Polyethylene glycol-polyvinylidene fluoride/TiO2 nanocomposite polymer coatings with efficient antifouling strategies: Hydrophilized defensive surface and stable capacitive deionization.

Capacitive deionization (CDI) is flourishing as an energy-efficient and cost-effective water desalination method. However, challenges such as electrode degradation and fouling have hindered the practical deployment of CDI technology. To address these challenges, the key point of our strategy is applying a hydrophilic coating composed of polyethylene glycol (PEG)-functionalized nano-TiO2/polyvinylidene fluoride (PVDF) to the electrode interface (labeled as APPT electrode). The PEG/PVDF/TiO2 layer not only mitigates the co-ion depletion, but also imparts the activated carbon (AC) electrode hydrophilicity. As anticipated, the APPT electrode possessed an enhanced desalination capacity of 83.54 µmol g-1 and a low energy consumption of 17.99 Wh m-3 in 10 mM sodium chloride solution compared with the bare AC electrode. Notably, the APPT maintained about 93.19 % of its desalination capacity after 50 consecutive adsorption-desorption cycles in the presence of bovine serum albumin (BSA). During the trial, moreover, no obvious overall performance decline was noted in concentration reduction (Δc), water recovery (WR) and productivity (P) over 50 cycles. This strategy realizes energy-efficient, antifouling and stable brackish water desalination and has great promise for practical applications.

Biochar-immobilized Bacillus megaterium enhances Cd immobilization in soil and promotes Brassica chinensis growth.

Phosphate solubilizing bacteria (PSB) has been considered an environmental-friendly phosphate fertilizer without cadmium (Cd) input into soils, but its possibility of Cd fixation in soil needs to be explored. Since direct inoculation results in a rapid decline of the population and activity, we immobilized Bacillus megaterium with maize straw biochar (B-PSB) and investigated its feasibility in remediating Cd-contaminated soil. Pot experiments showed that the application of B-PSB significantly ameliorated the growth of Brassica chinensis under Cd stress, with a fresh weight increased by 59.08% compared to the Cd-control. B-PSB reduced Cd accumulation in Brassica chinensis by 61.69%, and promoted the uptake of P and N by 134.97% and 98.71% respectively. Microbial community analysis showed B-PSB recruited more plant growth-promoting bacteria in near-rhizosphere soil, which provides a favorable microenvironment for both PSB and crops. Column leaching experiments verified that B-PSB achieved the dissolution of stable P while fixing Cd. Batch tests further revealed that biochar served as a successful carrier facilitating the growth of B. megaterium and Cd immobilization. Given the widespread Cd contamination in agricultural soils, our results indicate that B-PSB is a promising soil amendment to secure food safety.

Developing a Base Editing System for Marine Roseobacter Clade Bacteria.

The Roseobacter clade bacteria are of great significance in marine ecology and biogeochemical cycles, and they are potential microbial chassis for marine synthetic biology due to their versatile metabolic capabilities. Here, we adapted a CRISPR-Cas-based system, base editing, with the combination of nuclease-deactivated Cas9 and deaminase for Roseobacter clade bacteria. Taking the model roseobacter Roseovarius nubinhibens as an example, we achieved precise and efficient genome editing at single-nucleotide resolution without generating double-strand breaks or requesting donor DNAs. Since R. nubinhibens can metabolize aromatic compounds, we interrogated the key genes in the ß-ketoadipate pathway with our base editing system via the introduction of premature STOP codons. The essentiality of these genes was demonstrated, and for the first time, we determined PcaQ as a transcription activator experimentally. This is the first report of CRISPR-Cas-based genome editing in the entire clade of Roseobacter bacteria. We believe that our work provides a paradigm for interrogating marine ecology and biogeochemistry with direct genotype-and-phenotype linkages and potentially opens a new avenue for the synthetic biology of marine Roseobacter bacteria.

Stability and biomineralization of cadmium sulfide nanoparticles biosynthesized by the bacterium Rhodopseudomonas palustris under light.

Cadmium (Cd) pollution is regarded as a potent problem due to its hazard risks to the environment, making it crucial to be removed. Compared to the physicochemical techniques (e.g., adsorption, ion exchange, etc.), bioremediation is a promising alternative technology for Cd removal, due to its cost-effectiveness, and eco-friendliness. Among them, microbial-induced cadmium sulfide mineralization (Bio-CdS NPs) is a process of great significance for environmental protection. In this study, microbial cysteine desulfhydrase coupled with cysteine acted as a strategy for Bio-CdS NPs by Rhodopseudomonas palustris. The synthesis, activity, and stability of Bio-CdS NPs-R. palustris hybrid was explored under different light conditions. Results show that low light (LL) intensity could promote cysteine desulfhydrase activities to accelerate hybrid synthesis, and facilitated bacterial growth by the photo-induced electrons of Bio-CdS NPs. Additionally, the enhanced cysteine desulfhydrase activity effectively alleviated high Cd-stress. However, the hybrid rapidly dissolved under changed environmental factors, including light intensity and oxygen. The factors affecting the dissolution were ranked as follows: darkness/microaerobic ≈ darkness/aerobic < LL/microaerobic < high light (HL)/microaerobic < LL/aerobic < HL/aerobic. The research provides a deeper understanding of Bio-CdS NPs-bacteria hybird synthesis and its stability in Cd-polluted water, allowing advanced bioremediation treatment of heavy metal pollution in water.

Real-World Effectiveness of Primary Series and Booster Doses of Inactivated Coronavirus Disease 2019 Vaccine Against Omicron BA.2 Variant Infection in China: A Retrospective Cohort Study.

BACKGROUND: China has been using inactivated coronavirus disease 2019 (COVID-19) vaccines as primary series and booster doses to protect the population from severe to fatal COVID-19. We evaluated primary and booster vaccine effectiveness (VE) against Omicron BA.2 infection outcomes. METHODS: This was a 13-province retrospective cohort study of quarantined close contacts of BA.2-infected individuals. Outcomes were BA.2 infection, COVID-19 pneumonia or worse, and severe/critical COVID-19. Absolute VE was estimated by comparison with an unvaccinated group. RESULTS: There were 289 427 close contacts ≥3 years old exposed to Omicron BA.2 cases; 31 831 turned nucleic acid amplification test-positive during quarantine, 97.2% with mild or asymptomatic infection, 2.6% with COVID-19 pneumonia, and 0.15% with severe/critical COVID-19. None died. Adjusted VE (aVE) against any infection was 17% for primary series and 22% when boosted. Primary series aVE in adults >18 years was 66% against COVID-19 pneumonia or worse and 91% against severe/critical COVID-19. Booster dose aVE was 74% against pneumonia or worse, and 93% against severe/critical COVID-19. CONCLUSIONS: Inactivated COVID-19 vaccines provided modest protection from infection, very good protection against pneumonia, and excellent protection against severe/critical COVID-19. Booster doses are necessary to provide strongest protection.

Robust self-cleaning membrane with superhydrophilicity and underwater superoleophobicity for oil-in-water separation.

The discharge of oily wastewater has increased dramatically and will bring serious environmental problems. In this work, a self-cleaning and anti-fouling g-C3N4/TiO2/PVDF composite membrane was fabricated via the layer-by-layer approach. The surface of as-prepared composite membrane displayed a superhydrophilic and underwater superoleophobic behavior under irradiation with visible light. Also, upon irradiation with visible light, the fabricated g-C3N4/TiO2/PVDF composite membrane displayed enhanced permeation flux and improved oil removal efficiency as a result of the generation of hydroxyl free radicals during the photocatalytic filtration process. Significantly, irradiation with visible light remarkably improved reusability of the composite membrane by initiating photocatalytic decomposition of deposited oil foulants, which enabled removal of over 99.75% of oils, thus reaching a nearly 100% flux recovery ratio. Furthermore, the g-C3N4/TiO2/PVDF composite membrane exhibited great anti-fouling behavior in photocatalysis-assisted filtration. The mechanistic study revealed that underwater superhydrophobicity and the generation of free hydroxyl radicals jointly contributed to membrane anti-fouling. The greatest advantages of this g-C3N4/TiO2/PVDF composite membrane are that not only does it degrades the oil pollutants, but it also makes the membrane less vulnerable to fouling.

Degradation of Antibiotic Resistance Genes by VADER with CRISPR-Cas Immunity.

The evolution and dissemination of antibiotic resistance genes (ARGs) are prompting severe health and environmental issues. While environmental processes, e.g., biological wastewater treatment, are key barriers to prevent the spread of ARGs, they are often sources of ARGs at the same time, requiring upgraded biotechnology. Here, we present VADER, a synthetic biology system for the degradation of ARGs based on CRISPR-Cas immunity, an archaeal and bacterial immune system for eliminating invading foreign DNAs, to be implemented for wastewater treatment processes. Navigated by programmable guide RNAs, VADER targets and degrades ARGs depending on their DNA sequences, and by employing an artificial conjugation machinery, IncP, it can be delivered via conjugation. The system was evaluated by degrading plasmid-borne ARGs in Escherichia coli and further demonstrated via the elimination of ARGs on the environmentally relevant RP4 plasmid in Pseudomonas aeruginosa. Next, a prototype conjugation reactor at a 10-mL scale was devised, and 100% of the target ARG was eliminated in the transconjugants receiving VADER, giving a proof of principle for the implementation of VADER in bioprocesses. By generating a nexus of synthetic biology and environmental biotechnology, we believe that our work is not only an enterprise for tackling ARG problems but also a potential solution for managing undesired genetic materials in general in the future. IMPORTANCE Antibiotic resistance has been causing severe health problems and has led to millions of deaths in recent years. Environmental processes, especially those of the wastewater treatment sector, are an important barrier to the spread of antibiotic resistance from the pharmaceutical industry, hospitals, or civil sewage. However, they have been identified as a nonnegligible source of antibiotic resistance at the same time, as antibiotic resistance with its main cause, antibiotic resistance genes (ARGs), may accumulate in biological treatment units. Here, we transplanted the CRISPR-Cas system, an immune system via programmable DNA cleavage, to tackle the antibiotic resistance problem raised in wastewater treatment processes, and we propose a new sector specialized in ARG removal with a conjugation reactor to implement the CRISPR-Cas system. Our study provides a new angle for resolving public health issues via the implementation of synthetic biology in environmental contexts at the process level.

Establishing a high-performance anti-fouling PEI-ZIF-PAA membrane with improved Lewis acid-base interactions and hydrophilicity.

Membrane fouling and the trade-off between membrane permeability and selectivity restrict the potential applications of membrane filtration for water treatment. ZIF-8 was found having great permeability and antibiofouling performance, but with issue on particle aggregation makes it difficult to achieve high ZIFs loading and fabricate a defect-free molecular sieving membrane in previous research. In this study, we formed a scalable antibiofouling surface with improved permeability and fouling resistance on a PEI-ZIF-PAA membrane using a layer-by-layer assembly technique. The synergistic effects of being sandwiched between two different polyelectrolyte layers with opposite charges endowed the ZIF nanoparticles with improved stability and scalability for membrane modification. The PEI-ZIF-PAA membrane exhibited a satisfactory water flux of 120.78 LMH, which was 46.97% higher than that of the pristine PES membrane. The normalized water flux loss was serious in the absence of ZIF-8, and the flux increased with the ZIF-8 concentration. Antifouling tests suggested that the PEI-ZIF-PAA membrane possessed good antifouling performance due to the much higher surface hydrophilicity and positive Lewis acid-base interactions with foulants. The HA rejection increased with the ZIF-8 concentration and reached a maximum of 92.1% in the presence of 1.00% (w/v) ZIF-8. The membrane regeneration was tested under physical and chemical cleaning with flux recovery rates of about 85% and 95%. XDLVO analysis showed that the total interaction energy between HA and the PEI-ZIF-8-PAA membrane was 26.45 mJ/m2, and the superior antifouling performance was mainly attributed to Lewis acid-base interactions. This study indicates that ZIF-8 nanocrystals are promising materials for fabricating novel membranes for sewage treatment.

Base editing for reprogramming cyanobacterium Synechococcus elongatus.

Cyanobacteria can directly convert carbon dioxide (CO2) at the atmospheric level to biofuels, value-added chemicals and food products, making them ideal candidates to alleviate global climate change. Despite decades-long pioneering successes, the development of genome-editing tools, especially the CRISPR-Cas-based approaches, seems to lag behind other microbial chassis, slowing down the innovations of cyanobacteria. Here, we adapted and tailored base editing for cyanobacteria based on the CRISPR-Cas system and deamination. We achieved precise and efficient genome editing at a single-nucleotide resolution and demonstrated multiplex base editing in the model cyanobacterium Synechococcus elongatus. By using the base-editing tool, we successfully manipulated the glycogen metabolic pathway via the introduction of premature STOP codons in the relevant genes, building engineered strains with elevated potentials to produce chemicals and food from CO2. We present here the first report of base editing in the phylum of cyanobacteria, and a paradigm for applying CRISPR-Cas systems in bacteria. We believe that our work will accelerate the metabolic engineering and synthetic biology of cyanobacteria and drive more innovations to alleviate global climate change.

Reprogramming Microbial CO2-Metabolizing Chassis With CRISPR-Cas Systems.

Global warming is approaching an alarming level due to the anthropogenic emission of carbon dioxide (CO2). To overcome the challenge, the reliance on fossil fuels needs to be alleviated, and a significant amount of CO2 needs to be sequestrated from the atmosphere. In this endeavor, carbon-neutral and carbon-negative biotechnologies are promising ways. Especially, carbon-negative bioprocesses, based on the microbial CO2-metabolizing chassis, possess unique advantages in fixing CO2 directly for the production of fuels and value-added chemicals. In order to fully uncover the potential of CO2-metabolizing chassis, synthetic biology tools, such as CRISPR-Cas systems, have been developed and applied to engineer these microorganisms, revolutionizing carbon-negative biotechnology. Herein, we review the recent advances in the adaption of CRISPR-Cas systems, including CRISPR-Cas based genome editing and CRISPR interference/activation, in cyanobacteria, acetogens, and methanogens. We also envision future innovations via the implementation of rising CRISPR-Cas systems, such as base editing, prime editing, and transposon-mediated genome editing.

Genome-wide transcriptional regulation in Saccharomyces cerevisiae in response to carbon dioxide.

Sugar metabolism by Saccharomyces cerevisiae produces ample amounts of CO2 under both aerobic and anaerobic conditions. High solubility of CO2 in fermentation media, contributing to enjoyable sensory properties of sparkling wine and beers by S. cerevisiae, might affect yeast metabolism. To elucidate the overlooked effects of CO2 on yeast metabolism, we examined glucose fermentation by S. cerevisiae under CO2 as compared to N2 and O2 limited conditions. While both CO2 and N2 conditions are considered anaerobic, less glycerol and acetate but more ethanol were produced under CO2 condition. Transcriptomic analysis revealed that significantly decreased mRNA levels of GPP1 coding for glycerol-3-phosphate phosphatase in glycerol synthesis explained the reduced glycerol production under CO2 condition. Besides, transcriptional regulations in signal transduction, carbohydrate synthesis, heme synthesis, membrane and cell wall metabolism, and respiration were detected in response to CO2. Interestingly, signal transduction was uniquely regulated under CO2 condition, where upregulated genes (STE3, MSB2, WSC3, STE12, and TEC1) in the signal sensors and transcriptional factors suggested that MAPK signaling pathway plays a critical role in CO2 sensing and CO2-induced metabolisms in yeast. Our study identifies CO2 as an external stimulus for modulating metabolic activities in yeast and a transcriptional effector for diverse applications.

Sonocatalytic degradation of ciprofloxacin using hydrogel beads of TiO2 incorporated biochar and chitosan.

Pharmaceuticals are necessary to be removed from environment. Herein TiO2 incorporated biochar made from pyrolysis of agricultural wastes was encapsulated into chitosan to obtain a novel hydrogel beads. This hydrogel beads executed a dual role as both adsorbent and sonocatalyst, which proved to be suitable for the removal of antibiotic ciprofloxacin (CIP) from water. The results showed that adsorption of CIP followed pseudo first order kinetics model and Langmuir adsorption isotherm model, having maximum adsorption at pH 9. Whereas the degradation was more efficient at pH 6 due to greater standard potential for •OH/H2O in acidic media. The degradation was maximum at 150 W of ultrasonic power, then decreased in presence of dissimilar electrolytes and even reduced to 0 in presence of Na3PO4. Different quenchers such as benzoquinone (BQ), Triethanolamine (TEA) and isopropyl alcohol (IPA) reduced degradation efficiency (DE) and mineralization efficiency (ME). The DE was decreased from 85.23% to 81.50% (BQ), 74.27% (TEA), and 61.77% (IPA) within 25 min. The prepared sonocatalyst was capable of regeneration with DE, remaining sufficiently high (62%) even after four regeneration steps. These results indicate that titanium-biochar/chitosan hydrogel beads (TBCB) are durable and effective for long-term CIP removal.

Transcriptomics and metabolomics of engineered Synechococcus elongatus during photomixotrophic growth.

BACKGROUND: Converting carbon dioxide (CO2) into value-added chemicals using engineered cyanobacteria is a promising strategy to tackle the global warming and energy shortage issues. However, most cyanobacteria are autotrophic and use CO2 as a sole carbon source, which makes it hard to compete with heterotrophic hosts in either growth or productivity. One strategy to overcome this bottleneck is to introduce sugar utilization pathways to enable photomixotrophic growth with CO2 and sugar (e.g., glucose and xylose). Advances in engineering mixotrophic cyanobacteria have been obtained, while a systematic interrogation of these engineered strains is missing. This work aimed to fill the gap at omics level. RESULTS: We first constructed two engineered Synechococcus elongatus YQ2-gal and YQ3-xyl capable of utilizing glucose and xylose, respectively. To investigate the metabolic mechanism, transcriptomic and metabolomic analysis were then performed in the engineered photomixotrophic strains YQ2-gal and YQ3-xyl. Transcriptome and metabolome of wild-type S. elongatus were set as baselines. Increased abundance of metabolites in glycolysis or pentose phosphate pathway indicated that efficient sugar utilization significantly enhanced carbon flux in S. elongatus as expected. However, carbon flux was redirected in strain YQ2-gal as more flowed into fatty acids biosynthesis but less into amino acids. In strain YQ3-xyl, more carbon flux was directed into synthesis of sucrose, glucosamine and acetaldehyde, while less into fatty acids and amino acids. Moreover, photosynthesis and bicarbonate transport could be affected by upregulated genes, while nitrogen transport and assimilation were regulated by less transcript abundance of related genes in strain YQ3-xyl with utilization of xylose. CONCLUSIONS: Our work identified metabolic mechanism in engineered S. elongatus during photomixotrophic growth, where regulations of fatty acids metabolism, photosynthesis, bicarbonate transport, nitrogen assimilation and transport are dependent on different sugar utilization. Since photomixotrophic cyanobacteria is regarded as a promising cell factory for bioproduction, this comprehensive understanding of metabolic mechanism of engineered S. elongatus during photomixotrophic growth would shed light on the engineering of more efficient and controllable bioproduction systems based on this potential chassis.

Chlorine disinfection elevates the toxicity of polystyrene microplastics to human cells by inducing mitochondria-dependent apoptosis.

Microplastics (MPs) are ubiquitous in drinking water and pose potential threats to human health. Despite increasingly attentions on the toxicity of MPs, the deleterious effects of MPs after chlorine disinfection, which might be a more accessible form of MPs, has rarely been considered. Here, we first treated pristine polystyrene microplastics (PS-MPs) with chlorine to simulate the reactions that occur during drinking water treatment, and investigated and compared the cytotoxicity of chlorinated PS-MPs to those of pristine PS-MPs. Chlorine disinfection did not change the size of pristine PS-MPs, but increased the surface roughness. In addition, abundant carbon-chlorine bonds and persistent free radicals were generated on the surface of chlorinated PS-MPs. Compared with pristine PS-MPs, chlorinated PS-MPs markedly inhibited the cell proliferation, changed cellular morphology, destroyed cell membrane integrity, induced cell inflammatory response and apoptosis. Proteomics confirmed the difference in interactions with intracellular proteins between these particles. Furthermore, we found that the regulation of PI3K/AKT and Bcl-2/Bax pathways, oxidative stress-triggered mitochondrial depolarization, and the activation of caspase cascade were identified as the underlying mechanisms for the enhanced apoptosis ratio in GES-1 cells when exposed to chlorinated PS-MPs. This exacerbated cytotoxicity could be explained by the enhanced surface roughness and changed surface chemistry of these PS-MPs after chlorine disinfection. This work discloses the impacts of chlorine disinfection on the cytotoxicity of PS-MPs, which provides new insights for a more systematic risk assessment of MPs.

AOPs enhance the migration of polystyrene nanoparticles in saturated quartz sand.

Wastewater treatment plants are suspected to be significant point sources of microplastic and nanoplastic particles (NPs) in the environment. As one of the main wastewater treatment processes, advanced oxidation processes (AOPs) may change the physicochemical properties of NPs and further affect their migration. However, limited information is known about the environmental fate of NPs after AOP treatment. In this study, polystyrene nanoparticles were treated using two representative AOPs, Fenton and persulfate treatments, and the migration of the NPs in quartz sand was investigated via column transport experiments. FTIR and XPS analysis indicated that a large number of oxygen-containing groups were generated on the NP surface after AOP treatment leading to lower hydrophobicity and a higher negative charge. Besides, the C/O ratio after Fenton and persulfate treatments was increased from 10.98 to 7.25 and 8.68. Moreover, the NPs after AOP treatment exhibited higher mobility in quartz sand in both ultrapure water and 10 mM NaCl solution. It was more obvious in 10 mM NaCl solution with breakthrough percentages of 79.73% for P-PS, 90.97% for F-PS and 95.67% for N-PS, respectively. These results could be explained by the roles of generated oxygen-containing functional groups; first, the higher negative charge enhanced the electrostatic repulsion between treated NPs and sand; second, lower hydrophobicity improved the binding with water molecules in background solution. This work is helpful in understanding the changes of nanoplastics in AOP treatment and their migration in the natural environment, which has far-reaching influence on the environmental fate and behavior of nanoplastics.

Selenium Nanoparticles as an Innovative Selenium Fertilizer Exert Less Disturbance to Soil Microorganisms.

Selenium (Se) is an essential trace element in the human body. Se-enriched agricultural products, obtained by applying Se fertilizer, are important sources of Se supplement. However, Se fertilizer may cause a series of environmental problems. This study investigated the transformation of exogenous selenium nanoparticles (SeNPs) and selenite (SeO3 2-) in soil and explored their effects on soil microbial community and typical microorganisms. SeNPs exhibited a slow-release effect in soil, which promoted the growth of soil microorganisms and enriched soil probiotics. SeO3 2- was converted to a stable and low toxic state in soil, increasing persistent free radicals and decreasing microbial abundance and diversity. The influences of SeNPs and SeO3 2- on two typical soil microorganisms (Bacillus sp. and Escherichia coli) were also evaluated, and SeNPs were more difficult to enter into microorganisms directly, with lower toxicity and higher safety. These results indicated that SeNPs were a more environment-friendly Se additive for agriculture applications. This work provides useful information for better understanding the environmental fate and behavior of Se fertilizer in the soil.

Establishment of a resource recycling strategy by optimizing isobutanol production in engineered cyanobacteria using high salinity stress.

BACKGROUND: Isobutanol is an attractive biofuel with many advantages. Third-generation biorefineries that convert CO2 into bio-based fuels have drawn considerable attention due to their lower feedstock cost and more ecofriendly refining process. Although autotrophic cyanobacteria have been genetically modified for isobutanol biosynthesis, there is a lack of stable and convenient strategies to improve their production. RESULTS: In this study, we first engineered Synechococcus elongatus for isobutanol biosynthesis by introducing five exogenous enzymes, reaching a production titer of 0.126 g/L at day 20. It was then discovered that high salinity stress could result in a whopping fivefold increase in isobutanol production, with a maximal in-flask titer of 0.637 g/L at day 20. Metabolomics analysis revealed that high salinity stress substantially altered the metabolic profiles of the engineered S. elongatus. A major reason for the enhanced isobutanol production is the acceleration of lipid degradation under high salinity stress, which increases NADH. The NADH then participates in the engineered isobutanol-producing pathway. In addition, increased membrane permeability also contributed to the isobutanol production titer. A cultivation system was subsequently developed by mixing synthetic wastewater with seawater to grow the engineered cyanobacteria, reaching a similar isobutanol production titer as cultivation in the medium. CONCLUSIONS: High salinity stress on engineered cyanobacteria is a practical and feasible biotechnology to optimize isobutanol production. This biotechnology provides a cost-effective approach to biofuel production, and simultaneously recycles chemical nutrients from wastewater and seawater.

Cytotoxicity and Effect of Topical Application of Tranexamic Acid on Human Fibroblast in Spine Surgery.

OBJECTIVE: In spinal surgery, considerable blood loss is increasingly treated with the local application of tranexamic acid (TXA). However, little is known about its cytotoxicity and effect on human fibroblasts. This study was to identify the effect of TXA solution on human fibroblast at different concentrations and exposure times in vitro. METHODS: To mimic the actual clinical situation, human fibroblasts were subjected to both limited and chronic exposure to various clinically relevant concentrations of TXA to mimic different ways of topical administration. At time points after treatment, the viability, proliferation, apoptosis, collagen synthesis, adhesion, and migration of fibroblasts were analyzed in vitro. RESULTS: Limited exposure (10 minutes) to a high concentration of TXA (100 mg/mL) did not affect the viability, proliferation, and apoptosis of fibroblasts, and chronic exposure to low concentration of TXA (≤12.5 mg/mL) exerted little effect on viability, proliferation, apoptosis, collagen synthesis, adhesion, and migration of human fibroblasts (P > 0.05). However, the chronic exposure to a high concentration of TXA (≥25 mg/mL) can inhibit the viability, proliferation, collagen synthesis, adhesion and migration, and induce apoptosis of fibroblasts. CONCLUSIONS: Although limited exposure to high concentration of TXA and chronic exposure to low concentration of TXA exerted little effect on fibroblasts, chronic exposure to high concentration of TXA can lead to fibroblast injury.

Selenium nanoparticles ameliorate Brassica napus L. cadmium toxicity by inhibiting the respiratory burst and scavenging reactive oxygen species.

Cadmium (Cd) is a widely distributed soil contaminant which induces oxidative damage and is therefore toxic to plants. Although selenium oxyanions such as selenite (SeO32-) and selenate (SeO42-) can alleviate Cd stress to plants, it is not known whether selenium nanoparticles (SeNPs) are able to do the same. The present study demonstrated the positive impact of both SeNPs and SeO32- on Brassica napus L. growth under conditions of Cd stress. Underlying mechanisms were elucidated using an oxidative stress detection assay, whole-genome RNA sequencing, and RT-qPCR. Application of selenium, especially in the form of SeNPs, decreased Cd-induced reactive oxygen species production by inhibiting the expression of NADPH oxidases (BnaRBOHC, BnaRBOHD1, and BnaRBOHF1) and glycolate oxidase (BnaGLO), thereby decreasing oxidative protein and membrane lipid damage. In addition, SeNPs improved resistance to Cd stress by decreasing Cd accumulation, maintaining intracellular calcium homeostasis, promoting disulfide bond formation, and restoring the waxy outer layer of the leaf surface. Although both forms of selenium decreased Cd toxicity, the beneficial concentration range was more extensive for SeNPs than for SeO32-.