Combination of transcriptomics, metabolomics and physiological traits reveals the effects of polystyrene microplastics on photosynthesis, carbon and nitrogen metabolism in cucumber (Cucumis sativus L.).

Although microplastic pollution has been widely studied, the mechanism by which they influence plant photosynthesis and carbon and nitrogen metabolism remains unclear. We aimed to explore the effects of polystyrene microplastics (PS) on photosynthesis and carbon and nitrogen metabolism in cucumber using 5 µm and 0.1 µm PS particles. The PS treatments significantly reduced the stability of cucumber mesophyll cells and photosynthetic parameters and increased the soluble sugar content in cucumber leaves. The 5 µm PS affected the photosynthetic pathway by changing the expression of enzyme genes required for the synthesis of NADPH and ATP, which decreased the photosynthetic capacity in cucumber leaves. However, 0.1 µm PS altered the genes expression of phosphoenolpyruvate carboxykinase (PEPCK) and phosphoenolpyruvate carboxylase (PEPC), which affected the intercellular CO2 concentration and attenuated the negative effects on photosynthetic efficiency. Additionally, PS reduced the expression levels of nitrate/nitrite transporter (NRT) and nitrate reductase (NR), reducing the nitrogen use efficiency in cucumber leaves and mesophyll cells damage through increased accumulation of reduced glutathione (GSH), γ-glutamylcysteine (γ-GC), and citrulline. This study provides a new scientific basis for exploring the effects of microplastics on plant photosynthesis and carbon and nitrogen metabolism.

Divergent patterns and drivers of leaf functional traits of Robinia pseudoacacia and Pinus tabulaeformis plantations along a precipitation gradient in the Loess plateau, China.

Changes in precipitation patterns in arid and semi-arid regions can reshape plant functional traits and significantly affect ecosystem functions. However, the synchronous responses of leaf economical, anatomical, photosynthetic, and biochemical traits to precipitation changes and their driving factors have rarely been investigated, which hinders our understanding of plants' ecological adaptation strategies to drought tolerance in arid areas. Therefore, the leaf traits of two typical plantations (Robinia pseudoacacia, RP and Pinus tabulaeformis, PT) along the precipitation gradient in the Loess Plateau, including economical, anatomical, photosynthetic, and biochemical traits, were investigated in this study. The results show that the leaf photosynthetic traits of RP and PT increase along the precipitation gradient, whereas leaf biochemical traits decrease. The anatomical traits of PT decrease with increasing precipitation, whereas no significant variation was observed for RP. Random Forest analysis show that LNC, LDMC, Chl, and PRO are leaf traits that significantly vary with the precipitation gradient in both plantations. Correlation analysis reveals that the traits coordination of RP is better than that of PT. The LMG model was used to determine driving factors. The results suggest that MAP explains the variation of PT leaf traits better (30.38%-36.78%), whereas SCH and SPH contribute more to the variation of RP leaf traits (20.88%-41.76%). In addition, the piecewise Structural Equation Model shows that the climate and soil physical and chemical properties directly affect the selected leaf functional traits of RP, whereas only the soil chemical properties directly affect the selected leaf functional traits of PT. The results of this study contribute to the understanding of the ecological adaptation of plants to environmental gradients and highlight that correlations among leaf traits should be considered when predicting plant adaptation strategies under future global change scenarios.

A 3-D Visualization Technique for Bone Remodeling in a Suture Expansion Mouse Model.

Craniofacial sutures play a crucial role beyond being fibrous joints connecting craniofacial bones; they also serve as the primary niche for calvarial and facial bone growth, housing mesenchymal stem cells and osteoprogenitors. As most craniofacial bones develop through intramembranous ossification, the sutures' marginal regions act as initiation points. Due to this significance, these sutures have become intriguing targets in orthopedic therapies like spring-assisted cranial vault expansion, rapid maxillary expansion, and maxillary protraction. Under orthopedic tracing force, suture stem cells are rapidly activated, becoming a dynamic source for bone remodeling during expansion. Despite their importance, the physiological changes during bone remodeling periods remain poorly understood. Traditional sectioning methods, primarily in the sagittal direction, do not capture the comprehensive changes occurring throughout the entire suture. This study established a standard mouse model for sagittal suture expansion. To fully visualize bone remodeling changes post-suture expansion, the PEGASOS tissue clearing method was combined with whole-mount EdU staining and calcium chelating double labeling. This allowed the visualization of highly proliferating cells and new bone formation across the entire calvarial bones following expansion. This protocol offers a standardized suture expansion mouse model and a 3-D visualization method, shedding light on the mechanobiological changes in sutures and bone remodeling under tensile force loading.

Biological characteristics of microRNAs secreted by exosomes of periodontal ligament stem cells due to mechanical force.

BACKGROUND: Orthodontic tooth movement (OTM) has previously been considered an inflammatory process. However, recent studies suggest that exosomes may play an important role in the cellular microenvironment of OTM. microRNAs (miRNAs) are one of the major constituents of exosomes. This study aims to investigate the biological characteristics of miRNAs secreted by exosomes of periodontal ligament stem cells (PDLSCs) due to mechanical forces. MATERIALS AND METHODS: First, we established a mechanical stress model. The PDLSCs were loaded under different force values and exosomes were extracted after 48 h. High-throughput sequencing of exosomal miRNAs was performed to further evaluate their biological functions and underlying mechanisms. RESULTS: The morphology and functions of exosomes were not significantly different between the loading and non-loading PDLSC groups. The optimal loading time and force were 48 h and 1 g/cm2, respectively. After sequencing, gene ontology (GO) and Kyoto encyclopaedia of genes and genomes (KEGG) pathway and network analyses were performed and 10 differentially expressed miRNAs were identified according to a literature search. These are miR-99a-5p, miR-485-3P, miR-29a-3p,miR-21-5p, miR-146a-5p, miR140-3p, miR-1306-5p, miR-126-5p, miR-125a-5p, and miR-23a-3p. LIMITATIONS: Extracting exosomes needs a large amount of PDLSCs. More functional experiments need to be done to confirm the exact mechanism of exosomal miRNAs of PDLSCs due to mechanical force. CONCLUSIONS: The expression levels of miRNAs secreted by PDLSC-derived exosomes due to mechanical force were very different compared to PDLSC-derived exosomes under nonmechanical stress. The function of many of the identified exosomal miRNAs was found to be related to osteoblasts and osteoclasts. Further validation is required. A functional investigation of these miRNA could provide novel insights into their mechanism.

Preparation and Properties of Composite Graphene/Carbon Fiber Pouring Conductive Asphalt Concrete.

To solve the problem of snow on steel bridge areas endangering traffic safety and low road traffic efficiency in winter, conductive gussasphait concrete (CGA) was prepared by mixing conductive phase materials (graphene and carbon fiber) into Gussasphalt (GA). First, through high-temperature rutting test, low-temperature bending test, immersion Marshall test, freeze-thaw splitting test and fatigue test, the high-temperature stability, low-temperature crack resistance, water stability and fatigue performance of CGA with different conductive phase materials were systematically studied. Second, the influence of different content of conductive phase materials on the conductivity of CGA was studied through the electrical resistance test, and the microstructure characteristics were analyzed via SEM. Finally, the electrothermal properties of CGA with different conductive phase materials were studied via heating test and simulated ice-snow melting test. The results showed that the addition of graphene/carbon fiber can significantly improve the high-temperature stability, low-temperature crack resistance, water stability and fatigue performance of CGA. The contact resistance between electrode and specimen can be effectively reduced when the graphite distribution is 600 g/m2. The resistivity of 0.3% carbon fiber + 0.5% graphene rutting plate specimen can reach 4.70 Ω·m. Graphene and carbon fiber in asphalt mortar construct a complete conductive network. The heating efficiency of 0.3% carbon fiber + 0.5% graphene rutting plate specimen is 71.4%, and the ice-snow melting efficiency is 28.73%, demonstrating good electrothermal performance and ice-snow melting effect.

Study on Road Performance of Polyurethane Cold-Recycled Mixture.

To give full play to the advantages of polyurethane as a binder, such as mixing at room temperature, short curing time, and high curing strength, polyurethane was used as the binder of a waste asphalt mixture, and the pavement performance of PCRM (Polyurethane Cold-Recycled Mixture) was analyzed. Firstly, the adhesion performance of polyurethane binder with new and old aggregates was evaluated using the adhesion test. Then, the mix proportion was designed according to the material characteristics, and the reasonable molding process, maintenance conditions, design indexes, and the optimal binder ratio were proposed. Secondly, the high-temperature stability, low-temperature crack resistance, water stability, and compressive resilient modulus of the mixture were evaluated through laboratory tests. Finally, the pore structure and microscopic morphology of polyurethane cold-recycled mixture were analyzed by industrial CT (Computerized Tomography) scanning, and the failure mechanism of polyurethane cold-recycled mixture was revealed. The test results show that the adhesion between polyurethane and RAP (Reclaimed Asphalt Pavement) is good, and the splitting strength of the mixture increases greatly when the ratio of glue to stone reaches 9%. Polyurethane binder has low sensitivity to temperature and poor water stability. With the increase of RAP content, the high-temperature stability, low-temperature crack resistance, and compressive resilient modulus of PCRM showed a decreasing trend. When the RAP content was less than 40%, the freeze-thaw splitting strength ratio of the mixture was improved. After the incorporation of RAP, the interface was more complex and there were many micron-scale holes, cracks, and other defects; after high-temperature immersion, the polyurethane binder appeared to show a certain degree of peeling at the holes of the RAP surface. After freeze-thaw, the polyurethane binder on the surface of the mixture produced many cracks. The study of polyurethane cold-recycled mixture is of great significance to realize green construction.

Study on the Properties of Multi-Walled Carbon Nanotubes (MWCNTs)/Polypropylene Fiber (PP Fiber) Cement-Based Materials.

In order to improve the mechanical properties and durability of cement-based materials, a certain amount of multi-walled carbon nanotubes (MWCNTs) and polypropylene fiber (PP fiber) were incorporated into cement-based materials. The mechanical properties of the multi-walled carbon nanotubes/polypropylene fiber cement-based materials were evaluated using flexural strength tests, compressive strength tests, and splitting tensile tests. The effects of multi-walled carbon nanotubes and polypropylene fiber on the durability of cement-based materials were studied using drying shrinkage tests and freeze-thaw cycle tests. The effects of the multi-walled carbon nanotubes and polypropylene fibers on the microstructure and pore structure of the cement-based materials were compared and analyzed using scanning electron microscopy and mercury intrusion tests. The results showed that the mechanical properties and durability of cement-based materials can be significantly improved when the content of multi-walled carbon nanotubes is 0.1-0.15%. The compressive strength can be increased by 9.5% and the mass loss rate is reduced by 27.9%. Polypropylene fiber has little effect on the compressive strength of the cement-based materials, but it significantly enhances the toughness of the cement-based materials. When its content is 0.2-0.3%, it has the best effect on improving the mechanical properties and durability of the cement-based materials. The flexural strength is increased by 19.1%, and the dry shrinkage rate and water loss rate are reduced by 14.3% and 16.1%, respectively. The three-dimensional network structure formed by the polypropylene fiber in the composite material plays a role in toughening and cracking resistance, but it has a certain negative impact on the pore structure of the composite material. The incorporation of multi-walled carbon nanotubes can improve the bonding performance of the polypropylene fiber and cement matrix, make up for the internal defects caused by the polypropylene fiber, and reduce the number of harmful holes and multiple harmful holes so that the cement-based composite material not only has a significant increase in toughness but also has a denser internal structure.

[Comparison of clear aligners and customized lingual appliance for bimaxillary dentoalveolar protrusion: a retrospective study].

PURPOSE: To compare the treatment effects of clear aligners and customized lingual appliance on treating bimaxillary dentoalveolar protrusion patients with first premolar extractions. METHODS: Fifty-four patients with bimaxillary dentoalveolar protrusion treated in Shanghai Ninth People Hospital were involved in the retrospective study. Twenty-five cases used clear aligners and 29 cases used customized lingual appliance. All of them were treated by extracting 4 first premolars and retracting anterior teeth with strong anchorage. The changes of anterior tooth and soft tissue adduction before and after treatment were compared by lateral cephalometric measurements. SPSS 26.0 software package was used for data analysis. RESULTS: The total course of treatment in the clear aligners group (46.32±7.37 months) was about 10.8 months longer than that in the customized lingual appliance group (35.55±5.90 months) (P＜0.05). There was no significant difference in upper incisor retraction, lower incisor inclination and overjet reduction between the two groups(P＞0.05). There were significant differences in upper lip retraction, lower lip retraction, upper incisor torque reduction, and overbite reduction between the two groups(P＜0.05). Customized lingual appliance group showed a significant improvement of lips retraction and overbite reduction in orthodontic treatment. For the correction of overjet, there was no significant difference between the two groups (P=0.337). The data of U1-OP (the distance between edge of the upper central incisor and the functional occlusal plane) was not in normal distribution, and there was no significant difference between the two groups(P=0.184). CONCLUSIONS: The two techniques can both retract the anterior teeth and lips to improve the profile. However, the customized lingual appliance was more effective in improving the soft tissue profile of patients with bimaxillary dentoalveolar protrusion, with shorter treatment course.

Preparation and Properties of New Thermal Reflective Coating for Asphalt Pavement.

This paper aims to study the applicability of an epoxy resin modification to improve its anti-aging properties, which are conducive to road performance. To achieve this goal, a wide range of laboratory activities were conducted, including an emulsion mixed with epoxy resin and liquid phenolic resin as the coating substrate; surface-modified titanium dioxide, silica, hollow glass beads and sericite powder as functional fillers; then adding pigments and various additives to prepare a new asphalt pavement heat-reflective coating. Secondly, the optimum brushing amount of the coating was obtained, and the cooling effect was clarified. Finally, the road performance was evaluated by testing the coating's skid resistance, wear resistance and impermeability. The results show that the skid resistance, abrasion resistance and impermeability of the heat reflection coating meet the specification requirements.

Carbon dots derived from folic acid attenuates osteoarthritis by protecting chondrocytes through NF-κB/MAPK pathway and reprogramming macrophages.

BACKGROUND: Osteoarthritis (OA) is a common joint disorder worldwide which causes great health and economic burden. However, there remains an unmet goal to develop an effective therapeutic method to prevent or delay OA. Chondrocytes, as the major cells involved in OA progression, may serve as a promising therapeutic target. RESULTS: A kind of carbon dots (CDs) with excellent biocompatibility was fabricated from folic acid via hydrothermal method and could effectively attenuate osteoarthritis. It was demonstrated that CDs treatment could rescue IL1ß-induced proinflammatory responses, oxidative stress, cartilage degeneration and extracellular matrix degradation. Moreover, CDs reprogrammed lipopolysaccharide (LPS)-induced macrophage inflammation and polarization. Conditioned medium (CM) from CDs-treated macrophages could attenuate IL1ß-induced chondrocyte injury. Also, CM from CDs-treated chondrocytes had immunoregulatory functions on macrophages. Mechanistically, CDs inhibited the activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPK) signaling pathways in IL1ß-stimulated chondrocytes. In vivo, anterior cruciate ligament transection (ACLT) mice model was adopted and it was indicated that intra-articular injection of CDs effectively delays OA pathogenesis. CONCLUSIONS: Taken together, these findings indicated CDs could mediate OA via promoting cartilage repair and immunomodulating macrophages within local microenvironment, which may provide evidences for utilizing CDs as a novel nanomaterial for OA treatment.

Electrode Layout Optimization and Numerical Simulation of Cast Conductive Asphalt Concrete Steel Bridge Deck Pavement.

In order to obtain the optimal electrode layout and ice melting effect of cast conductive asphalt concrete steel bridge deck pavement, firstly, pouring conductive asphalt concrete was prepared; secondly, different electrode materials and layout methods were selected to test the heating rate of the specimen from start to 120 min, and the electrode materials and layout methods were optimized. Then, the finite element analysis software ANSYS was used to build the model for heating and ice melting simulation, and the indoor test was used to further verify the ice melting effect of the cast conductive asphalt coagulation with or without the insulation layer. Finally, the thermal-structural coupling analysis of cast conductive asphalt concrete steel bridge deck pavement was carried out using ANSYS finite element software. The results showed that the stainless steel electrode material had the best heating effect, and the electrode thickness in the range of 0.1~3 mm had no effect on the heating effect. The intermediate heating rate of the upper surface of the stainless steel sheet electrode cast conductive asphalt concrete in the left and right external electrodes was 8 ∘C/h, while the intermediate heating rate of the upper surface of the stainless steel mesh electrode cast conductive asphalt concrete was 12.9 ∘C/h. The layout of the left and right buried stainless steel metal mesh was able to effectively improve the snow melting efficiency; ANSYS finite element ice melting simulation was used to obtain the variation law of ice melting efficiency and a temperature field of cast conductive asphalt concrete. The indoor ice melting test showed that when melting the same thickness ice layer at 50 V voltage, it took 240 min with an insulation layer and 720 min without an insulation layer, which was three times that of the ice with an insulation layer, which further verifies the superiority of its ice melting effect. The most unfavorable load position of pavement under load and temperature field was determined. The maximum tensile stress and compressive stress of the pavement surface were transverse, and the maximum shear stress of the pavement bottom was transverse.

Study on Rheological Properties of Graphene Oxide/Rubber Crowd Composite-Modified Asphalt.

In order to improve the durability of asphalt pavement and prolong the service life of heavy traffic asphalt pavement, graphene oxide (GO) and rubber powder (RP) were used as composite modifiers to modify matrix asphalt. The high-temperature rheological properties of composite-modified asphalt at different temperatures and frequencies were analyzed. The influence of different stress levels on the viscoelastic properties of composite-modified asphalt was evaluated. The low-temperature rheological properties of composite-modified asphalt were studied. The difference between RP-modified asphalt and GO/RP composite-modified asphalt was analyzed, and the mechanism of GO and RP on asphalt modification was explored. The results show that the composite-modified asphalt has good rheological properties at low temperature, relatively smooth surface and stable network structure, which improves the segregation problem of RP in matrix asphalt. At present, GO and RP are rarely used as composite modifiers to modify matrix asphalt at home and abroad, which is an innovation in material selection.

Study on Performance of Retarded Composite Semi-Rigid Base Mixed with Rubber Powder.

In order to solve the problem of poor crack resistance and frost resistance of semi-rigid base, rubber powder and retarder were added to a semi-rigid base mixture. First, 61 mixing ratios were determined. Then, through the unconfined compressive strength, splitting strength, and other tests, the mechanical, crack, and frost resistance properties of the retarded composite semi-rigid base coarse mixture with rubber powder were studied. Finally, the macro and micro properties of the two kinds of admixture composite semi-rigid base coarse mixtures were studied by means of SEM and industrial CT. The results show that rubber powder and retarder can effectively improve the cracking and freezing resistance of the mixture. After five freeze-thaw cycle tests, the strength of the retarded composite semi-rigid base material mixed with rubber powder decreased slightly compared with the mixture without additives. It can be seen that rubber powder improved the frost resistance of the mixture. When the content of rubber powder was 1.5%, the BDR value of the mixture increased by 8.8%. With the increase of unconfined compressive strength, splitting strength, and flexural tensile strength at 28 d and 90 d, it was found that the retarder improved the middle and late strength of the mixture. When the content of retarder was 0.09%, the increase of unconfined compressive strength at 28 d reached 3.9%. The addition of rubber powder and retarder improved the distribution of internal pores, the proportion of large pores decreased, and the proportion of small pores increased. The retarder changed the morphology of hydration products, formed a dense network supporting structure, further refined the pores, and reduced the porosity of the mixture. The proportion of pores with a volume greater than 100 mm3 in the total pore volume decreased by 26.01%, and the proportion of medium pores increased by 13.07%, thereby improving the mechanical properties of the mixture.

Histone demethylase JMJD3 downregulation protects against aberrant force-induced osteoarthritis through epigenetic control of NR4A1.

Osteoarthritis (OA) is a prevalent joint disease with no effective treatment strategies. Aberrant mechanical stimuli was demonstrated to be an essential factor for OA pathogenesis. Although multiple studies have detected potential regulatory mechanisms underlying OA and have concentrated on developing novel treatment strategies, the epigenetic control of OA remains unclear. Histone demethylase JMJD3 has been reported to mediate multiple physiological and pathological processes, including cell differentiation, proliferation, autophagy, and apoptosis. However, the regulation of JMJD3 in aberrant force-related OA and its mediatory effect on disease progression are still unknown. In this work, we confirmed the upregulation of JMJD3 in aberrant force-induced cartilage injury in vitro and in vivo. Functionally, inhibition of JMJD3 by its inhibitor, GSK-J4, or downregulation of JMJD3 by adenovirus infection of sh-JMJD3 could alleviate the aberrant force-induced chondrocyte injury. Mechanistic investigation illustrated that aberrant force induces JMJD3 expression and then demethylates H3K27me3 at the NR4A1 promoter to promote its expression. Further experiments indicated that NR4A1 can regulate chondrocyte apoptosis, cartilage degeneration, extracellular matrix degradation, and inflammatory responses. In vivo, anterior cruciate ligament transection (ACLT) was performed to construct an OA model, and the therapeutic effect of GSK-J4 was validated. More importantly, we adopted a peptide-siRNA nanoplatform to deliver si-JMJD3 into articular cartilage, and the severity of joint degeneration was remarkably mitigated. Taken together, our findings demonstrated that JMJD3 is flow-responsive and epigenetically regulates OA progression. Our work provides evidences for JMJD3 inhibition as an innovative epigenetic therapy approach for joint diseases by utilizing p5RHH-siRNA nanocomplexes.

Aberrant Fluid Shear Stress Contributes to Articular Cartilage Pathogenesis via Epigenetic Regulation of ZBTB20 by H3K4me3.

PURPOSE: Osteoarthritis (OA) is a common disease for human beings, characterized by severe inflammation, cartilage degradation, and subchondral bone destruction. However, current therapies are limited to relieving pain or joint replacement and no effective treatment methods have been discovered to improve degenerative changes. Currently, a variety of evidences have indicated that aberrant mechanical stimuli is closely associated with articular joint pathogenesis, while the detailed underlying mechanism remains unelucidated. In the present study, we determined to investigate the impact of excessive high fluid shear stress (FSS) on primary chondrocytes and the underlying epigenetic mechanisms. MATERIALS AND METHODS: Phalloidin staining and EdU staining were used to evaluate cell morphology and viability. The mRNA level and protein level of genes were determined by qPCR, Western blot assay, and immunofluorescence staining. Mechanistic investigation was performed through RNA-sequencing and CUT&Tag sequencing. In vivo, we adopted unilateral anterior crossbites (UAC) mice model to investigate the expression of H3K4me3 and ZBTB20 in aberrant force-related cartilage pathogenesis. RESULTS: The results demonstrated that FSS greatly disrupts cell morphology and significantly decreased chondrocyte viability. Aberrant FSS induces remarkable inflammatory mediators production, leading to cartilage degeneration and degradation. In depth mechanistic study showed that FSS results in more than 10-fold upregulation of H3K4me3, and the modulatory effect of H3K4me3 on cartilage was obtained by directly targeting ZBTB20. Furthermore, Wnt signaling was strongly activated in high FSS-induced OA pathogenesis, and the negative impact of ZBTB20 on chondrocytes was also achieved through activating Wnt signaling pathway. Moreover, pharmacological inhibition of H3K4me3 activation by MM-102 or treatment with Wnt pathway inhibitor LF3 could effectively alleviate the destructive effect of FSS on chondrocytes. In vivo UAC mice model validated the dysregulation of H3K4me3 and ZBTB20 in aberrant force-induced cartilage pathogenesis. CONCLUSION: Through the combination of in vitro FSS model and in vivo UAC model, KMT2B-H3K4me3-ZBTB20 axis was first identified in aberrant FSS-induced cartilage pathogenesis, which may provide evidences for epigenetic-based therapy in the future.

The distribution and impact of polystyrene nanoplastics on cucumber plants.

Microplastic pollution in farmlands has become a source of major concern, but few previous studies have focused on the effect of microplastics on higher plants. In this study, the distribution of polystyrene nanoplastics (PSNPs) of four different particle sizes (100, 300, 500, and 700 nm) was investigated in cucumber plants, and their influence on physiological indexes of the root system and fruit quality was determined. The results showed that PSNPs initially accumulated in the root system before being transported to the aboveground parts of the plant. Finally, they were distributed in the leaves, flowers, and fruits, through the stems. The 300-nm plastic microspheres significantly increased root activity and malondialdehyde (MDA) and proline content of the roots. The results demonstrated that the environmental pressures caused by PSNPs of different particle sizes were different. The amount of soluble protein in cucumber fruits was significantly increased, and the levels of Mg, Ca, and Fe were significantly decreased by PSNPs of different particle sizes. Our findings provide a scientific basis for risk assessment of PSNP exposure in the soil-plant systems.

Composite inclusion complexes containing hyaluronic acid/chitosan nanosystems for dual responsive enrofloxacin release.

In order to overcome treatment difficulty of S. aureus infections, a pH/hyaluronidase dual responsive enrofloxacin-cyclodextrin (ß-CD) inclusion complexes (IC) containing hyaluronic acid/chitosan (HA/CS) self-assemble composite nanosystems covered by poloxamer 188 (F68) was firstly explored for targeted "on-demand" delivery. The FTIR, DSC and PXRD showed that enrofloxacin was embedded into IC and then distributed into F68 coating nanogels formulated by electrostatic interaction between CS and HA. The optimal nanosystems of 118.8 ± 30.7 nm showed excellent stability and responsive release in the acid medium, hyaluronidase containing medium, and LB broth medium where S. aureus present. The nanosystems displayed strong surface adsorption on S. aureus and enhanced activity against S. aureus. It had stronger sustained release than the polymeric nanoparticles formulated by entrapping of IC into F68 and the single HA/CS nanogels. This study provides a promising multi-functionalized nanosystems to overcome the treatment challenge of S. aureus and other bacterial infections.

Physiological response of cucumber (Cucumis sativus L.) leaves to polystyrene nanoplastics pollution.

Microplastics pollution in farmlands has become a major concern. However, few studies have assessed the effects of microplastics on higher plants. In this study, we investigated the influence of polystyrene nanoplastics (PSNPs, 50 mg L-1), with four different particle sizes (100, 300, 500, and 700 nm), on the physiological and biochemical indexes of cucumber leaves. The biomass of cucumber plants significantly decreased after exposure to 300 nm PSNPs. Similarly, the chlorophyll a, chlorophyll b, soluble sugar, carotenoid, and proline content, as well as the fluorescence of cucumber leaves were significantly reduced by 100 nm PSNPs. Malondialdehyde, proline, peroxidase gene expression and enzyme activity, and hydrogen peroxide content significantly increased in cucumber leaves exposed to 700 nm PSNPs. In addition, increasing PSNPs particle size led to decreased relative expression levels and activities of the major antioxidant enzymes superoxide dismutase and catalase, while vitamin C and soluble protein content significantly increased. Overall, our results indicated that PSNPs affect the photosynthetic, antioxidant, and sugar metabolism systems of cucumber leaves, with the latter clearly affecting the total biomass of cucumber plants. The benzene ring resulting from the degradation of PSNPs in cucumber leaves may be the main factor affecting chlorophyll metabolism and sugar metabolism. Our findings provide a scientific basis for the risk assessment of PSNPs exposure in soil-plant systems.

Physiological responses of lettuce (Lactuca sativa L.) to microplastic pollution.

Concerns about the pollution of farmlands by microplastics and the associated toxicology have increased in recent times; however, studies on this topic are scarce. In this study, two kinds of PVC microplastics with different particle sizes (PVC-a with particle sizes from 100 nm to 18 µm, and PVC-b with particle sizes from 18 to 150 µm) and different content levels (0.5%, 1%, and 2%) were used to analyze the effects of PVC microplastics on the physiological characteristics of the lettuce root system and leaves. The results showed that PVC-a and PVC-b had no significant effect on the lettuce root activity. However, 0.5%a and 1%a significantly increased the total length, surface area, volume, and diameter of roots. In terms of leaves, PVC-a and PVC-b had no significant effect on the malondialdehyde content, but 1%a significantly increased the superoxide dismutase activity. Carotenoid synthesis was promoted by PVC-a but inhibited by PVC-b. Furthermore, 1%a could reduce the ability of light energy absorption, dissipation, capture, and electron transfer. The gray correlation analysis indicated that PVC-a correlated to a considerable degree with the indices related to photosynthesis, while PVC-b was significantly correlated with the indices related to root morphology. This study provides insights into the ecotoxicological effect of microplastics on farmland crops and associated ecological risk assessment.

[Role of rate-limiting step of mevalonate pathway in improving lycopene production in Escherichia coli].

The introduction of the mevalonate pathway (MVA pathway) in recombinant Escherichia coli can improve the synthesis of terpenoids. But the imbalance expression of MVA pathway genes and accumulation of intermediates inhibit cell growth and terpenoids production. In this study, each gene of MVA pathway and key genes of lycopene synthesis pathway were cloned in plasmid to express in the recombinant E. coli LYC103 with optimizing the expression of the key genes of the 2-methyl-D-erythritol-4-phosphate pathway (MEP pathway), chromosome recombinant MVA pathway and the lycopene synthesis pathway. The results showed that the overexpression of ispA, crtE, mvaK1, idi and mvaD genes did not affect the cell growth, while lycopene production increased by 13.5%, 16.5%, 17.95%, 33.7% and 61.1% respectively, indicating that these genes may be the rate-limiting steps for the synthesis of lycopene. mvaK1, mvaK2, mvaD of MVA pathway were the rate-limiting steps and were in an operon. The mvaK1, mvaK2, mvaD operon was regulated by mRS (mRNA stabilizing region) library in front of mvaK1, obtaining strain LYC104. Lycopene yield of LYC104 was doubled and cell growth was increased by 32% compared with the control strain LYC103. CRISPR-cas9 technology was used to integrate idi into chromosome at lacZ site to obtain LYC105 strain. Cell growth of LYC105 was increased by 147% and lycopene yield was increased by 2.28 times compared with that of LYC103. In this study, each gene of lycopene synthesis pathway was expressed in plasmid to certify the rate-limiting gene based on the complete MVA pathway on the chromosome. Then the rate-limiting gene was integrated in chromosome with homologous recombination to release the rate-limiting, which providing a new strategy for the construction of high-yield strains for metabolic engineering.