Fluoride network and circular economy as potential model for sustainable development-A review

Fluoride recovery in degradable fluorinated polyesters

We report a new class of degradable fluorinated polymers through the copolymerization of tetrafluorophthalic anhydride and propylene oxide or trifluoropropylene oxide which show up to 20 times quicker degradation than the non-fluorinated equivalents and allow for fluoride recovery.

A tert-Butyldiphenylsilyl-Containing Polyimide-Based Chemosensor for Sequential Detection of Fluoride Ions and Trace Water in Organic Solvents

A tert-butyldiphenylsilyl-containing polyimide (PI-OSi) has been established as a colorimetric and ratiometric chemosensor for rapid detecting fluoride ions (F-). The UV-vis absorbance ratio value (A322/A288) of PI-OSi in a DMF solution displays a wide linear range change to F- concentrations with a detection limit (DL) value of 2.13 μM. Additionally, adding incremental amounts of F- to a DMF solution of PI-OSi shows an immediate color change to yellow and finally to green from colorless. More interestingly, the resulting PI-OSi plus F- system (PI-OSi·F) could detect trace water in DMF. The A292/A322 value of PI-OSi·F almost linearly increases with low water content, which suggests convenient quantitative sensing of trace water content in DMF. The DL value of PI-OSi·F for sensing water in DMF is determined to be 0.00149% (v/v). The solution color of PI-OSi·F returns to colorless when the water content increases, indicating that PI-OSi·F can conveniently estimate water content in DMF by naked-eye detection. The detection mechanisms confirmed by an 1H NMR study and a DFT calculation involve a F--induced desilylation reaction of PI-OSi to form phenolate anion followed by protonation with trace water. Finally, PI-OSi film was fabricated for the colorimetric detection of F- and water in CH3CN.

Fluorine in 20 vegetable species and 25 lettuce cultivars grown on a contaminated field adjacent to a brick kiln

Crops grown in areas contaminated by industrial and agricultural fluorine (F) have gained increasing attention, however F levels in different vegetables and lettuce cultivars are rarely reported. In situ-field experiment was designed to investigate the concentration, translocation, and health risks of F in 20 vegetable species and 25 lettuce cultivars. After the growth of 150 d for vegetables and 60 d for lettuce, F concentration (12.83-138.07 mg kg-1), translocation factor (0.16-6.32), and bio-concentration factor (1.90-13.73) varied significantly between vegetable species and lettuce cultivars. According to the hazard quotient values (based on the reference dose of F), all the vegetable species appears to pose no risk to human health, while 60% of the lettuce cultivars present potential health risks to children. Therefore, the limit value of F in vegetables for adults and children should be enacted in the future. Moreover, cabbage, green radish, spinach, leaf mustard, and Frisee lettuce (Huayu) were considered as a safe dietary product. These findings contributed to the safe cultivation of vegetables and the control of fluorosis in the areas contaminated by industrial and agricultural activities.

Nrf2/PINK1-mediated mitophagy induction alleviates sodium fluoride-induced hepatic injury by improving mitochondrial function, oxidative stress, and inflammation

Mitophagy has distinct functions, which can lead to either protection or damage of tissues. Though current evidence indicated that NaF triggers mitophagy, the role and regulation of mitophagy in sodium fluoride (NaF)-induced liver injury still remain unclear. Therefore, we exployed the cell and mouse models and confirmed that NaF treatment activates mitophagy. Knocking down PTEN-induced putative kinase protein 1 (PINK1) expression attenuated mitophagy and increased the degree of mitochondrial impairment, oxidative stress, and apoptosis in NaF-treated HepG2 cells. In vivo experiments indicated that PINK1 deficiency weakened NaF-induced mitophagy. Moreover, PINK1-deficient mices aggravated NaF-induced hepatic mitochondrial injury, oxidative stress, and inflammation in livers, evidenced by the increased number of abnormal mitochondria, decreased adenosine triphosphate (ATP) and glutathione (GSH) levels, elevated reactive oxygen species (ROS) and malondialdehyde (MDA) content, enhanced hepatic macrophage infiltration and inflammatory cytokine levels. Notably, NaF exposure activated Nrf2 signaling both in vitro and in vivo. Nrf2 siRNA transfection blocked the upregulation of PINK1 expression and the induction of mitophagy in NaF-treated HepG2 cells. Also, ML385 (Nrf2 inhibitor) partially blocked the upregulation of PINK1 expression caused by NaF in mice livers. To sum up, the present study provided the demonstration that Nrf2/PINK1-mediated mitophagy activation offers a hepatoprotective effect by inhibiting NaF-induced mitochondrial dysfunction, oxidative stress, and inflammation.

Choline alleviated perinatal fluoride exposure-induced learning and memory impairment through α4β2 nAChRs and α7 nAChRs in offspring mice

Fluoride pollution is widely present in the living environment. As a critical period of brain development, the perinatal period is extremely vulnerable to fluoride. Studies have found that choline can protect the brain's memory and enhance the ability to focus. However, the effect of choline on perinatal fluoride-induced nerve damage remains unclear. Therefore, 32 Kunming newly conceived female mice and their offspring mice were randomly divided into control, NaF, LC + NaF, and HC + NaF groups, and the HE staining, Y-maze test, RT-PCR, western blotting, immunohistochemistry, etc. were used in this study. The results showed that fluoride decreased the brain organ coefficients and brain protein content (p < 0.05, p < 0.01), and caused histomorphological damage in the hippocampus and cortex, which suggested that fluoride affected the development of the brain and damaged the brain. Moreover, the results of the Y-maze test showed that fluoride increased the number of learning days, error reaction time, and total reaction time, and decreased the AchE activity in the brain (p < 0.05, p < 0.01), which indicated that fluoride reduced the learning and memory ability of the mice. Besides, the results showed that fluoride decreased the mRNA and protein expression levels of α4β2 nAChRs and α7 nAChRs in the hippocampus and cortex (p < 0.05, p < 0.01). However, perinatal choline supplementation reversed the aforementioned fluoride-induced changes. In short, these results demonstrated that choline alleviated perinatal fluoride-induced learning and memory impairment, which will provide a rationale for the mitigation and prevention of fluoride-induced brain damage.

Fluoride subacute testicular toxicity in Wistar rats: Benchmark dose analysis for the redox parameters, essential elements and DNA damage

Excessive fluoride (F^-) levels in the environment could induce different pathological changes, including comorbidities in reproductive functions. Hence, the aim of the present in vivo study was to explore F^- subacute toxicity mechanisms via Benchmark dose (BMD) methodology on rat's testicles. The experiment was conducted on thirty male Wistar rats for 28 days, divided into six groups (n = 5): 1) Control (tap water); 2) 10 mg/L F^-; 3) 25 mg/L F^-; 4) 50 mg/L F^-; 5) 100 mg/L F^-; 6) 150 mg/L F^-. Testicles were dissected out and processed for the determination of F^- tissue concentrations, redox status parameters, essential elements level, and DNA damage. PROASTweb 70.1 software was used for determination of external and internal dose-response relationship. The results confirmed a significant increase in superoxide anion (O₂^.-), total oxidative status (TOS), copper (Cu), zinc (Zn), iron (Fe), DNA damage levels, and decrease in superoxide dismutase activity (SOD1) and total thiol (SH) groups. The dose-dependent changes were confirmed for SOD1 activity and DNA damage. The most sensitive parameters were SOD1 activity and DNA damage with the lowest BMDLs 0.1 μg F^-/kg b. w. Since human and animal populations are daily and frequently unconsciously exposed to F^-, this dose-response study is valuable for further research regarding the F^- health risk assessment.

Evaluation of Krill Meal in Commercial Diets for Juvenile Swimming Crab (Portunus trituberculatus)

An 8-week feeding trial was carried out to assess the effect of dietary krill meal on growth performance and expression of genes related to TOR pathway and antioxidation of swimming crab (Portunus trituberculatus). Four experimental diets (45% crude protein and 9% crude lipid) were formulated to obtain different replacements of fish meal (FM) with krill meal (KM); FM was replaced with KM at 0% (KM0), 10% (KM10), 20% (KM20), and 30% (KM30); fluorine concentration in diets were analyzed to be 27.16, 94.06, 153.81, and 265.30 mg kg^-1, respectively. Each diet was randomly divided into 3 replicates; ten swimming crabs were stocked in each replicate (initial weight, 5.62 ± 0.19 g). The results indicated that crabs fed with the KM10 diet had the highest final weight, percent weight gain (PWG), and specific growth rate (SGR) among all treatments (P < 0.05). Crabs fed with the KM0 diet had the lowest activities of total antioxidant capacity (T-AOC), total superoxide dismutase (SOD), glutathione (GSH), and hydroxyl radical scavenging activity and had the highest concentration of malondialdehyde (MDA) in the hemolymph and the hepatopancreas (P < 0.05). In the hepatopancreas, the highest content of 20:5n-3 (EPA) and the lowest content of 22:6n-3 (DHA) were shown in crabs fed with the KM30 diet among all treatments (P < 0.05). With the substitution level of FM with KM gradually increasing from 0% to 30%, the color of the hepatopancreas changed from pale white to red. Expression of tor, akt, s6k1, and s6 in the hepatopancreas was significantly upregulated, while 4e-bp1, eif4e1a, eif4e2, and eif4e3 were downregulated with dietary replacement of FM with KM increasing from 0% to 30% (P < 0.05). Crabs fed with the KM20 diet had notably higher expression of cat, gpx, cMnsod, and prx than those fed with the KM0 diet (P < 0.05). Results demonstrated that 10% replacement of FM with KM can promote growth performance and antioxidant capacity and notably upregulate the mRNA levels of genes related to TOR pathway and antioxidant of swimming crab.

Enhanced removal of fluoride, nitrate, and calcium using self-assembled fungus-flexible fiber composite microspheres combined with microbially induced calcium precipitation

Self-assembled fungus-flexible fiber composite microspheres (SFFMs) were firstly combined with microbially induced calcium precipitation (MICP) in a continuous-flow bioreactor and achieved the efficient removal of fluoride (F^-), nitrate (NO₃^-), and calcium (Ca²⁺). Under the influent F^- of 3.0 mg L^-1, pH of 7.0, and HRT of 8 h, the average removal efficiencies reached 77.54%, 99.39%, and 67.25% (0.29, 2.03, and 8.34 mg L^-1 h^-1), respectively. Fluorescence spectrum and flow cytometry analyses indicated that F^- content significantly affected the metabolism and viability of bacteria. SEM images showed that flexible fibers and intertwined hyphae provided effective locations for bacterial colonization in SFFMs. The precipitated products were characterized by XRD and FTIR, which revealed that F^- was mainly removed in the form of calcium fluoride and calcium fluorophosphate (CaF₂ and Ca₅(PO₄)₃F). High-throughput analysis at different levels demonstrated that Pseudomonas sp. WZ39 acted as the core strain, which played a crucial role in the bioreactor. The mechanism of enhanced denitrification was attributed to minor F^- stress and bioaugmentation technology. This study highlighted the superiorities of SFFMs and MICP combined remediation and documented a promising option for F^-, NO₃^-, and Ca²⁺ removal.

Variation of Water Quality in Ningxia Section of the Yellow River in Recent 5 Years

The Yellow River is very important for human health and social development in China to require good water quality. This study selected the Ningxia section of the Yellow River as the study area to investigate the water quality variation in 2016–2020. A total of 9 water quality parameters were monitored, and 8 parameters including pH, dissolved oxygen, biological oxygen demand, chemical oxygen demand, total phosphate, fluoride, ammonia-nitrogen, and permanganate index were in the range of Class II standard requirement. Dissolved oxygen concentrations ranged from 7.5 to 9.4 mg/L. However, total nitrogen concentrations in 2018–2020 ranged from 1.87 to 2.8 mg/L to cause the pollution. Both the Nemerow index method and the contamination degree method showed that total nitrogen with high concentration exerted the water pollution. Principal component analysis also proved this. Stricter environmental management strategies for controlling total nitrogen should be taken in the future. The findings provided some useful information for water pollution of the Ningxia section of the Yellow River.

Using artificial intelligence to make sustainable development decisions considering VUCA: a systematic literature review and bibliometric analysis

Sustainable development emergent subfields have been rapidly evolving, and their popularity increased in recent years. Sustainable development is a broad concept having numerous sub-concepts including, but not limited to, circular economy, sustainability, renewable energy, green supply chain, reverse logistics, and waste management. This polymorphism makes decision-making in this field to be an abstruse task. In this perplexing circumstance, the presence of VUCA conditions makes decision-making even more challenging. By taking advantage of artificial intelligence tools and approaches, this paper aims to study with a concentration on sustainable development-related decision-making under VUCA phenomena elements using bibliometric and network analyses which can propose numerous novel insights into the most recent research trends in this area by analyzing the most influential and cited research articles, keywords, author collaboration network, institutions, and countries that finally provides results not previously fully comprehended or assessed by other studies on this topic. In this study, an extensive systematic literature review and bibliometric analysis are conducted using 534 research articles out of more than 3600. From the content analysis part, four clusters have been found. The decision parameters, presumptions, and research goal(s) for each model are pointed out too. The findings contribute to both conceptual and practical managerial aspects and provide a powerful roadmap for future research directions in this field, such as how real-life multidimensionality can be considered in sustainable development-related decision-making, or what are the effects of the VUCA in sustainable development considering the circular economy and waste management intersection.

Impaired V-ATPase leads to increased lysosomal pH, results in disrupted lysosomal degradation and autophagic flux blockage, contributes to fluoride-induced developmental neurotoxicity

Fluoride is capable of inducing developmental neurotoxicity, yet its mechanisms remain elusive. We aimed to explore the possible role and mechanism of autophagic flux blockage caused by abnormal lysosomal pH in fluoride-induced developmental neurotoxicity, focusing on the role of V-ATPase in regulating the neuronal lysosomal pH. Using Sprague-Dawley rats exposed to sodium fluoride (NaF) from gestation through delivery until the neonatal offspring reached six months of age as an in vivo model. The results showed that NaF impaired the cognitive abilities of the offspring rats. In addition, NaF reduced V-ATPase expression, diminished lysosomal degradation capacity and blocked autophagic flux, and increased apoptosis in the hippocampus of offspring. Consistently, these results were validated in SH-SY5Y cells incubated with NaF. Moreover, NaF increased the SH-SY5Y lysosomal pH. Mechanistically, V-ATPase B2 overexpression and ATP effectively restored V-ATPase expression, reducing NaF-induced lysosomal alkalinization while increasing lysosomal degradation capacity. Notably, those above pharmacological and molecular interventions diminished NaF-induced apoptosis by restoring autophagic flux. Collectively, the present findings suggested that NaF impairs the lysosomal pH raised by V-ATPase. This leads to reduced lysosomal degradation capacity and triggers autophagic flux blockage and apoptosis, thus contributing to neuronal death. Therefore, V-ATPase might be a promising indicator of developmental fluoride neurotoxicity.

Synergistic removal of fluoride, calcium, and nitrate in a biofilm reactor based on anaerobic microbially induced calcium precipitation

Fluoride (F^-) and calcium (Ca²⁺) are primary causes of skeleton fluorosis and scaling, posing a grievous threat to aquatic lives and public health. Therefore, a novel strategy for polluted groundwater in immobilized biofilm reactor based on the anaerobic microbial induced calcium precipitation (MICP) was proposed, in which loofah was used as a multifunctional strain Cupriavidus sp. W12 growth carrier. Effects of different hydraulic retention time (HRT), initial F^-concentration, and pH on the synchronous removal of pollutants were examined. Under stable operation conditions, the highest efficiencies for Ca²⁺, F^-, and nitrate (NO₃^--N) reached 76.73%, 94.92%, and 100%, respectively. Furthermore, gas chromatography (GC), Fluorescence excitation-emission matrix (EEM), X-ray diffraction (XRD), Scanning electron microscope-energy dispersive spectroscope (SEM-EDS), and Fourier transform infrared spectrometer (FTIR) comprehensively clarified the mechanism of pollutants removal. The results elucidated that the removal of various pollutants was achieved through a combination of anaerobic MICP, adsorption, and co-precipitation. Besides, high-throughput sequencing analysis showed that Cupriavidus had a predominant proportion of 42.36% in the reactor and had stability against pH impact. As the first application of a biofilm reactor based on anaerobic MICP, it put forward a new insight for efficient defluorination and decalcification.

Potential of a novel facultative anaerobic denitrifying Cupriavidus sp. W12 to remove fluoride and calcium through calcium bioprecipitation

This study focused on a novel denitrifying Cupriavidus sp. W12, which can perform microbial induced calcium precipitation (MICP) to remove fluoride (F^-) under aerobic and anaerobic conditions. Under anaerobic condition, the removal ratios of F^-, calcium (Ca²⁺), and nitrate (NO₃^--N) reached 87.52%, 65.03%, and 96.06%, respectively, which were higher than that under aerobic condition (50.17%, 88.21%, and 67.33%, respectively). Higher pH of 8.26 was obtained after 120 h of the strain W12 growth under anaerobic condition than that under aerobic condition (7.77). The F^- removal ratio of 98.20% was predicted by the response surface methodology (RSM). Scanning electron microscopy (SEM) images of anaerobic precipitation were dense and porous. CaCO₃, Ca₅(PO₄)₃OH, Ca₅(PO₄)₃F, and CaF₂ were determined by X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). Self-aggregation of bacteria and adsorption of biological crystal seeds were the determinant of the precipitates formation. The results of infrared spectrometer (FTIR) and excitation-emission matrix (EEM) showed that anaerobic extracellular polymeric substances (EPS) expression led the proportion of hydroxylapatite in the precipitates increased. As the first report on the anaerobic MICP to remove F^-, it provides a theoretical basis for the remediation of F^-, Ca²⁺, and NO₃^--N in groundwater.

Based on G-Series Mouse TH17 Array Study the Effect of Fluoride on C2C12 Cells Cytokines Expression

C2C12 cells were cultured on medium containing fluoride (0, 1, and 2.5 mmol/L) for 48 h to investigate the effect of excessive fluoride on T helper 17 (Th17)-related cytokine expression profile in skeletal muscle cells, and the culture supernatant was collected and subjected for the detection of 18 cytokines via Th17 array. Results showed that compared with the control group, no differential expression proteins (DEPs) were found in the 1 mmol/L fluoride group; however, eight DEPs were upregulated in the 2.5 mmol/L fluoride group, including macrophage inflammatory protein-3α (MIP-3α), interleukin-21 (IL-21), IL-13, IL-17F, IL-28A, transforming growth factor type beta 1 (TGF-β1), IL-23, and IL-17A. In addition, five DEPs (MIP-3α, IL-13, IL-21, TGF-β1, and IL-17F) were upregulated in the 2.5 mmol/L fluoride group compared with the 1 mmol/L fluoride group. Gene ontology analysis revealed that the positive regulation of cytokine production, cytokine activity, receptor ligand activity, and cytokine receptor binding accounted for high percent of DEPs present. Kyoto Encyclopedia of Genes and Genomes analysis showed that these DEPs primarily involved 12 pathways enriched in the cytokine-cytokine receptor interaction and IL-17 signaling pathway after 2.5 mmol/L fluoride treatment. The results indicated that fluoride might induce cytotoxicity by disturbing Th17-related cytokine expression.

Impact of C/N ratio on the fate of simultaneous Ca2+ precipitation, F- removal, and denitrification in quartz sand biofilm reactor

The coexistence of F^-, Ca²⁺, nitrates, and other pollutants in water body has aroused widespread concern. In this research, a novel quartz sand biofilm reactor was established, aiming to study the key factors of different carbon to nitrogen (C/N) ratios (5:1, 4:1, and 3:1), initial Ca²⁺ concentration (180 mg L^-1, 144 mg L^-1, and 108 mg L^-1), and hydraulic retention time (HRT) (4 h, 6 h, and 8 h) on simultaneous Ca²⁺ precipitation, F^- removal, and denitrification. Results showed that the removal efficiencies of Ca²⁺, F^-, and nitrate were 55.04%, 82.64%, and 97.69% under the low C/N ratio of 3:1, initial Ca²⁺ concentration of 180 mg L^-1, and HRT of 8 h. 3-D Excitation-Emission Fluorescence Spectroscopy (3-D EEM) demonstrates that extracellular polymeric substances (EPS) was generated during the growth metabolism. Scanning Electron Microscopy (SEM) and X-ray diffractometer images showed that Ca²⁺, F^- removed in the form of CaCO₃, Ca₅(PO₄)₃F and CaF₂ under Acinetobacter sp. H12 induction. Moreover, high-throughput sequencing results display that the biomineralized bacteria Acinetobacter sp. H12 exerted great influence in the bioreactor. This research will underpin the practical use of multiple pollutants such as F^- and Ca²⁺ wastewater under the different C/N ratios.

Genotoxicity of fluoride subacute exposure in rats and selenium intervention

The aims of this study were to: (i) examine the toxic effects of sodium fluoride (NaF) in blood, liver, spleen, and brain cells of Wistar rats after the subacute exposure; (ii) explore the potential protective properties of selenium (Se) against fluoride toxicity after the simultaneous administration. Twenty male Wistar rats, eight weeks old, weighing approximately 140-190 g, were divided into four experimental groups (n = 5) as follows: I control-tap water; II NaF 150 ppm; III NaF 150 ppm and Se 1.5 mg/L; IV Se 1.5 mg/L, and had available water with solutions ad libitum for 28 days. DNA damage detected by comet assay was confirmed in the liver, spleen, and brain cells, but not in blood. Selenium supplementation together with NaF decreased DNA damage in liver and spleen cells. According to the histological findings, no changes were observed in spleen and brain tissues after NaF administration. Unlike the observed Se protective effect on the DNA level, no significant reduction of liver tissue injury was observed after the NaF and Se treatment, resulting in mild inflammation. Data of this study suggest that DNA damage after NaF subacute exposure at moderately high concentration was reduced in liver and spleen cells due to Se supplementation, but a similar change was not seen in the brain.