Bifunctional MOF-Encapsulated Cobalt-Doped Carbon Dots Nanozyme-Powered Chemiluminescence/Fluorescence Dual-Mode Detection of Aflatoxin B1.

A novel bifunctional MOF-encapsulated cobalt-doped carbon dots nanozyme (Co-CD/PMOF) with excellent peroxidase-mimic catalytic activity and fluorescence property was synthesized and employed to fabricate a chemiluminescence/fluorescence (CL/FL) dual-mode immunosensor for AFB1 detection. Co-CD/PMOF could catalyze the luminol/H2O2 system to generate robust and long-lasting CL signals due to the slow diffusion effect and continuous generation of •OH, O2•-, and 1O2 species. Differing from traditional flash-type CL emissions, this glow-type CL emission is helpful to fabricate a sensitive and accurate CL sensing platform. Then the CL/FL dual-mode detection of AFB1 was developed using antibody-functionalized Co-CD/PMOF as the signal-amplifying nanoprobe. The CL mode assay based on indirect competitive immune principle was carried out on a chemiluminescence optical fiber platform, where the AFB1-OVA-functionalized optical fiber probe was employed for biorecognition, separation, and signal conducting. The AFB1 detection range and LOD were 0.63-69.36 ng/mL and 0.217 ng/mL, respectively. Using AFB1 antibody-functionalized immunomagnetic beads for capturing and separation, the FL mode detection of AFB1 was established based on the sandwich immune principle. A linear range of 0.54-51.91 ng/mL and a LOD of 0.027 ng/mL were obtained. This work designed a sensitive, rapid, and reliable nanozyme-powered dual-mode assay strategy and provided technical support in the field of environmental monitoring and food safety.

Release mechanism and interactions of cadmium and arsenic co-contaminated ferrihydrite by simulated in-vitro digestion assays.

Cadmium (Cd) and arsenic (As) co-contamination is widespread and threatens human health, therefore it is important to investigate the bioavailability of Cd and As co-exposure. Currently, the interactions of Cd and As by in vitro assays are unknown. In this work, we studied the concurrent Cd-As release behaviors and interactions with in vitro simulated gastric bio-fluid assays. The studies demonstrated that As bioaccessibility (2.04 to 0.18 ± 0.03%) decreased with Cd addition compared to the As(V) single system, while Cd bioaccessibility (11.02 to 39.08 ± 1.91%) increased with As addition compared to the Cd single system. Release of Cd and As is coupled to proton-promoted and reductive dissolution of ferrihydrite. The As(V) is released and reduced to As(Ⅲ) by pepsin. Pepsin formed soluble complexes with Cd and As. X-ray photoelectron spectroscopy showed that Cd and As formed Fe-As-Cd ternary complexes on ferrihydrite surfaces. The coordination intensity of As-O-Cd is lower than that of As-O-Fe, resulting in more Cd release from Fe-As-Cd ternary complexes. Our study deepens the understanding of health risks from Cd and As interactions during environmental co-exposure of multiple metal(loid)s.

Detection of SARS-CoV-2 S protein based on FRET between carbon quantum dots and gold nanoparticles.

The COVID-19 pandemic caused by SARS-CoV-2 virus brings nasty crisis for public health in the world. Until now, the virus has caused multiple infections in many people. Detecting antigen to SARS-CoV-2 is a powerful method for the diagnosis of COVID-19 and is helpful for controlling and stopping the pandemic. Herein, a rapid and quantitative detection method of SARS-CoV-2 spike(S) protein was built based on the fluorescence resonance energy transfer (FRET) phenomenon without complicated steps. In the process of detecting, the carbon quantum dots (CQDs) and gold nanoparticles (AuNPs) act as donor and acceptor. By modifying the SARS-CoV-2 antibodies on the surface of CQDs and AuNPs, we achieved S protein specific detection using the distance-based FRET phenomenon. Through the electric charge regulation, the limit of detection (LOD) is 0.05 ng/mL, the linear range is 0.1-100 ng/mL, and the detection process only takes 12 min. The proposed method exhibits several advantages such as be available for variants (B.1.1.529 and B.1.617.2) and be suitable for human serum, which is of significance for detecting viral in time and prevention the viral transmission.

Rational design of three-in-one Pt/MnO2/GO hybrid nanozyme with enhanced catalytic performance for colorimetric detection of ascorbic acid and cysteine.

In this work, a novel three-in-one Pt/MnO2/GO hybrid nanozyme with wide pH and temperature working range was rational prepared using simple hydrothermal and reduction strategy. The prepared Pt/MnO2/GO displayed enhanced catalytic activity than single active component due to the excellent conductivity of GO, the increased active sites, the increased electron transfer capacity, the synergistic effect between each component and the decreased binding energy for adsorbed intermediates. Combing chemical characterization and theoretical simulation calculations, the O2 reduction process on the Pt/MnO2/GO nanozymes and the generated reactive oxygen species in the nanozyme-TMB system were thoroughly illustrated. Based on the excellent catalytic activity of Pt/MnO2/GO nanozymes, a colorimetric strategy was proposed to detect the ascorbic acid (AA) and cysteine (Cys), and the experimental results indicated that detection range of AA was 0.35-56 µM with a LOD of 0.075 µM and detection range of Cys was 0.5-32 µM with a LOD of 0.12 µM. Good recoveries were achieved in the human serum and fresh fruit juice detection procedures, demonstrating the potential applications of Pt/MnO2/GO-based colorimetric strategy in complex biological and food samples.

Microgravity stress alters bacterial community assembly and co-occurrence networks during wheat seed germination.

Bacterial interactions occurring on and around seeds are integral to plant fitness, health and productivity. Although seed- and plant-associated bacteria are sensitive to environmental stress, the effects of microgravity, as present during plant cultivation in space, on microbial assembly during seed germination are not clear. Here, we characterized the bacterial microbiome assembly process and mechanisms during seed germination of two wheat varieties under simulated microgravity by 16S rRNA gene amplicon sequencing and metabolome analysis. We found that the bacterial community diversity, and network complexity and stability were significantly decreased under simulated microgravity. In addition, the effects of simulated microgravity on the plant bacteriome of the two wheat varieties tended to be consistent in seedlings. At this stage, the relative abundance of Oxalobacteraceae, Paenibacillaceae, Xanthomonadaceae, Lachnospiraceae, Sphingomonadaceae and Ruminococcaceae decreased, while the relative abundance of Enterobacteriales increased under simulated microgravity. Analysis of predicted microbial function revealed that simulated microgravity exposure leads to lower sphingolipid signaling and calcium signaling pathways. We also found that simulated microgravity drove the strengthening of deterministic processes in microbial community assembly. Importantly, some specific metabolites exhibited significant changes under simulated microgravity, suggesting that bacteriome assembly is mediated, at least in part, by metabolites altered by microgravity. The data we present here moves us closer to a holistic understanding of the plant bacteriome under microgravity stress at plant emergence, and provides a theoretical basis for the precise utilization of microorganisms in microgravity to improve plant adaptation to the challenge of cultivation in space.

Simulated microgravity shapes the endophytic bacterial community by affecting wheat root metabolism.

To improve nutrient utilization and pathogenic resistance of plants in space, it is crucial to understand the effects of microgravity on the plant root microbiome. However, the finer details of whether and how microgravity affects the root microbiome remain unclear. Here, we found that simulated microgravity elicits no significant changes in fungal community composition and diversity, whether rhizosphere or endophytic. However, simulated microgravity caused a significant change in the composition and diversity of endophytic bacteria of wheat seedlings, but not in rhizosphere bacteria. The alteration of endophytic bacterial communities demonstrates that wheat seedlings adopt strategies to recruit additional endophytic Enterobacteriaceae and increase the stability of the endophytic bacterial network to respond to the challenge of simulated microgravity. Furthermore, our results also suggest that the corresponding changes in endophytic bacteria under simulated microgravity are closely related to a significant decrease in metabolites of the host's carbon metabolism, flavonoid biosynthesis, benzoxazinoid biosynthesis, and tryptophan metabolism pathways. Our findings reveal details important to our understanding of the impact of gravity on the microbial community of plant seedlings and the theoretical basis for manipulation of microorganisms to ensure efficient plant production in space.

A novel sensitive DNAzyme-based optical fiber evanescent wave biosensor for rapid detection of Pb2+ in human serum.

We describe here a portable DNAzyme-based optical fiber evanescent wave biosensor (OFEWB) for the rapid and sensitive detection of Pb2+ in human serum. Unlike other biosensors, the OFEWB dispensed with the complicated process of attaching biometric elements to the optical fiber, and the optical fiber directly acted as a transducer to transmit the excitation light and simultaneously collected the fluorescence, which could simplify the detection process, avoid the susceptibility to interference from complex environments and strengthen the reusability of the biosensor. The fluorescence (Cy3) labelled substrate sequence (GR-5S-Cy3) could be cleaved under the catalysis of the GR-5 DNAzyme sequence (GR-5E-BHQ2) in the presence of Pb2+; then the released fluorescence labelled fragments could be directly excited and detected by the OFEWB due to the high transmission efficiency of the excitation light and fluorescence in the OFEWB. Several key factors affecting Pb2+ detection were investigated in detail and optimized. Under the optimal conditions, the LOD of Pb2+ in human serum was 9.34 nM (equivalent to 93.4 nM in whole serum) with a detection range of 0-120 nM. The possible matrix interference was evaluated with different spiked human serum samples, and the recovery of Pb2+ ranged from 74.4% to 112.5% with RSD < 14.8%, implying this method had excellent practicability and could be potentially used in analyzing some biomedical samples.

Development of a two-in-one integrated bioassay for simultaneous and rapid on-site detection of Pb2+ and Hg2+ in water.

Exposure to heavy metal pollution represents a serious health risk and requires rapid, sensitive, and accurate detection to protect human health. However, the existing methods had various limitations for simultaneous detection of heavy metals. Herein, a novel two-in-one integrated bioassay was constructed for simultaneous on-site determination of Hg2+ and Pb2+ through combining all-fiber bicolor fluorescence biosensor (ABFB), functional nucleic acids (FNAs), and FRET. Hg2+ biosensor, consisting of BQ-T14 and CY-A14, performed its detection based on specifical binding of Hg2+ and T bases to form T-Hg2+-T mismatch structure. GR-5 DNAzyme, consisting of GR-5S and GR-5E, is applied for Pb2+ biosensor. The higher concentration of Hg2+ and Pb2+ results in the more T-Hg2+-T mismatch structure formed and the GR-5E to cleave the more GR-5S, respectively, thus allowing higher detectable fluorescence intensities in two signal channels. Thanks to high selectivity of two FNAs-biosensors and excellent time-resolved effect of the ABFB, the Hg2+ and Pb2+ could be directly and simultaneously quantitated in 12 min, and had the LODs of 4.22 nM and 1.55 nM, respectively. The satisfied recovery rate of real samples was verified by ICP-OES. Our strategy could serve as a simple and cost-effective on-site high-frequency detection of heavy metal ions.

Dynamic changes in rhizosphere fungi in different developmental stages of wheat in a confined and isolated environment.

As the core food crop of a bioregenerative life support system (BLSS), wheat is susceptible to pathogen infection due to the lack of effective microbial communities in the confined and isolated environment. Therefore, a thorough understanding of the dynamic changes in wheat rhizosphere fungi is of great significance for improving wheat production and ensuring the stability of the BLSS. In the current study, we collected samples of rhizosphere fungi in the four growth stages of wheat grown in the "Lunar Palace 365" experiment. We employed bioinformatics methods to analyze the samples' species composition characteristics, community network characteristics, and FUNGuild function analysis. We found that the species composition of rhizosphere fungi in the wheat at the tillering stage changed greatly in the closed and isolated environment, while the species composition in the seedling, flowering, and mature stage were relatively stable. The results of the FUNGuild function analysis showed that the functions of rhizosphere fungi changed during wheat development. The rhizosphere fungal community was centered on Ascomycota, Mortierellomycota, and Chytridiomycota, and the community showed the characteristics of a "small world" arrangement. The stage of wheat seedlings is characterized by a greater abundance, diversity, and complexity of the network of interactions in the rhizosphere mycorrhiza community, while the tillering stage exhibited a greater clustering coefficient. Based on the changes in species composition, guild function regulation, and community structure differences of the wheat rhizosphere fungi in the BLSS, our study identified the critical fungal species during wheat development, providing a reference for ensuring the health and yield of plants in the BLSS system. KEY POINTS: • The diversity, composition, FUNguild, and network structure of rhizosphere fungi were analyzed. • Ascomycota, Mortierellomycota, and Chytridiomycota were the center of the rhizosphere fungal community network. • The effects of different wheat developmental stages on the community composition, function, and network structure of rhizosphere fungi were examined.

Community dynamics in rhizosphere microorganisms at different development stages of wheat growing in confined isolation environments.

Wheat is the core food crop in bioregenerative life support systems (BLSSs). In confined isolation environments, wheat growth suffers from a lack of stable microbial communities and is susceptible to pathogenic infections due to the culture substrate's limitations. To overcome this limitation, the time series changes of wheat rhizosphere microorganisms in wheat production must be understood. In the present study, we examined the rhizosphere microbial samples from wheat at four different growth stages from plants collected from a BLSS plant cabin. We employed bioinformatics analysis strategies to analyze the characteristics of species composition, function prediction, and community network. The species composition of wheat rhizosphere microorganisms was relatively stable in the seedling, tillering, and flowering stages in confined isolation environments. However, we observed marked microbial changes at mature stages. The results of functional prediction analysis suggest that the rhizosphere microbial community function of "Energy metabolism" gradually decreased, and the function of "Transmembrane transport" gradually increased during wheat development. The construction of the rhizosphere microbial community is non-random, scale-free and has the characteristics of a small world. We found the tillering stage to be more complex than the other stages. Our study reveals the composition characteristics, functional changes, and community structure fluctuations of rhizosphere bacteria at different development stages of wheat in the isolated and controlled environment, providing a theoretical basis for the efficient production of BLSS plant systems. KEY POINTS: • We collected wheat rhizosphere microorganisms at different stages in a confined isolation environment. • The diversity, composition, function, and network structure of rhizosphere bacteria were analyzed. • The effect of different wheat stages on the composition, function, and network structure of rhizosphere microorganisms was speculated.

The beneficial effects of ultraviolet light supplementation on bone density are associated with the intestinal flora in rats.

The general public spends one-third of its time under artificial lighting, which lacks bands beneficial to human health, and long-term exposure will have a negative impact on bone health. Here, we report the effects of long-term, low-dose ultraviolet (UV) supplementation to white light-emitting diode (LED) light exposure on intestinal microorganisms and bone metabolism, as well as the correlations between the two. Normal and ovariectomized rats were irradiated with LED white light with or without supplementation with UV. The effects of UV supplementation on the intestinal flora and the relationship between the intestinal flora and bone were investigated by measuring the intestinal flora, bone metabolism markers, and bone histomorphology. UV supplementation affected the bone density and bone mass by changing the relative content of Firmicutes, Saccharibacteria, and Proteobacteria; however, the intestinal flora were not the only factors affecting bone. Ultraviolet supplementation changed the composition and function of the gut flora in the bone loss model. By increasing the synthesis of short-chain fatty acids and affecting immunomodulatory, intestinal flora directly or indirectly regulate the activity of osteoclasts and thus mediate UV-mediated improvements in bone metabolism. Our work shows that UV supplementation affects bone density by influencing the intestinal flora, introducing a novel strategy to develop healthier artificial light sources and prevent bone loss. KEY POINTS: • We measured the bone metabolism markers and bone histomorphometry of rats. • The diversity, composition, and function of intestinal flora were analyzed. • The relationship between gut microbiota and host bone physiology was analyzed.

The highly efficient removal of HCN over Cu8Mn2/CeO2 catalytic material.

In this work, porous CeO2 flower-like spheres loaded with bimetal oxides were prepared to achieve effective removal of HCN in the lower temperature region of 30-150 °C. Among all samples, the CeO2 loaded with copper and manganese oxides at the mass ratio of 8/2 (Cu8Mn2/CeO2) exhibited the highest catalytic activity: the HCN removal rate was nearly 100% at 90 °C at the conditions of 120 000 h-1 and 5 vol% H2O, the catalytic activity of which was higher than for other reported catalysts. The introduction of MnO x could improve the dispersion of CuO particles and increase the total acid sites of the prepared samples. It was proved that the synergy between CuO and MnO x , the chemisorption oxygen, the oxygen vacancies, the Cu2+ and Mn4+ all played an important role in determining the good catalytic activity of the prepared samples. NH3-TPD analysis indicated the introduction of MnO x promoted the conversion of NH3 and N2 selectivity by increasing the acid sites of the sample. According to the C, N balance data and FT-IR results, when the temperature was below 30 °C, the removal of HCN over Cu8Mn2/CeO2 was mainly by chemisorption and the HCN breakthrough behaviors corresponded to the Yoon and Nelson's model. When temperature was above 120 °C, the HCN was totally removed by catalytic hydrolysis and catalytic oxidation.

Correction: The highly efficient removal of HCN over Cu8Mn2/CeO2 catalytic material.

[This corrects the article DOI: 10.1039/D0RA10177J.].

The effect of wheat seedling density on photosynthesis may be associated with the phyllosphere microorganisms.

Wheat seedlings are significantly impacted by the presence of bacteria. However, bacteria are unavoidably growing together with wheat. The study aimed to reveal wheat photosynthesis, phyllosphere bacterial community composition, and a shift in the bacterial community following different density treatments in a closed artificial ecosystem. Here, we report the relationship between photosynthesis and bacterial community in wheat seedlings for different planting densities. In this closed artificial ecosystem, a total of 30 phyla were detected, with 17 of them were simultaneously present in four treatments, under high light intensity and carbon dioxide growth environment. The key phyla detected include Firmicutes, Proteobacteria, and Bacteroidetes. We found that planting densities significantly impacted the photosynthetic characteristics of wheat and bacterial genetic biodiversity, but not on species composition of the bacterial community. Network analysis shows that the phyllosphere bacteria network structures were characterized by the clustering coefficient and modularity. Network for the 1000 plants/m2 treatment group exhibits the highest levels of average clustering coefficient but lowest modularity and number of modules, among all plant densities tested. In addition, the network for the 1200 plants/m2 treatment group exhibits the best characteristics in terms of net photosynthesis rate and intrinsic water use efficiency, higher complex phyllosphere community network structures, higher abundance of Corynebacterium, and more function of "Amino acid metabolism", which encourages the plants to grow better. The findings presented in this work elucidated the role of plant density in the growth of phyllosphere bacteria during wheat seedlings and provided theoretical support for reasonable wheat density cultivation in closed artificial ecosystems and wheat field production.

Effect of different light intensity on physiology, antioxidant capacity and photosynthetic characteristics on wheat seedlings under high CO2 concentration in a closed artificial ecosystem.

The growth of plants under high carbon dioxide (CO2) concentrations (≥ 1000 ppm) is explored for the climate change and the bioregenerative life support system (BLSS) environment of long-duration space missions. Wheat (Triticum aestivum L.) is a grass cultivated for cereal grain-a global staple food including astronauts. Light and CO2 are both indispensable conditions for wheat seedlings. This study provides insights on the physiology, antioxidant capacity and photosynthetic characteristics of wheat seedlings under a range of photosynthetic photon flux densities in a closed system simulating BLSS with high CO2 concentration. We found that the Fv/Fm, Fv/F0, chlorophyll content, intrinsic water use efficiencies (WUEi), membrane stability index (MSI), and malondialdehyde (MDA) of wheat seedlings grown under an intermediate light intensity of 600 µmol m-2 s-1 environment were all largest. Interestingly, the high light intensity of 1200 mol m-2 s-1 treatment group exhibits the highest net photosynthetic rate but the lowest MDA content. The stomatal conductance and F0 of high light intensity of 1000 µmol m-2 s-1 treatment group were both significantly higher than that of other groups. Our study provides basic knowledge on the wheat growth in different environments, especially in a closed ecosystem with artificial lights.

Morphology and Ultrastructure of Antennal Sensilla in Male and Female Agrilus mali (Coleoptera: Buprestidae).

The apple buprestid beetle, Agrilus mali Matsumura, is an invasive pest causing significant damages to rare wild apple forests of Xinjiang. The morphology, abundance and distribution of antennal sensilla in both sexes of this pest were examined. We found that the antennae of A. mali females were longer than those of males. Five types of antennal sensilla were characterized, including trichodea (subtypes Tr.1, Tr.2, and Tr.3), chaetica (subtypes Sc.1, Sc.2, Sc.3, and Sc.4), basiconica (subtypes Ba. 1, Ba. 2, Ba. 3 and Ba.4), Böhm bristles (subtypes BB. 1, and BB. 2), and multiporous grooved sensilla. The most abundant sensilla of Ba.2 tended to occur mainly on flagellomeres 5-8 in both sexes. The last three flagellomeres tended to have the most abundant Tr.1 in both sexes. Overall, the abundance and distribution of these sensilla appeared to be highly conserved in both sexes, and their olfactory organs seemed to cluster on flagellomeres 6-8. However, some sex dimorphisms were also observed. Tr.3 and BB.2 were found only in females. Sensilla of Sc.2 were found on the pedicel and first two flagellomeres only in males. When compared with males, females showed a higher number of Sc.3, but a lower number of Sc.4 on the pedicel. These results indicate that contact cues could be important in intersexual communication in A. mali. The functional roles of these sensilla and their implications in A. mali behaviors are discussed, and further studies of identified chemosensitive sensilla can provide a foundation for developing semiochemical-based management strategies.

Life-history trait plasticity and its relationships with plant adaptation and insect fitness: a case study on the aphid Sitobion avenae.

Phenotypic plasticity has recently been considered a powerful means of adaptation, but its relationships with corresponding life-history characters and plant specialization levels of insects have been controversial. To address the issues, Sitobion avenae clones from three plants in two areas were compared. Varying amounts of life-history trait plasticity were found among S. avenae clones on barley, oat and wheat. In most cases, developmental durations and their corresponding plasticities were found to be independent, and fecundities and their plasticities were correlated characters instead. The developmental time of first instar nymphs for oat and wheat clones, but not for barley clones, was found to be independent from its plasticity, showing environment-specific effects. All correlations between environments were found to be positive, which could contribute to low plasticity in S. avenae. Negative correlations between trait plasticities and fitness of test clones suggest that lower plasticity could have higher adaptive value. Correlations between plasticity and specialization indices were identified for all clones, suggesting that plasticity might evolve as a by-product of adaptation to certain environments. The divergence patterns of life-history plasticities in S. avenae, as well as the relationships among plasticity, specialization and fitness, could have significant implications for evolutionary ecology of this aphid.