Toxic Chromium Research Articles

Chitosan nanoparticles alleviate chromium toxicity by modulating metabolic homeostasis and promoting chromium sequestration in Zea mays L.

Chitosan nanoparticles (CSNPs) have been proposed as a potential alternative in alleviating chromium (Cr) toxicity. However, the mechanisms underlying remains poorly understood. This study investigates the effects of CSNPs on carbon/nitrogen metabolism, cell wall Cr binding capacity, and antioxidant activity in Zea mays L. under Cr stress. Cr stress decreased the total dry weight (DW) by 48.5 %. By contrast, the total DW was reduced by only 26.2 % in CSNPs-treated plants. Analysis of transcriptomic, enzyme activity, and metabolite content data, CSNPs-treated plants exhibited a higher level of relatively stable Carbon and Nitrogen metabolism than untreated plants. CSNPs application resulted in a substantial increase in the levels of sucrose and soluble protein by 78.0 % and 19.4 % in the leaves, and 60.0 % and 59.7 % in the roots, respectively. Meanwhile, CSNPs increased the contents of glutathione, phytochelatin, and cell wall polysaccharide. This increase resulted in a higher retention of Cr in vacuole and cell wall. Additionally, CSNPs alleviated the oxidative damage by improving antioxidant activity. Overall, our results suggest that CSNPs alleviates Cr toxicity by modulating metabolic homeostasis and promoting Cr sequestration in maize plants. This study provides new insights into the mechanisms underlying CSNPs-mediated Cr stress response with potential implications for crop production.

Performance evaluation on the chemical looping combustion of the chromium-containing leather waste and the fate of chromium using thermodynamic analysis

Leather waste (LW) consistently contains a high content of chromium (Cr), which significantly limits its utilization due to the toxicity of hexavalent chromium formed through oxidation. To prevent this oxidation, chemical looping combustion (CLC) is employed to dispose of the chromium-rich LW. First, the gaseous and solid pollutants generated during air combustion and CLC are compared when LW is used as fuel. The results indicate that CLC is an effective way to significantly decrease the oxidation of chromium (Cr(VI)/Crtotal) at typical operating temperatures. Subsequently, various operating parameters, namely the equivalence ratio of oxygen carrier to leather waste (αOC/LW), the equivalence ratio of steam to leather waste (αS/LW), and air reactor (AR) temperature, are changed to investigate their effects on the CLC combustion and pollutant behaviors. The findings reveal that no chromium is oxidized in the fuel reactor. The oxidation in AR is associated with the presence of Na in the AR, which can react with chromium to form Na2CrO4. Increasing αOC/LW from 0.8 to 1.2 reduces the oxidation of chromium in the AR from 11.68% to 1.76%, while increasing αS/LW from 0.2 to 1.6 has the opposite effect, improving the oxidation of chromium in the AR from 3.16% to 5.18%.

Combined application of earthworms and plant growth promoting rhizobacteria improve metal uptake, photosynthetic efficiency and modulate secondary metabolites levels under chromium metal toxicity in Brassica juncea L

Chromium (Cr) toxicity impairs essential morphological and metabolic activities in plants. The present investigation was carried out to evaluate the beneficial role of plant growth promoting rhizobacterial strains namely Pseudomonas aeruginosa (M1), Burkholderia gladioli (M2) and earthworms (Eisenia fetida) in alleviating Cr toxicity in 10 days old Brassica juncea L. The findings delineated that addition of earthworms and PGPR restored growth, boosted Cr uptake and showed upregulation of metal transporter genes (SULTR 1-4). Supplementation of rhizospheric amendments reinstated Cr induced impairment in photosynthetic attributes. Gaseous exchange attributes, the efficiency of PS II, the content of total phenols, anthocyanin and flavonoids was enhanced with application of earthworms along with PGPR. Confocal imaging of primary photosynthetic pigment (chlorophyll), accessory photosynthetic pigment (carotenoids) and total phenols showed maximum fluorescence with combined inoculation of earthworms and both microbial strains (M1M2). The gene expression analysis revealed that Phyotene synthase (PSY), Photosystem II core protein psb A, psb B were down regulated in Cr stressed seedlings which upon supplementation with earthworms and PGPR were upregulated. Further, Phenylalanine ammonialyase (PAL), chalcone synthase (CHS) were upregulated with addition of earthworms and PGPR. Increased nitric oxide content, enhanced activity and upregulation of nitrate reductase (NR) gene was observed with addition of PGPR and earthworms

Inoculation with multifunctional Bacillus sp. NEAU-DCB1-2 mitigates chromium toxicity in pakchoi (Brassica rapa ssp. chinensis) through a multi-level mechanism

Soil chromium (Cr) accumulation is escalating, severely hindering plant growth and development. Plant growth-promoting bacteria (PGPB) have shown potential in enhancing plant tolerance to heavy metals. However, the role and mechanisms of Cr(VI)-reducing PGPB strains in improving the growth of pakchoi under Cr toxicity remain unclear. This study aimed to isolate a Cr(VI)-reducing PGPB strain from Cr-contaminated soil, evaluate its effect on pakchoi growth under Cr(VI) stress, and investigate the mechanisms involved. Our findings showed that Bacillus sp. NEAU-DCB1-2 effectively reduce Cr(VI) to Cr(III) and produced indole-3-acetic acid and siderophores. Under Cr(VI) stress, inoculation with NEAU-DC1-2 significantly promoted seed germination and early growth of pakchoi. In pot experiments, NEAU-DCB1-2 significantly increased biomass accumulation, plant height, and root length of Cr(VI)-treated pakchoi seedlings, while reducing the Cr(VI) content in root, shoot and soil. Moreover, NEAU-DCB1-2 greatly increased catalase, superoxide dismutase, peroxidase, and ascorbate peroxidase activities in seedlings under Cr(VI) stress, thereby reducing malondialdehyde content. Transcriptome analysis indicated substantial alterations in gene expression patterns after inoculation with NEAU-DCB1-2 under Cr(VI) stress. Further analyses revealed that NEAU-DCB1-2 mainly affected the responses of antioxidant system, metal chelation and transport, together with auxin, abscisic acid, and jasmonic acid signaling to Cr(VI) stress. Conclusively, the Cr(VI)-reducing PGPB strain NEAU-DCB1-2 significantly enhances the growth and Cr tolerance of pakchoi through multiple mechanisms, offering a valuable microbial resource for mitigating the adverse effects of heavy metal contamination in agricultural soils on the yield and safety of vegetable crops.

Toxicity effects of hexavalent chromium on hematological, biochemical and digestive enzyme profiles of Labeo rohita (Hamilton, 1822).

The study provides a descriptive understanding of the toxic effect of heavy metal chromium on the hematological, biochemical, and digestive enzyme profiles in the fingerlings of Labeo rohita. The 96-h LC50 of hexavalent chromium was found to be 15.76 mg/L. Further, the toxicity study was conducted with four different sub-lethal concentrations of 96-h LC50 viz. 1/40th, 1/20th, 1/10th, and 1/5th respectively. The blood samples from the control and treated groups exposed to different concentrations were examined for various physiological parameters. The obtained data showed that, with the increase in sub-lethal concentration, a significant decrease (p < 0.05) in red blood cell (RBCs), hemoglobin (Hb), and hematocrit (Hct) was observed, while total white blood cell (WBCs), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) increased significantly (p < 0.05) in all the treatments. Fishes exposed to chromium for 30 days responded by becoming hyperglycemic, hyperproteineric, and hypoalbuminemia with a gradual rise in concentrations. Alteration in the intestinal digestive enzyme profiles was also observed after 30 days of study. The activity of protease (89.76%), and amylase (41.88%) decreased in the intestine with the highest concentration compared to the control. Conversely, compared to the control, the highest concentration resulted in an increase (146%) in lipase activity. Overall, this study has greatly enhanced our comprehension of the impact of chromium toxicity on various hematological, biochemical, and digestive enzyme parameters in Labeo rohita.

Chromium speciation from tannery wastewater using spectroscopic techniques

The toxicity and reactivity of chromium (Cr) depend on its chemical form or oxidation state which directs the significance of chromium speciation. Cr(VI) is a ‘Class A’ carcinogen whereas Cr(III)) is considered as essential for metabolism. In this work, concentrations of Cr species in different sampling sites of a tannery effluent have been spectroscopically determined. Cr(VI) was determined by UV-visible spectrophotometer through azo dye formation. Total Cr was determined by FAAS while Cr(III) was through subtraction. The Cr(IV) concentration before and after treatment was found in close proximity since the wastewater treatment process was evidently not effective at reducing the level of Cr(IV) in the waste stream (i.e., 3.34 mg/ L versus 3.15 mg/L). The Cr(VI) concentration after treatment (3.15 mg/L) is more than 31 times higher than the permissible limit of WHO (0.1 mg/L). Furthermore, the concentration of Cr(VI) in the downstream of the receiving river (0.59 mg/L) is more than 12 times higher than the upstream (0.046 mg/L) while Cr(III) in the downstream (25.73 mg/L) is more than 50 times higher than the upstream concentration (0.51 mg/L), confirming that the pollution of the river is from the tannery effluent.

Plant-derived biochar and salicylic acid as biostimulants for Lycopersicon esculentum under chromium toxicity conditions: Insights from physiochemical attributes, antioxidants, and relative gene expression

Chromium is a widespread toxic trace metal in cultivated lands owing to human actions, insufficient treatment, and unregulated disposal. Chromium toxicity is facilitated by the production of reactive oxygen species, which induce lipid peroxidation and damage the cellular membranes and nuclei. This study evaluated the preparation and characterization of Pterospermum-derived biochar based on a set of test categories from the International Biochar Initiative. The aim of this study was to assess the effectiveness of Pterospermum-derived biochar and salicylic acid (SA) in promoting the growth and biochemical attributes of tomato plants grown in Cr-contaminated soils. The results showed that Cr toxicity reduced root (42.86 %) and shoot (23.26 %) lengths, which subsequently increased (65 % root and 39.94 % shoot lengths) under SA and biochar treatments. Increased levels of superoxide anions (O2•-) (104.43 %), malondialdehyde (MDA) (115.53 %), and H2O2 (72.35 %) were observed in the Cr-treated tomato plantlets. The combined treatment of SA and biochar effectively reduced MDA, H2O2, and O2•- levels by 51.17 %, 36.89 %, and 45.53 %, respectively, under Cr toxicity conditions. In addition, the combined treatment with SA and biochar enhanced the activity and gene expression of dehydrogenase (7.06-fold), guaiacol peroxidase (6.51-fold), superoxide dismutase (7.90-fold), polyphenol oxidase (1.89-fold), glutathione-s-transferase (2.55-fold), ascorbate peroxidase (1.26-fold), and glutathione peroxidase (8.75-fold) under Cr toxicity conditions. The results highlight the combined treatment of biochar and SA as an effective amendment that offers an environment-friendly method for alleviating Cr toxicity and promoting growth and the antioxidative defense system in tomato plantlets.

Ethylene and hydrogen sulfide regulate hexavalent chromium toxicity in two pulse crops: Implication on growth, photosynthetic activity, oxidative stress and ascorbate glutathione cycle

Sustainable agriculture has become prime importance to feed growing population. To achieve this goal application of exogenous hormones and signaling molecules are gaining important. In this context, we have investigated potential of ethylene (25 μM ethephon; donor) and H2S (10 μM NaHS; donor) in mitigating hexavalent chromium [Cr (VI), 50 μM] toxicity in two pulse seedlings: black bean and mung bean. Cr(VI) declined growth and gas exchange parameters (photosynthetic rate, stomatal conductance, sub cellular CO2 concentration, and transpiration level) which was accompanied by intracellular accumulation of Cr in both pulse crops and the damaging effect was greater in mung bean seedlings. The suppression in the growth and related parameters was occurred due to higher buildup of oxidative stress markers; O2•‾, H2O2, lipid peroxidation (as malondialdehyde, MDA equivalents) and membrane injury in leaf and root of both pulse crops. Cr induced disturbance in AsA-GSH cycle (reduction in the activity of glutathione reductase, ascorbate peroxidase, monodehydroascorbate reductase and dehydroascorbate reductase, and the amount of ASA and GSH) could be one of the reasons for greater accumulation of H2O2. Further, exogenous application of ethylene and H2S significantly ameliorated Cr toxicity on growth and photosynthetic activity by significantly lowering the intracellular Cr accumulation and oxidative biomarkers, and also by strengthening the activity of AsA-GSH cycle. The exogenous application of biosynthesis inhibitors of ethylene (AVG) and H2S (PAG) caused greater damaging effect on these parameters due to more accumulation of Cr(VI), thereby suggesting that the endogenous levels of these regulators are critical for Cr(VI) tolerance. Interestingly, ET did not rescue adverse effects of Cr(VI) in absence of endogenous H2S, while H2S could do so even without endogenous ethylene, suggesting that H2S played downstream signaling to ethylene in regulating Cr(VI) toxicity. Hence, being cheap and easily available theses growth regulators may be considered for sustainable agriculture.

An Overview of Hexavalent Chromium-Induced Necroptosis, Pyroptosis, and Ferroptosis.

Heavy metals are common environmental industrial pollutants. Due to anthropogenic activity, chromium, especially its hexavalent form [Cr(VI)], is a widespread environmental contaminant that poses a threat to human health. In this review paper, we summarize the currently reported molecular mechanisms involved in chromium toxicity with a focus on the induction of pro-inflammatory non-apoptotic cell death pathways such as necroptosis, pyroptosis, and ferroptosis. The review highlights the ability of chromium to induce necroptosis, pyroptosis, and ferroptosis revealing the signaling pathways involved. Cr(VI) can induce RIPK1/RIPK3-dependent necroptosis both in vitro and in vivo. Chromium toxicity is associated with pyroptotic NLRP3 inflammasome/caspase-1/gasdermin D-dependent secretion of IL-1β and IL-18. Furthermore, this review emphasizes the role of redox imbalance and intracellular iron accumulation in Cr(VI)-induced ferroptosis. Of note, the crosstalk between the investigated lethal subroutines in chromium-induced toxicity is primarily mediated by reactive oxygen species (ROS), which are suggested to act as a rheostat determining the cell death pathway in cells exposed to chromium. The current study provides novel insights into the pro-inflammatory effects of chromium, since necroptosis, pyroptosis, and ferroptosis affect inflammation owing to their immunogenic properties linked primarily with damage-associated molecular patterns. Inhibition of these non-apoptotic lethal subroutines can be considered a therapeutic strategy to reduce the toxicity of heavy metals, including chromium.

Sources and health risks of heavy metals in kindergarten dust: The role of particle size

Particle size effects significantly impact the concentration and toxicity of heavy metals (HMs) in dust. Nevertheless, the differences in concentrations, sources, and risks of HMs in dust with different particle sizes are unclear. Therefore, guided by the definition of atmospheric particulate matter, dust samples with particle sizes under 1000 μm (DT1000), 100 μm (DT100), and 63 μm (DT63) from Beijing kindergartens were collected. The concentrations of HMs (e.g., Cd, Pb, Zn, Ni, Cr, Ba, Cu, V, Mn, Co, and Ti) in dust samples with different particle sizes were measured. Besides, the differences in HM concentrations, contamination levels, sources, and source-oriented health risks in dust samples of different particle sizes were systematically explored. The results show that the concentrations of Mn, V, Zn, and Cd gradually increase with decreasing dust particle sizes, the concentrations of Ba and Pb show a decreasing trend, and the concentrations of Cr, Cu, Ni, and Co display an increasing and then decreasing trend. The degree of contamination of HMs in dust of different particle sizes varies, with Cd being the most dominant contaminant. Compared with DT1000 and DT63, DT100 is the most polluted. In addition, the sources of HMs in DT1000, DT100, and DT63 become more single with decreasing particle size, which may be mainly due to the particle-size effect inducing the redistribution of HMs in different sources. Notably, the potential health risk is higher in DT100 than in DT1000 and DT63. The highest contribution of industrial sources to the health risk is found in DT100, which is mainly caused by highly toxic chromium (Cr). This work emphasizes the importance of considering particle size in risk assessment and pollution control, which can provide a theoretical basis for precise management of HMs pollution in dust.

Integrative approach to mitigate chromium toxicity in soil and enhance antioxidant activities in rice (Oryza sativa L.) using magnesium-iron nanocomposite and Staphylococcus aureus strains.

Pollutantsin soil, particularly chromium (Cr), posehigh environmental and health risks due to their persistence, bioavailability, and potential for causing toxicity. Cr impairment in plants act as a deleterious environmental pollutant that enters the food chain and eventually disturbs human health. Current study demonstrated the potential of integrative foliar application of magnesium-iron (Mg +Fe) nanocomposite with Staphylococcus aureus strains to alleviate Cr toxicity in rice (Oryza sativa) crops by improving yield and defense system. Growth and yield traits such as shoot length (15%), root length (17%), shoot fresh weight (14%), shoot dry weight (9%), root fresh weight (23%), root dry weight (7%), number of tillers (33%), number of grains (10%) and spike length (13%) improved by combined application of Mg + Fe (20mgL-1) nanocomposite and S. aureus strains with Cr (110mgkg-1), compared to when applied alone. Mutual Mg + Fe and S. aureus strains application augmented the SPAD value (9%), total chlorophyll (11%), a (12%), b (17%), and carotenoids (32%), with Cr (110mgkg-1), compared to alone. Malondialdehyde (13%), hydrogen peroxide (H2O2) (11%), and electrolyte leakage (7%) were significantly regulated in shoots with combined Mg + Fe and S. aureus strains application with Cr (110mgkg-1) contrasted to alone. Peroxidase (20%), superoxide dismutase (17%), ascorbate peroxidase (18%), and catalase (20%) were increased in shoots with combined Mg + Fe and S. aureus strains application with Cr (110mgkg-1) in comparison to alone. The combined application of Mg + Fe (20mgL-1) nanocomposite and S. aureus strains with Cr (110mgkg-1) enhanced the macro-micronutrients in shoots compared to alone. Cr accumulation in roots (21%), shoots (25%), and grains (47%) were significantly reduced under Cr (110mgkg-1) with combined Mg + Fe and S. aureus strains application, compared to alone. Subsequently, applying combined Mg + Fe and S. aureus strains is a sustainable solution to boost crop production under Cr toxicity.

Exploring the toxicity of chromium on aquatic ecosystems: a comprehensive assessment of growth, physiological responses, genotoxicity, and histological alterations in Etroplus suratensis (Bloch, 1790) juveniles

Exploring the toxicity of chromium on aquatic ecosystems: a comprehensive assessment of growth, physiological responses, genotoxicity, and histological alterations in Etroplus suratensis (Bloch, 1790) juveniles

A Study of Micellar Catalyses on Oxidation of Glycine by QDC in the Presence of Sodium Dodecyl Sulphate (SDS) in Aqueous Perchloric Acid Medium

Aims: To study the micellar effect of SDS on the oxidation of glycine by Quinolinium Dichromate (QDC) in perchloric acid medium. Background: Among the amino acids, glycine plays a major role in multiple metabolic reactions, such as glutathione synthesis and one-carbon metabolism. The oxidation of glycine has received importance because it is the major neurotransmitter inhibitor in the spinal cord and brainstem. In the oxidation process of amino acids, highly toxic chromium (VI) compounds are converted into non-toxic chromium (III) by quinolinium dichromate (QDC) oxidant in an appropriate pH value medium. Objective: 1. To study the catalytic role of anionic surfactant (SDS) on the oxidation of glycine by QDC through micellization, evaluation of critical micelles concentration (CMC) in the presence and absence of glycine and other surface properties along with thermodynamic quantities. 2. Determination of rate constant and order of reaction with respect to QDC, glycine, acid and surfactant which will help to study the kinetics of the reaction 3. Analysis of oxidation product by FT-IR and calculation of activation parameters. 4. Synthesis of oxidant (QDC) and its characterization by UV-Visible spectrophotometer and NMR spectroscopy. Results: First-order kinetics was observed with respect to oxidant, glycine and hydrogen ions. The rate of reaction increased remarkably with an increase in the concentration of surfactant (SDS). The kinetic results show that the ionic strength variation does not have any significant effect on the rate whereas the increase in the dielectric constant of the medium shows a remarkable effect on the rate constant. From stoichiometry study, it was found that 2 moles of oxidant (QDC) consumed 3 moles of glycine to produce aldehyde (Formaldehyde). Conclusion: The observed negative value of (ΔS) entropy of activation and positive (ΔH) enthalpy of activation suggests a more ordered activated complex formation and highly solvated transition state. The kinetics of the reaction in a perchloric acid medium is found to be accelerated in the presence of surfactant (SDS). The kinetics of the reaction follow pseudo first-order decay of Cr(VI) species (QDC), a unity dependence of rate on glycine and perchloric acid. The oxidation product formaldehyde was identified by FTIR. NMR spectrum analysis of synthesized QDC shows a resemblance with pure QDC.

Chromium- and Metal-Reductant-Free Asymmetric Nozaki-Hiyama-Kishi (NHK) Reaction Enabled by Metallaphotoredox Catalysis.

Chiral allylic alcohols are highly prized in synthetic chemistry due to their versatile reactivity stemming from both alkenyl and hydroxyl functionalities. While the Nozaki-Hiyama-Kishi (NHK) reaction is a widely used method for the synthesis of allylic alcohols, it suffers from drawbacks such as the use of toxic chromium salts, high amounts of metal reductants, and poor enantiocontrol. To address these limitations, we present a novel approach involving a metallaphotoredox-catalyzed asymmetric NHK reaction for the production of chiral allylic alcohols. This method marries alkenyl (pseudo)halides with aldehydes, leveraging a synergistic blend of a chiral nickel catalyst and a photocatalyst. This innovative technique enables both oxidative addition and insertion just using nickel, diverging significantly from the conventional NHK reaction pathway mediated by nickel and chromium salts. The adoption of this methodology holds immense promise for crafting a spectrum of intricate compounds, particularly those of significance in pharmaceuticals. Detailed experimental investigations have shed light on the metallaphotoredox process, further enhancing our understanding and enabling further advancements.

Chromium‐ and Metal‐Reductant‐Free Asymmetric Nozaki–Hiyama–Kishi (NHK) Reaction Enabled by Metallaphotoredox Catalysis

AbstractChiral allylic alcohols are highly prized in synthetic chemistry due to their versatile reactivity stemming from both alkenyl and hydroxyl functionalities. While the Nozaki–Hiyama–Kishi (NHK) reaction is a widely used method for the synthesis of allylic alcohols, it suffers from drawbacks such as the use of toxic chromium salts, high amounts of metal reductants, and poor enantiocontrol. To address these limitations, we present a novel approach involving a metallaphotoredox‐catalyzed asymmetric NHK reaction for the production of chiral allylic alcohols. This method marries alkenyl (pseudo)halides with aldehydes, leveraging a synergistic blend of a chiral nickel catalyst and a photocatalyst. This innovative technique enables both oxidative addition and insertion just using nickel, diverging significantly from the conventional NHK reaction pathway mediated by nickel and chromium salts. The adoption of this methodology holds immense promise for crafting a spectrum of intricate compounds, particularly those of significance in pharmaceuticals. Detailed experimental investigations have shed light on the metallaphotoredox process, further enhancing our understanding and enabling further advancements.

Phosphorus and selenium compounding mitigates Cr stress in peanut seedlings by enhancing growth homeostasis and antioxidant properties.

Peanut is an economically important crop, but it is susceptible to Cr contamination. In this study, we used peanut as experimental material to investigate the effects of exogenous P, Se interacting with Cr on the nutrient growth and antioxidant system of peanut seedlings by simulating Cr (0μM, 50μM, and 100μM) stress environment. The results showed that exogenous P, Se supply could mitigate irreversible damage to peanut seedlings by altering the distribution of Cr in roots and aboveground, changing root conformation, and repairing damaged cells to promote growth. When the Cr concentration is 100μM, it exhibits the highest toxicity. Compared to the control group P and Se (0 MM), the treatment with simultaneous addition of P + Se (0.5 + 6.0) resulted in a significant increase in root length and root tip number by 248.7% and 127.4%, respectively. Additionally, there was a 46.9% increase in chlorophyll content, a 190.2% increase in total surface area of the seedlings, and a respective increase of 149.1% and 180.3% in soluble protein content in the shoot and roots. In addition, by restricting the absorption of Cr and reducing the synthesis of superoxide dismutase SOD (Superoxide dismutase), CAT (Catalase), POD (Peroxidase), and MDA (Malonaldehyde), it effectively alleviates the oxidative stress on the antioxidant system. Therefore, the exogenous addition of P (0.5 MM) and Se (6.0 MM) prevented the optimal concentration of chromium toxicity to peanuts. Our research provides strong evidence that the exogenous combination of P and Se reduces the risk of peanut poisoning by Cr, while also exploring the optimal concentration of exogenous P and Se under laboratory conditions, providing a basis for further field experiments.

Co-application of titanium dioxide and hydroxyapatite nanoparticles modulated chromium and salinity stress via modifying physio-biochemical attributes in Solidago canadensis L.

Climate change and human activity have led to an increase in salinity levels and the toxicity of chromium (Cr). One promising approach to modifying these stressors in plants is to use effective nanoparticles (NPs). While titanium dioxide nanoparticles (TiO2 NPs) and hydroxyapatite (HAP NPs) have been demonstrated to increase plant tolerance to abiotic stress by enhancing antioxidant capacity, lipid peroxidation, and secondary metabolites, it is unknown how these two compounds can work together in situations when salt and Cr toxicity are present. The objective of the current study was to determine the effects of foliar-applied TiO2 NPs (15mgL-1) and HAP NPs (250mgL-1) separately and in combination on growth, chlorophyll (Chl), water content, lipid peroxidation, antioxidant capacity, phenolic content, and essential oils (EOs) of Solidago canadensis L. under salinity (100mM NaCl) and Cr toxicity (100mgkg-1 soil). Salinity was more deleterious than Cr by decreasing plant weight, Chl a + b, relative water content (RWC), EO yield, and increasing malondialdehyde (MDA), electrolyte leakage (EL), superoxide dismutase (SOD) activity, and catalase (CAT) activity. The co-application of TiO2 and HAP NPs proved to be more successful. This was evidenced by the increased shoot weight (36%), root weight (29%), Chl a + b (23%), RWC (15%), total phenolic content (TPC, 34%), total flavonoid content (TFC, 28%), and EO yield (56%), but decreased MDA (21%), EL (11%), SOD (22%) and CAT activity (38%) in salt-exposed plants. The study demonstrated the effective strategy of co-applying these NPs to modify abiotic stress by enhancing phenolic compounds and EO yield as key results.

Ultraviolet-enhanced detoxification of chromate and protection of Brassica napus by Aspergillus sojae SH 20

The pervasive issue of heavy metal contamination in agricultural lands poses significant concerns and has wide-ranging implications for ecosystems. However, an encouraging solution lies in exploiting the potential of fungal endophytes to alleviate these detrimental effects. This study emphasized on improving the growth-promoting and chromium-alleviating capabilities of fungal endophytes, particularly Aspergillus sojae strain SH20, through ultraviolet (UV) irradiation. Following UV treatment, SH20 exhibited significantly enhanced growth-promoting and chromium-alleviating capabilities in comparison to its non-irradiated counterpart. Distinctly, the UV-treated SH20 strain demonstrated an improved ability to accumulate and reduce toxic chromate in the soil, effectively addressing the growth constraints imposed by elevated chromium levels in Brassica napus L. The UV-irradiated SH20 variant boosted shoot length up to 3 times that of the control. Similarly, this fungal strain displayed a remarkable increase in the total fresh weight of the seedlings, recording nearly 17 times greater than the control. The isolate treated with UV light reduced the absorption of chromium by about 3 times in the roots, helping the young plants to grow well even when exposed to chromate stress. A drop in root colonization by the UV-treated strain further resulted in reduced chromate absorption by the roots. Also, the strain showed great skill in boosting the host's antioxidant defenses by reducing the buildup of harmful reactive oxygen species (ROS), increasing the removal of ROS, and improving the plant's antioxidant levels, including phenols and flavonoids. When the host plants were exposed to 25 ppm of Cr stress, the UV-irradiated variant SH 20 stimulated the production of flavonoids (246 μg/ml) and phenols (952 μg/ml) in comparison to the control (with 220 μg/ml of flavonoids and 919 μg/ml of phenols). In conclusion, this report highlights how exposing the A. sojae strain SH20 to UV light has the potential to enhance its abilities to promote growth and bioremediate. This suggests a promising solution for addressing heavy metal contamination in agricultural lands.

Green Synthesis of Alzheimer's Disease Probes Aftobetin and Analogues Enabled by Flow Technology and Heterogeneous Photocatalysis.

Aftobetin is a non-invasive diagnosis probe of Alzheimer's disease, that can bind with aggregated β-amyloid peptide in eye's lenses, used for early diagnosis of Alzheimer's disease in a rapid and painless mode. The reported synthesis of this probe fell short in the aspects of greenness and economy due to the involvement of toxic Chromium(IV) oxidant, noble palladium catalyst, elevated reaction temperature, the long reaction time as well as the cumbersome workup. Herein, a holistic optimization of the synthetic process was achieved via the employment of flow technology and heterogenous photocatalysis. Firstly, the integration of heterogenous carbon nitrides photocatalysis and circulation flow technology furnished the air oxidation of alcohol and nickel catalyzed C-N coupling at 20-g scale, thus avoiding the use of toxic Chromium and precious palladium species respectively. Flow-intensified esterification between acyl chloride and alcohol, just taking 30 seconds replaced the Steglich esterification of 6 hours, also avoiding the generation of difficult-to-remove dicyclohexylurea. Finally, C-N coupling, esterification and Knoevenagel condensation were telescoped together, thus simplifying the reaction workup. This fully-flow protocol led to the on-demand synthesis of eight probes.

AQDS-functionalized biochar enhances the bioreduction of Cr(VI) by Shewanella putrefaciens CN32

The bioreduction of toxic chromium(VI) to sparingly soluble chromium(III) represents an environmentally friendly and cost-effective method for remediating Cr contamination. Usually, this bioreduction process is slow and requires the addition of quinone compounds as electron shuttles to enhance the reaction rate. However, the dissolved quinone compounds are susceptible to loss with water flow, thereby limiting their effectiveness. To address this challenge, this study loaded anthraquinone-2,6-disulfonate (AQDS), a typical quinone compound, onto biochar (BC) to create a novel solid-phase electron mediator (BC-AQDS) that can sustainably promote Cr(VI) bioreduction. The experimental results demonstrated that BC-AQDS significantly promoted the bioreduction of Cr(VI), where the reaction rate constant increased by 4.81 times, and the reduction extent increased by 38.31%. X-ray photoelectron spectroscopy and Fourier-Transform Infrared Spectroscopy analysis revealed that AQDS replaced the –OH functional groups on the BC surface to form BC-AQDS. Upon receiving electrons from Shewanella putrefaciens CN32, BC-AQDS was reduced to BC-AH2DS, which subsequently facilitated the reduction of Cr(VI) to Cr(III). This redox cycle between BC-AQDS and BC-AH2DS effectively enhanced the bioreduction rate of Cr(VI). Our study also found that a lower carbonization temperature of BC resulted in a higher surface –OH functional group content, enabling a greater load of AQDS and a more pronounced enhancement effect on the bioreduction of Cr(VI). Additionally, a smaller particle size of BC and a higher dosage of BC-AQDS further contributed to the enhancement of Cr(VI) bioreduction. The preparation of BC-AQDS in this study effectively improve the utilization of quinone compounds and offer a promising approach for enhancing the bioreduction of Cr(VI). It provides a more comprehensive reference for understanding and solving the problem of Cr pollution in groundwater.