-Amylase) and organisms (Eisenia fetida) in soil. However, the studies about exploring and comparing the different effects of Fla, BaA and their joint effect at different levels are rarely reported. In this paper, the different effects of Fla, BaA and their mixed pollutant on α-Amylase were evaluated and compared at the molecular level, and the effect of Fla-BaA to the antioxidant system of earthworm (Eisenia fetida) was investigated from the aspects of concentration and exposure time at the animal level. The results showed that Fla-BaA had the greatest influence on the skeleton structure and the microenvironment of amino acid residue of α-Amylase compared to Fla and BaA, and in the mixed pollutant system, the joint effect mode was additive mode. The inhibitory effect of Fla-BaA on the activity of α-Amylase was also stronger than that of the system alone. The assays at the animal level showed that low concentrations (below 5 mg/kg) of Fla-BaA increased the activity of GSH-Px and SOD while high concentrations inhibited their activity. The POD that was activated throughout the experiment period suggested its key role in the earthworm antioxidant system. Changes in T-AOC and MDA showed that long-term and high-dose of Fla-BaA exposure inhibited the antioxidant capacity of Eisenia fetida, causing lipid peroxidation and damage to cells.

Probing the single and combined toxicity of PFOS and Cr(VI) to soil bacteria and the interaction mechanisms

Many research focused on the removal of perfluorooctane sulfonic acid (PFOS) and hexavalent chromium (Cr(VI)) in some industrial wastewater (e.g. electroplating wastewater), but few research reported the combined toxicity of PFOS and Cr(VI) to soil bacteria. Therefore, the toxicity and mechanisms of the combined PFOS and Cr(VI) to bacteria (with Bacillus subtilis as a model) are explored. The results show that the combined PFOS and Cr(VI) exhibits much higher toxicity to the bacteria than that of Cr(VI) alone. The growth profile of Bacillus subtilis exposed by the combined pollution decreased by 18% and 56%, respectively, compared with that of single Cr(VI) and the control, indicating the combined toxicity to Bacillus subtilis is synergistic. Moreover, the changes of EPSs in Bacillus subtilis, such as decreased potential, increased extracellular polysaccharides, decreased extracellular proteins and irregular morphology, also confirmed that the combined PFOS and Cr(VI) caused greater toxicity. The increase of intracellular ROS and permeability of dye 4', 6-diamidino-2-phenylindoledihydrochloride (DAPI) suggest that oxidative damage and increased membrane permeability are the main mechanisms of toxicity induced by the combined PFOS and Cr(VI). This work could provide useful information for the risk assessment of co-exposure to PFOS and heavy metals in the natural environment.

Bisphenol A attenuation in natural microcosm: Contribution of ecological components and identification of transformation pathways through stable isotope tracing

Residues of bisphenol A (BPA) are ubiquitously detected in the surface water due to its widespread usage. This study systematically investigated the dissipation and kinetics of BPA under simulated hydrolysis, direct and indirect photolysis, bacterial degradation, microbial degradation and natural attenuation in microcosm. Structural equation modeling (SEM) by using partial least square method in path coefficient analysis suggested that the microbial degradation was the major factor involved in the natural attenuation of BPA. The potential transformation products were identified by using liquid chromatography high-resolution mass spectrometry (LC-HRMS) and stable isotope tracing technique by simultaneous performing gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) and gas chromatography mass spectrometry (GC-MS). A total of fourteen including three novel transformation products of BPA were identified to indicate five possible pathways. An increased yield of labeled (δ¹³C) CO₂ and detection of ¹³C-labeled phospholipid fatty acids (PLFAs) indicated the mineralization of BPA and possible utilization of BPA or its transformation products by microbes for cellular membrane synthesis, respectively.

Single and combined effects of amino polystyrene and perfluorooctane sulfonate on hydrogen-producing thermophilic bacteria and the interaction mechanisms

As a carrier of perfluorooctane sulfonate, nano-plastics are ubiquitous and finally enriched in the sludge, which is widely used as a raw material for the production of bioenergy (hydrogen or methane) by anaerobic digestion. However, there are still many unknowns about their metabolic toxicity to functional microbes (e.g. hydrogen-producing thermophilic bacteria). Therefore, single and combined effects of amino polystyrene (NPS: 70 nm; 0.2 mg/L) and perfluorooctane sulfonate (PFOS: 0.1, 1 and 5 mg/L) on hydrogen-producing thermophilic bacteria were investigated after exposure for 7 days at 55 °C and pH = 5.7. Single NPS exhibited obvious interference to the metabolism of thermophilic bacteria, resulting in a 53.9% reduction in hydrogen production. However, the combined NPS + PFOS produced an antagonistic effect, leading to a 31.6% reduction in hydrogen production. Nonetheless, the single and combined exposure did not alter the type of hydrogen production (acetic acid-type hydrogen fermentation). Moreover, single NPS and combined NPS + PFOS not only induced the changes of the composition of extracellular polymers (EPSs) and π bond structure of the protein in EPSs, but also decreased the activity of hydrolase in EPSs and surface charge of EPSs. Compared to single NPS exposure, NPS + PFOS-exposed thermophilic bacteria was less permeable to a semi-membrane permeable dye and produced less reactive oxygen species, but were still significantly higher than control group. In short, the main mechanisms of single NPS and combined NPS + PFOS were both to increase cell permeability and to induce oxidative stress. The addition of PFOS alleviated the toxic effect of NPS, but did not change its mechanism of toxicity.

Effects of Bisphenol A on Foxl2 gene expression and DNA damage in adult viviparous fish Goodeaatripinnis

Bisphenol A (BPA) is an emerging pollutant of global concern. Viviparous fish Goodea atripinnis is endemic to the Central Mexican Plateau where BPA was detected; however, few studies examined the influence of this chemical on native viviparous fish. The effects of BPA (sublethal dose) were determined on DNA integrity and Foxl2 expression in G. atripinnis gonads, and interactions of BPA with FOXL2 protein. Genotoxicity analysis revealed that % comets, at 14 and 28 days and comet tail length (at 14 days) were significantly higher in exposed compared to controls. In general, the % DNA tail was not markedly higher in BPA-treated fish; however, tail moment related to tail length exhibited significant increases in DNA damage. RT-qPCR assays showed Foxl2 overexpression after 14 and 28 days of exposure in females; while in males, Foxl2 was overexpressed after 28 days. In silico analysis demonstrated that BPA interacted with seven residues located in FOXL2 homeodomain. In summary, sublethal BPA doses induced DNA damage and changes in Foxl2 expression in gonadal cells of G. atripinnis, which may adversely affect reproduction in BPA-exposed wild populations. Foxl2 overexpression and BPA-FOXL2 interaction suggested alterations in processes involving Foxl2. Viviparous fish may thus serve as potential non-conventional models for assessing pollutants effects.

Evaluation of single and combined toxicity of bisphenol A and its analogues using a highly-sensitive micro-biosensor

Bisphenol analogues have been developed as alternatives to bisphenol A (BPA), a common chemical with potential adverse effects on human health. It is imperative to perform a fast and sensitive evaluation for the toxicity of these bisphenol analogues. This study introduces a label-free electrochemical biosensor based on a screen-printed electrode modified with the carboxylated multi-walled carbon nanotube/rhodamine B/gold nanoparticle. Ctenopharyngodon idella kidney (CIK) cells were used as the biological recognition agent to detect changes in electrochemical signals and indicate the cell viability. Only 20 μL of sample was required for detection, which was much lower than that of other conventional electrochemical methods (≥ 1 mL). This biosensor was examined for the cytotoxicity of BPA, bisphenol AF (BPAF), bisphenol B (BPB), bisphenol F (BPF), and bisphenol S (BPS) to CIK cells. The half inhibition concentration (IC₅₀) values after 48 h of exposure indicated that the rank order of cytotoxicities was BPAF > BPB > BPA > BPF > BPS. The morphological changes in CIK cells after treatment with various bisphenols were investigated, and the combined toxicities of the binary bisphenol mixtures were determined. Potentially synergistic and additive effects were observed. These findings provide new insights into the cytotoxicity of bisphenol analogues.

Insights into thermodynamic mechanisms driving bisphenol A (BPA) binding to extracellular polymeric substances (EPS) of activated sludge

Bisphenol A (BPA) in wastewater has high risks of causing biological feminization. During the wastewater treatment process, large amounts of BPA are accumulated in activated sludge. However, the mechanisms of BPA interacted with activated sludge are still unclear. Especially, the roles of extracellular polymeric substances (EPS), which are major components of activated sludge, in the removal of BPA have never been concerned. In this study, the binding interactions between sludge EPS and BPA are explored combining fluorescence spectroscopy and dynamic light scattering. The thermodynamic mechanisms driving the binding behavior of BPA to EPS are illustrated by isothermal titration calorimetry. The results indicate that the binding interaction between BPA and EPS is spontaneous. BPA mainly binds with the proteins of EPS by hydrophobic association. The random-coiled structure of EPS transforms into relatively condensed cores after binding with BPA. A neutral pH, high ionic strength, and high temperature promote the binding process, facilitating to stabilize BPA in sludge EPS. This study provides new insights into the roles of sludge EPS in the migration and removal of BPA in activated sludge system.

In vitro assessment of the toxicity of small silver nanoparticles and silver ions to the red blood cells

This work reports the toxicity of small silver nanoparticles (nanoAg, 20 nm) and silver ions (Ag⁺) to the red blood cells with the silver concentration level of 10^-6 g/mL. Results show that red blood cells (RBCs) start hemolysis when treated by nanoAg of 1.5 × 10^-5 g/mL or Ag⁺ of 2.9 × 10^-7 g/mL. A low ATPase activity of 30% has been observed after RBCs being treated with Ag⁺ of 2.6 × 10^-7 g/mL, while the nanoAg does not obviously affect the ATPase activity. In molecular level, Ag⁺ is more toxic to the amino acid residues than nanoAg according to the change of fluorescence characteristics of hemoglobin (Hb). However, the nanoAg has been found to be more toxic than Ag⁺ to the secondary structure of Hb in terms of the loss of α-helix content.

Exploration on the Interaction Ability of Antitumor Compound Bis-[2,6-difluoro-N-(hydroxyl-<κ>O)benzamidato-<κ>O]dibutylitin(IV) with Human Peroxisome Proliferator-Activated Receptor hPPARγ

Diorganotin(IV) antitumor compound bis-[2,6-difluoro-N-(hydroxyl-<κ>O)benzamidato-<κ>O] (DBDF2,6T) was one of the novel patent organotin compounds with high antitumor activity and relatively low toxicity. In this study, several methods were used to study the interaction between DBDF2,6T and hPPARγ protein, including fluorescence quenching, three-dimensional (3D) fluorescence, drug affinity responsive target stability (DARTS), ultrafiltration-LC, and molecular docking. According to the experimental results, the quenching process of the hPPARγ protein was induced by static quenching mode to form a nonradiative ground-state complex with DBDF2,6T spontaneously, mainly through the hydrophobic force. DBDF2,6T could bind to the hPPARγ protein directly and give the protein the ability of antienzymatic hydrolysis. And the binding mode of DBDF2,6T into hPPARγ protein appeared to have an orientation towards residues of SER342 and GLY284. In conclusion, these methods could comprehensively reveal the interaction details of DBDF2,6T and the hPPARγ protein and established a feasible way to preliminarily identify the agonist compounds for the hPPARγ protein.