Water-responsive supercontractile polymer films for bioelectronic interfaces.

Connecting different electronic devices is usually straightforward because they have paired, standardized interfaces, in which the shapes and sizes match each other perfectly. Tissue-electronics interfaces, however, cannot be standardized, because tissues are soft1-3 and have arbitrary shapes and sizes4-6. Shape-adaptive wrapping and covering around irregularly sized and shaped objects have been achieved using heat-shrink films because they can contract largely and rapidly when heated7. However, these materials are unsuitable for biological applications because they are usually much harder than tissues and contract at temperatures higher than 90 °C (refs. 8,9). Therefore, it is challenging to prepare stimuli-responsive films with large and rapid contractions for which the stimuli and mechanical properties are compatible with vulnerable tissues and electronic integration processes. Here, inspired by spider silk10-12, we designed water-responsive supercontractile polymer films composed of poly(ethylene oxide) and poly(ethylene glycol)-α-cyclodextrin inclusion complex, which are initially dry, flexible and stable under ambient conditions, contract by more than 50% of their original length within seconds (about 30% per second) after wetting and become soft (about 100 kPa) and stretchable (around 600%) hydrogel thin films thereafter. This supercontraction is attributed to the aligned microporous hierarchical structures of the films, which also facilitate electronic integration. We used this film to fabricate shape-adaptive electrode arrays that simplify the implantation procedure through supercontraction and conformally wrap around nerves, muscles and hearts of different sizes when wetted for in vivo nerve stimulation and electrophysiological signal recording. This study demonstrates that this water-responsive material can play an important part in shaping the next-generation tissue-electronics interfaces as well as broadening the biomedical application of shape-adaptive materials.

SARS-CoV-2 NSP12 utilizes various host splicing factors for replication and splicing regulation.

The RNA-dependent RNA polymerase (RdRp) is a crucial element in the replication and transcription of RNA viruses. Although the RdRps of lethal human coronaviruses severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), SARS-CoV, and Middle East respiratory syndrome coronavirus (MERS-CoV) have been extensively studied, the molecular mechanism of the catalytic subunit NSP12, which is involved in pathogenesis, remains unclear. In this study, the biochemical and cell biological results demonstrate the interactions between SARS-CoV-2 NSP12 and seven host proteins, including three splicing factors (SLU7, PPIL3, and AKAP8). The entry efficacy of SARS-CoV-2 considerably decreased when SLU7 or PPIL3 was knocked out, indicating that abnormal splicing of the host genome was responsible for this occurrence. Furthermore, the polymerase activity and stability of SARS-CoV-2 RdRp were affected by the three splicing factors to varying degrees. In addition, NSP12 and its homologues from SARS-CoV and MERS-CoV suppressed the alternative splicing of cellular genes, which were influenced by the three splicing factors. Overall, our research illustrates that SARS-CoV-2 NSP12 can engage with various splicing factors, thereby impacting virus entry, replication, and gene splicing. This not only improves our understanding of how viruses cause diseases but also lays the foundation for the development of antiviral therapies.

A comprehensive study on the co-removal of Cr (VI) and ciprofloxacin via microbial-photocatalytic coupling: Mechanistic insights and performance evaluation.

The increasing contamination of water systems by antibiotics and heavy metals has become a growing concern. The intimately coupled photocatalysis and biodegradation (ICPB) approach offers a promising strategy for the effective removal of mixed pollutants. Despite some prior research on ICPB applications, the mechanism by which ICPB eliminates mixed pollutants remains unclear. In our current study, the ICPB approach achieved approximately 1.53 times the degradation rate of ciprofloxacin (CIP) and roughly 1.82 times the reduction rate of Cr (VI) compared to photocatalysis. Remarkably, after 30 days, the ICPB achieved a 96.1% CIP removal rate, and a 97.8% reduction in Cr (VI). Our investigation utilized three-dimensional fluorescence analysis and photo-electrochemical characterization to unveil the synergistic effects of photocatalysis and biodegradation in removal of CIP and Cr (VI). Incorporation of B-Bi3O4Cl (B-BOC) photocatalyst facilitated electron-hole separation, leading to production of ·O2-, ·OH, and h+ species which interacted with CIP, while electrons reduced Cr (VI). Subsequently, the photocatalytic products were biodegraded by a protective biofilm. Furthermore, we observed that CIP, acting as an electron donor, promoted the reduction of Cr (VI). The microbial communities revealed that the number of bacteria favoring pollutant removal increased during ICPB operation, leading to a significant enhancement in performance.

Influence of meteorological factors on open biomass burning at a background site in Northeast China.

Biomass burning (BB) is a very important emission source that significantly adversely impacts regional air quality. BB produces a large number of primary organic aerosol (POA) and black carbon (BC). Besides, BB also provides many precursors for secondary organic aerosol (SOA) generation. In this work, the ratio of levoglucosan (LG) to organic carbon (OC) and the fire hotspots map was used to identify the open biomass burning (OBB) events, which occurred in two representative episodes, October 13 to November 30, 2020, and April 1 to April 30, 2021. The ratio of organic aerosol (OA) to reconstructed PM2.5 concentration (PM2.5*) increased with the increase of LG/OC. When LG/OC ratio is higher than 0.03, the highest OA/PM2.5* ratio can reach 80%, which means the contribution of OBB to OA is crucial. According to the ratio of LG to K+, LG to mannosan (MN) and the regional characteristics of Longfengshan, it can be determined that the crop residuals are the main fuel. The occurrence of OBB coincides with farmers' preferred choices, i.e., burning biomass in "bright weather". The "bright weather" refers to the meteorological conditions with high temperature, low humidity, and without rain. Meteorological factors indirectly affect regional biomass combustion pollution by influencing farmers' active choices.

Origins of black carbon from anthropogenic emissions and open biomass burning transported to Xishuangbanna, Southwest China.

Black carbon (BC) has importance regarding aerosol composition, radiative balance, and human exposure. This study adopted a backward-trajectory approach to quantify the origins of BC from anthropogenic emissions (BCAn) and open biomass burning (BCBB) transported to Xishuangbanna in 2017. Haze months, between haze and clean months, and clean months in Xishuangbanna were defined according to daily PM2.5 concentrations of >75, 35-75, and <35 µg/m3, respectively. Results showed that the transport efficiency density (TED) of BC transported to Xishuangbanna was controlled by the prevailing winds in different seasons. The yearly contributions to the effective emission intensity of BCAn and BCBB transported to Xishuangbanna were 52% and 48%, respectively. However, when haze occurred in Xishuangbanna, the average BCAn and BCBB contributions were 23% and 77%, respectively. This suggests that open biomass burning (BB) becomes the dominant source in haze months. Myanmar, India, and Laos were the dominant source regions of BC transported to Xishuangbanna during haze months, accounting for 59%, 18%, and 13% of the total, respectively. Furthermore, India was identified as the most important source regions of BCAn transported to Xishuangbanna in haze months, accounting for 14%. The two countries making the greatest contributions to BCBB transported to Xishuangbanna were Myanmar and Laos in haze months, accounting for 55% and 13%, respectively. BC emissions from Xishuangbanna had minimal effects on the results of the present study. It is suggested that open BB in Myanmar and Laos, and anthropogenic emissions in India were responsible for poor air quality in Xishuangbanna.

Combined Mean Corpuscular Hemoglobin, Fibrinogen, and Albumin (MF-A) Is a Novel Prognostic Marker in Patients with Resectable Esophageal Squamous Cell Carcinoma.

BACKGROUND: The aim was to systematically select blood markers routinely tested in clinical settings, which are independently associated with overall survival (OS) and are able to stratify prognosis of esophageal squamous cell carcinoma (ESCC) patients undergoing esophagectomy. METHODS: We selected optimal blood markers for prognostic stratification from 60 candidates in a clinical cohort of 1819 consecutive patients with resectable ESCC in China. Selection was carried out using two-step multivariable Cox proportional hazards regression adjusted for multifaceted confounders. A composite index was developed by multiplying risk factors and dividing them by protective factors. RESULTS: With a median follow-up of 48.07 months, 641 deaths occurred in the 1819 patients and the 5-year OS was 56.30%. Two risk factors (mean corpuscular hemoglobin, fibrinogen) and a protective factor (albumin), all dichotomized and assigned values 1 and 2, were used to construct the composite index marker "MF-A". Three risk groups were created based on the MF-A score including low- (0.5), moderate- (1), and high-risk groups (2 and 4). Compared with patients in the low-risk group (1184/1778, 66.59%), those in the moderate- (488, 27.45%), and high-risk (106, 5.96%) groups were at elevated risk of death (adjusted HR: 1.32, 95% CI: 1.11-1.57; adjusted HR: 2.08, 95% CI: 1.56-2.75; Ptrend < 10-7). Within each TNM stage grouping, OS also trended to be significantly worse as the MF-A score increased. CONCLUSIONS: "MF-A" is a novel independent predictor which may be used to estimate and stratify prognosis for ESCC patients undergoing esophagectomy.

On the fossil and non-fossil fuel sources of carbonaceous aerosol with radiocarbon and AMS-PMF methods during winter hazy days in a rural area of North China plain.

Regional transport is a key source of carbonaceous aerosol in many Chinese megacities including Beijing. The sources of carbonaceous aerosol in urban areas have been studied extensively but are poorly known in upwind rural areas. This work aims to quantify the contributions of fossil and non-fossil fuel emissions to carbonaceous aerosols at a rural site in North China Plain in winter 2016. We integrated online high resolution-time of flight-aerosol mass spectrometer (HR-TOF-AMS) observations and radiocarbon (14C) measurements of fine particles with Positive Matrix Factorization (PMF) analysis as well as Extended Gelencsér (EG) method. We found that fine particle concentration is much higher at the rural site than in Beijing during the campaign (Dec 7, 2016 to Jan 8, 2017). PMF analysis of the AMS data showed that coal-combustion related organic aerosol (CCOA + Oxidized CCOA) and more oxidized oxygenated organic aerosol (MO-OOA) contributed 48% and 30% of organic matter to non-refractory PM1 (NR-PM1) mass. About 2/3 of the OC and EC were from fossil-fuel combustion. The EG method, combining AMS-PMF and 14C data, showed that primary and secondary OC from fossil fuel contribute 35% and 22% to total carbon (TC), coal combustion emission dominates the fossil fuel sources, and biomass burning accounted for 21% of carbonaceous aerosol. In summary, our results confirm that fossil fuel combustion was the dominant source of carbonaceous aerosol during heavy pollution events in the rural areas. Significant emissions of solid fuel carbonaceous aerosols at rural areas can affect air quality in downwind cities such as Beijing and Tianjin, highlighting the benefits of energy transition from solid fuels to cleaner energy in rural areas.

Primary nature of brown carbon absorption in a frigid atmosphere with strong haze chemistry.

Severe haze hovered over Harbin during the heating season of 2019-2020, making it one of the ten most polluted Chinese cities in January of 2020. Here we focused on the optical properties and sources of brown carbon (BrC) during the extreme atmospheric pollution periods. Enhanced formation of secondary BrC (BrCsec) was evident as relative humidity (RH) became higher, accompanied with a decrease of ozone but concurrent increases of aerosol water content and secondary inorganic aerosols. These features were generally similar to the characteristics of haze chemistry observed during winter haze events in the North China Plain, and indicated that heterogeneous reactions involving aerosol water might be at play in the formation of BrCsec, despite the low temperatures in Harbin. Although BrCsec accounted for a substantial fraction of brown carbon mass, its contribution to BrC absorption was much smaller (6 vs. 28%), pointing to a lower mass absorption efficiency (MAE) of BrCsec compared to primary BrC. In addition, emissions of biomass burning BrC (BrCBB) were inferred to increase with increasing RH, coinciding with a large drop of temperature. Since both the less absorbing BrCsec and the more absorbing BrCBB increased as RH became higher, the MAE of total BrC were largely unchanged throughout the measurement period. This study unfolded the contrast in the source apportionment results of BrC mass and absorption, and could have implications for the simulation of radiative forcing by brown carbon.

Effects of oocyte vitrification on gene expression in the liver and kidney tissues of adult offspring.

Oocyte vitrification is an important assisted reproductive technology (ART) that preserves the fertility of unmarried patients with malignant tumors, and promotes the development of the oocyte donation program. In recent years, the effects of ART, including the vitrification of oocytes and embryos on the health of offspring, have attracted much attention; however, it is difficult to conduct long-term follow-up and biochemical evaluation in humans. In this study, we detected the effect of oocyte vitrification on gene expression in the organs of adult mice offspring by RNA sequencing for the first time. Our results showed that only a small amount of gene expression was significantly affected. Seven genes (Tpm3, Hspe1-rs1, Ntrk2, Cyp4a31, Asic5, Cyp4a14, Retsat) were abnormally expressed in the liver, and ten genes (Lbp, Hspe1-rs1, Prxl2b, Pfn3, Gm9008, Bglap3, Col8a1, Hmgcr, Ero1lb, Ifi44l) were abnormal in the kidney. Several genes were related to metabolism and disease occurrence in the liver or kidney. Besides, we paid special attention to the expression of known imprinted genes and DNA methylation-related genes in adult organs, which are susceptible to oocyte cryopreservation in the preimplantation stage. As a result, some of these transcripts were detected in adult organs, but they were not affected by oocyte vitrification. In conclusion, we first report that oocyte vitrification did not significantly change the global gene expression in offspring organs; nonetheless, it can still influence the transcription of a few functional genes. The potential adverse effects caused by oocyte vitrification need attention and further study.

Recovery of Acid and Alkaline from Industrial Saline Wastewater by Bipolar Membrane Electrodialysis under High-Chemical Oxygen Demand Concentration.

Actual high saline wastewater containing concentrated organics and sodium chloride is a bioenergy and renewable resource. This study compared two different bipolar membrane electrodialysis membranes from two companies' stacks to recover HCl and NaOH from sodium chloride solution and actual chemical wastewater. The results demonstrated that the electrolysis rates were around 1.5 kg/m2h, the HCl and NaOH production rates were about 0.9 kg/m2h, energy consumption was in the range of 1.05-1.27 kWh/kg, and the economic benefits were above 1 yuan/h in BMED systems. From analyzing the performance of seven different BMED membrane stacks, the B2 stack was chosen for electrolyzing actual high salt wastewater to observe the effect of chemical oxygen demand on BMED systems, where electrolytic salt performance, HCl-NaOH alkali production rates, and energy consumption show linear dependence on time for 5000 mg/L chemical oxygen demand wastewater. It illustrated chemical oxygen demand can enhance energy consumption and reduce electrolytic salt performance and the acid and alkali production rates, due to improving the membrane area resistance. In this study, the effect of high COD saline wastewater on the performance of a BMED membrane stack was clarified and the mechanism was analyzed for its practical application in treating chemical high salt wastewater.

Optimized preparation of activated carbon from furfural residue using response surface methodology and its application for bisphenol S adsorption.

Furfural residue (FR), a solid waste, was applied as the precursor to prepare activated carbon by steam activation. The Box-Behnken design (BBD) approach-based response surface methodology (RSM) was utilized to optimize the preparation conditions to evaluate their effects on the performance of activated carbon from furfural residue (FRAC). The optimum preparation conditions of FRAC were found as follows: activation temperature of 922 °C, activation time of 62 min, and the mass ratio of char to H2O of 1:4.5, resulting in 1,501.84 mg/g of iodine adsorption capacity and 1,662.41 m2/g of specific surface area. The FRAC was characterized and then the adsorption performance of bisphenol S (BPS) on FRAC was investigated. Langmuir and Koble-Corrigan isotherm models were well fitted to the experimental data, and the adsorption kinetics process was perfectly described by the pseudo-second-order model. Thermodynamic parameters showed that the adsorption of BPS was a spontaneous exothermic process. Besides, the regeneration efficiency of FRAC was over 97% after five consecutive cycles. The maximum monolayer adsorption capacity of FRAC for BPS was 3.2848 mmol/g at 298 K, indicating that the FRAC was an excellent adsorbent for the removal of BPS from aqueous solutions.

[Association of miR-146a rs2910164 G/C polymorphism with its abnormal expression and risk of gastric cancer].

OBJECTIVE: To assess the influence of rs2910164 G/C single nucleotide polymorphism (SNP) of the miR-146a gene on its expression and susceptibility to gastric cancer. METHODS: Fifty three gastric cancer patients and six gastric cancer cell lines were selected for determining the miR-146a expression by Taqman quantitative PCR. A model was constructed to assess the influence of miR-146a overexpression on the growth of AGS gastric cancer cells. A case-control study involving 417 gastric cancer patients and 420 cancer-free individuals was then conducted, and the allelic and genotypic frequencies of the rs2910164 G/C SNP were compared. The genotypes of all subjects were determined by using a Taqman allelic discrimination assay. A Taqman assay was also used to quantify mature and pri-miR-146a transcripts among 65 gastric cancer patients with known genotypes. RESULTS: The expression of miR-146a was down-regulated among the 53 gastric cancer patients and six gastric cancer cell lines. Over-expression of miR-146a has suppressed the growth of gastric cancer by inhibiting the G1/S-phase transition of AGS cells. The case-control study showed that subjects with GC/CC genotypes had significantly lower risk for gastric cancer compared with those with GG genotype. In addition, miR-146a G/C SNP has significantly increased the level of mature miR-146a in those with GC/CC genotype compared with GG genotype. CONCLUSION: Down-regulation of miR-146a may play an important role in the pathogenesis of gastric cancer. The rs2910164 polymorphism of the miR-146a gene may reduce the risk of gastric cancer by influencing the processing of mature miR-146a.

Efficient Conversion of NO to NO2 on SO2-Aged MgO under Atmospheric Conditions.

The NO-NO2 cycle determines the formation of O3 and hence plays a critical role in the oxidizing capacity of troposphere. Traditional view concluded that the heterogeneous oxidation of NO to NO2 was negligible due to the weak reactivity of NO on aerosols, compared to the homogeneous oxidation process. However, the results here reported for the first time that SO2 can greatly promote the heterogeneous transformation of NO into NO2 and HONO on MgO particles under ambient conditions. The uptake coefficients of NO were increased by 2-3 orders of magnitudes on SO2-aged MgO, compared to the fresh sample. Based on spectroscopic characterization and density functional theory (DFT) calculations, the active sites for the adsorption and oxidation of NO were determined to be sulfates, where an intermediate [SO4-NO] complex was formed during the adsorption. The decomposition of this species led to the formation of NO2 and the change of sulfate configuration. The formed NO2 could further react with surface sulfite to form HONO and sulfate. The conversion of NO to NO2 and HONO on the SO2-aged MgO surface under ambient conditions contributes a new formation pathway of NO2 and HONO and could be quite helpful for understanding the source of atmospheric oxidizing capacity as well as the formation of air pollution complexes in polluted regions such as the northern China.

Dust-Dominated Coarse Particles as a Medium for Rapid Secondary Organic and Inorganic Aerosol Formation in Highly Polluted Air.

Secondary aerosol (SA) frequently drives severe haze formation on the North China Plain. However, previous studies mostly focused on submicron SA formation, thus our understanding of SA formation on supermicron particles remains poor. In this study, PM2.5 chemical composition and PM10 number size distribution measurements revealed that the SA formation occurred in very distinct size ranges. In particular, SA formation on dust-dominated supermicron particles was surprisingly high and increased with relative humidity (RH). SA formed on supermicron aerosols reached comparable levels with that on submicron particles during evolutionary stages of haze episodes. These results suggested that dust particles served as a medium for rapid secondary organic and inorganic aerosol formation under favorable photochemical and RH conditions in a highly polluted environment. Further analysis indicated that SA formation pathways differed among distinct size ranges. Overall, our study highlights the importance of dust in SA formation during non-dust storm periods and the urgent need to perform size-resolved aerosol chemical and physical property measurements in future SA formation investigations that are extended to the coarse mode because the large amount of SA formed thereon might have significant impacts on ice nucleation, radiative forcing, and human health.

Exosomes derived from human umbilical cord mesenchymal stem cells repair injured endometrial epithelial cells.

PURPOSE: To investigate whether exosomes derived from human umbilical cord mesenchymal stem cells (hucMSC-derived exosomes) can repair injured endometrial epithelial cells (EECs). METHODS: HucMSC-derived exosomes and mouse primary EECs were isolated and purified. EECs were exposed to oxygen and glucose deprivation for 2 h followed by reoxygenation to mimic injury. After oxygen and glucose deprivation/reoxygenation (OGD/R), hucMSC-derived exosomes were added to the EEC culture medium. After 24 h of co-treatment, cell viability and cell death were tested by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay and lactate dehydrogenase (LDH) assay, respectively. The expression of proinflammatory cytokines was tested by real-time PCR, enzyme-linked immunosorbent assay (ELISA), and Western blot to investigate the potential mechanism. RESULTS: Compared with the control group, 5, 10, and 15 µg/mL of hucMSC-derived exosomes significantly attenuated cell viability decrease and inhibited LDH release of injured EECs, but 1 µg/mL of hucMSC-derived exosomes had no effect on either cell viability or LDH release. Real-time PCR and ELISA analysis revealed that 10 µg/mL of hucMSC-derived exosomes significantly inhibited the release of interleukin-6 (IL-6) and interleukin-1 beta (IL-1ß) and increased tumor necrosis factor alpha (TNFA) in injured EECs. In addition, 10 µg/mL of hucMSC-derived exosomes significantly inhibited toll-like receptor 4 (TLR4) and v-rel reticuloendotheliosis viral oncogene homolog A (RelA) expression in injured EECs. CONCLUSIONS: In OGD/R-induced injured EECs, hucMSC-derived exosomes efficiently improved the cell viability, reduced cell death, and exhibited anti-inflammatory properties against OGD/R.

A transposition-active Phyllostachys edulis long terminal repeat (LTR) retrotransposon.

Due to infrequent sexual reproduction, moso bamboo breeding by hybridization is extremely technically difficult. Insertional mutagenesis based on endogenous active transposons may thus serve as an alternative method to create new germplasm of moso bamboo. In the present study, using LTR-STRUC, a full-length intact long terminal repeat (LTR) retrotransposon was identified in the moso bamboo genome and was named PHRE2 (Phyllostachys edulis retrotransposon 2). The 5' and 3' LTR sequences of PHRE2 were highly (98.39%) similar. PHRE2 contains all domains necessary for transposition such as gag, pr, rt, rh, and int. The coding frames of these essential domains were complete and had no apparent mutations. In addition, PHRE2 possessed a prime binding site (PBS), a polypurine tract (PPT), and two typical sequences of LTR retrotransposons. A genome-wide scan showed that the moso bamboo genome has only one full-length sequence of PHYRE2. After its transfer to Arabidopsis thaliana, an increase in PHRE2 copy number occurred in the T3 plants compared to in the T2 plants. After moso bamboo seedlings were grown in tissue culture or treated by irradiation or plant hormones, the copy number of PHRE2 significantly increased. These findings indicate that PHRE2 has the capacity for transposition, which can be induced by environmental conditions.

Electrochemiluminescence based detection of microRNA by applying an amplification strategy and Hg(II)-triggered disassembly of a metal organic frameworks functionalized with ruthenium(II)tris(bipyridine).

An electrochemiluminescence (ECL) biosensor is described for the detection of microRNA (miRNA-155) based on tris(bipyridine)ruthenium(II) functionalized metal organic framework (RuMOF) materials. The material was prepared by a solvothermal method and was found to be stable even in acidic solution. However, it is selectively and sensitively disassembled by Hg(II) ions, resulting in the release of large quantities of Ru(II)(bpy)3 ions, which produces a strong ECL signal. In view of the ion-selective disassembly and release and strand displacement process, an ultrasensitive ECL sensing method was established for detection of microRNAs. In the presence of the target, the hairpin structure of H1 can open and hybridize with the hairpin probe H2 to form a more stable H1-H2 duplex structure than the H1-target hybrid. The target of hybridization to H1 was immediately freed from the structure and the released target re-entered the new hairpin assembly target recovery process. The remaining H2 single fragment can bind to the I-RuMOFs-conjugates. The more hairpin probes H1, the more I-RuMOFs-conjugates load the DNA fragments, leading to the signal amplification. The method works in the 0.8 f. to 1.0 nM miRNA-155 concentration range and has a detection limit of 0.3 fM. The assay is sensitive, fairly specific and remarkably stable. In our perception, it offers an attractive tool for the sensitive detection of microRNAs in clinical samples. Graphical abstract An electrochemiluminescence (ECL) based biosensor is described for the detection of microRNA (miRNA-155) based on the use of a metal organic framework functionalized with ruthenium(II)tris(bipyridine) that was deposited on a glassy carbon electrode (GCE) modified with gold nanoparticles.

Pretreatment with NaCl Promotes the Seed Germination of White Clover by Affecting Endogenous Phytohormones, Metabolic Regulation, and Dehydrin-Encoded Genes Expression under Water Stress.

This study was designed to examine the effects of NaCl pretreatment on the seed germination of white clover (Trifolium repens cv. Ladino) under water stress induced by 19% polyethylene glycol (PEG) 6000. Lower concentrations of NaCl (0.5, 1, and 2.5 mM) pretreatment significantly alleviated stress-induced decreases in germination percentage, germination vigor, germination index, and radicle length of seedlings after seven days of germination under water stress. The soaking with 1 mM of NaCl exhibited most the pronounced effects on improving seed germination and alleviating stress damage. NaCl-induced seeds germination and growth could be associated with the increases in endogenous gibberellic acid (GA) and indole-3-acetic acid (IAA) levels through activating amylases leading to improved amylolysis under water stress. Seedlings pretreated with NaCl had a significantly lower osmotic potential than untreated seedlings during seed germination, which could be related to significantly higher soluble sugars and free proline content in NaCl-treated seedlings under water stress. For antioxidant metabolism, NaCl pretreatment mainly improved superoxide dismutase, peroxidase, ascorbate peroxidase, and glutathione reductase activities, transcript levels of FeSOD, APX, and DHAR, and the content of ascorbic acid, reduced glutathione, and oxidized glutathione during seed germination under water stress. The results indicated that seeds soaking with NaCl could remarkably enhance antioxidant metabolism, thereby decreasing the accumulation of reactive oxygen species and membrane lipid peroxidation during germination under water stress. In addition, NaCl-upregulated dehydrin-encoded genes SK2 expression could be another important mechanism of drought tolerance during seeds germination of white clover in response to water stress.

The γ-Aminobutyric Acid (GABA) Alleviates Salt Stress Damage during Seeds Germination of White Clover Associated with Na⁺/K⁺ Transportation, Dehydrins Accumulation, and Stress-Related Genes Expression in White Clover.

The objective of this study was to determine the effect of soaking with γ-aminobutyric acid (GABA) on white clover (Trifolium repens cv. Haifa) seed germination under salt stress induced by 100 mM NaCl. Seeds soaking with GABA (1 µM) significantly alleviated salt-induced decreases in endogenous GABA content, germination percentage, germination vigor, germination index, shoot and root length, fresh and dry weight, and root activity of seedling during seven days of germination. Exogenous application of GABA accelerated starch catabolism via the activation of amylase and also significantly reduced water-soluble carbohydrate, free amino acid, and free proline content in seedlings under salt stress. In addition, improved antioxidant enzyme activities (SOD, GPOX, CAT, APX, DHAR, GR and MDHR) and gene transcript levels (Cu/ZnSOD, FeSOD, MnSOD, CAT, GPOX, APX, MDHR, GPX and GST) was induced by seeds soaking with GABA, followed by decreases in O2∙-, H2O2, and MDA accumulation during germination under salt stress. Seeds soaking with GABA could also significantly improve Na⁺/K⁺ content and transcript levels of genes encoding Na⁺/K⁺ transportation (HKT1, HKT8, HAL2, H⁺-ATPase and SOS1) in seedlings of white clover. Moreover, exogenous GABA significantly induced the accumulation of dehydrins and expression of genes encoding dehydrins (SK2, Y2K, Y2SK, and dehydrin b) in seedlings under salt stress. These results indicate that GABA mitigates the salt damage during seeds germination through enhancing starch catabolism and the utilization of sugar and amino acids for the maintenance of growth, improving the antioxidant defense for the alleviation of oxidative damage, increasing Na⁺/K⁺ transportation for the osmotic adjustment, and promoting dehydrins accumulation for antioxidant and osmotic adjustment under salt stress.

Metal-Enhanced Ratiometric Fluorescence/Naked Eye Bimodal Biosensor for Lead Ions Analysis with Bifunctional Nanocomposite Probes.

A novel metal-enhanced ratiometric fluorescence/naked eye bimodal biosensor based on ZnFe2O4@Au-Ag bifunctional nanocomposite and DNA/CeO2 complex for lead ions (Pb2+) has been successfully developed. The nanocomposite probe was composed of a magnetic ZnFe2O4 core and a Au-Ag hollow nanocube shell. Upon bioconjugation, bifunctional magnetic nanocomposites could not only make the probe possess excellent recyclability but also provide an enrichment of "hot spots" for surface enhanced fluorescence detection of Pb2+ by a metal-enhanced fluorescence effect. Typically, the bifunctional nanocomposites conjugated with double-stranded DNA (included Pb2+-specific DNAzyme strand and corresponding substrate strand) to form a Pb2+ biosensor. Nanoceria as a fluorescence quencher strongly adsorbed DNA. Therefore, the formation of double-stranded DNA brought the labeled nitrogen sulfur doped carbon dots (N,S-CDs) and CeO2 into close proximity, which significantly quenched the fluorescence of N,S-CDs. The presence of Pb2+ led to the breakage of the DNAzyme strand, resulting in the fluorescence signal of Cy3 decreasing, while the fluorescence intensity of N,S-CDs aggrandized. First, a preliminary test of Pb2+ was performed by the naked eye. The disengaged DNA/CeO2 complex could result in color change after adding H2O2 because of autocatalysis of CeO2, resulting in real-time visual detection of Pb2+. If further accurate determination was required, the fluorescence intensity ratio of these two fluorescence indicators was measured at 562 and 424 nm (I562/I424). A good linear correlation exists between the log(I562/I424) and the logarithm of Pb2+ concentrations ranging from 10-12 to 3 × 10-6 M. Remarkably, the detection limit of this ratiometric biosensor was 3 × 10-13 M, which ascribed to its superior fluorescence enhancement. Interestingly, the developed bifunctional nanocomposite probe manifests good recyclability and selectivity. More importantly, the biosensor provided potential application of on-site and real-time unknown Pb2+ ions in real systems.