Fast and cost-effective preparation of plant cells for scanning electron microscopy (SEM) analysis

Differences in the uptake and translocation of differentially charged microplastics by the taproot and lateral root of mangroves

The interception of microplastics (MPs) by mangrove roots plays an indispensable role in reducing the environmental risks of MPs. However, there remains limited research on the fate of the intercepted MPs. Hereby, the uptake and subsequent translocation of 0.2 μm and 2 μm PS MPs with different coating charge by the typical salt-secreting mangrove plants (Aegiceras corniculatum) were investigated. Compared to amino-functionalized PS with positive charge (PS-NH2), the visualized results indicated that the efficient uptake of carboxy-functionalized PS with negative charge (PS-COOH) was more dependent on taproots. But for the lateral roots, it only allowed the entry of PS-NH2 instead of PS-COOH. The specific uptake pathways of PS-NH2 on the lateral roots could attribute to the release of H+ and organic acids by root hairs, as well as the relative higher Zeta potential. After entering the Aegiceras corniculatum roots, the translocation of PS MPs was restricted by their particle sizes. Furthermore, the release of PS MPs from Aegiceras corniculatum leaf surfaces through the salt glands and stomata was observed. And the decline in the photochemical efficiency of leaves under PS MPs exposure also indirectly proved the foliar emission of PS MPs. Our study improved the understanding of the environmental behaviors and risks of the retained MPs in mangroves.

Activities of polysaccharide fractions from corn silk: Hemostatic, immune, and anti-lung cancer potentials

Corn silk is the stigma and style of corn and is rich in polysaccharides. Despite the extensive research on its polysaccharides, the hemostatic characteristics of effective parts and the related activities remain insufficiently explored. Corn silk polysaccharide (CSP) was extracted with hot water and purified using a diethylaminoethyl cellulose membrane. Then, it was separated with sephadex G-150 to obtain five fractions. These fractions were investigated for their potential in hemostasis, antioxidant, immune response, and anti-lung cancer activities. CSP-2, CSP-3, and CSP-4 significantly affected the coagulation indicators activated partial thromboplastin time (APTT) and thrombin time (TT) at 125-500 μg/mL. Corn silk flavonoids and saponins at 32.25 μg/mL significantly prolonged APTT, TT, and prothrombin time (PT). CSP-2, with potent antioxidant ability, approaches Vitamin C. At 25 μg/mL, CSPs nearly reached the phagocytosis of neutral red of lipopolysaccharides. The five fractions promoted the proliferation of RAW264.7 cells at 25-800 μg/mL and stimulated NO secretion at 25-100 μg/mL. CSP-2 also showed an 86 % inhibition rate effect on A549 at 200 μg/mL. These results indicate that CSP not only has hemostatic effects but also has immune and anti-lung cancer activities. Thus, it is a potential candidate compound with immune activity for managing bleeding in cancer.

Saline dry fixation for improved cell composition analysis using Raman spectroscopy

Raman spectroscopy enables the label-free assessment of cellular composition. While live cell analysis is the most accurate approach for cellular Raman spectroscopy, the analysis of fixed cells has proved to be very useful, particularly in collaborative projects where samples need to be serially examined by different laboratories or stored and reanalyzed at a later date. However, many chemicals that are widely used for cell fixation directly affect cellular biomolecules, yielding Raman spectra with missing or altered information. In this article, we compared the suitability of dry-fixation with saline versus chemical fixatives. We compared the Raman spectroscopy of saline dry-fixed cells with the more commonly used formaldehyde and methanol fixation and found that dry-fixed cell spectra preserved more cellular information than either chemical fixative. We also assessed the stability of dry-fixed cells over time and found that they were stable for at least 5 months. Finally, a comparison of dry-fixed and live cell spectra revealed effects due to the hydration state of the cells since they were recovered upon rehydrating dry-fixed samples. Thus, for fixed cell Raman spectroscopy, we recommend dry-fixation with unbuffered saline as a superior method to formaldehyde or methanol fixation.

Removal of copper by Azolla filiculoides and Lemna minor: phytoremediation potential, adsorption kinetics and isotherms

Phytoremediation is an eco-friendly biotechnology with low costs. The removal of copper (Cu) from polluted water by the two floating plant species Azolla filiculoides and Lemna minor was observed and recorded. Plants were exposed to different Cu (II) concentration (0.25–1.00 mg/L) and sampling time (Days 0, 1, 2, 5 and 7). Both plants can remove Cu at 1.00 mg Cu/L water, with the highest removal rates of 100% for A. filiculoides and 74% for L. minor on the fifth day of exposure. At the end of the exposure period (Day 7), the growth of A. filiculoides exposed to 1.00 mg Cu/L was inhibited by Cu, but the structure of the inner cells of A. filiculoides was well organized as compared to the initial treatment period. Regarding L. minor, Cu at 1.00 mg/L negatively impacted both the growth and morphology (shrinking of its inner structure) of this plant. This is due to the higher accumulation of Cu in L. minor (2.86 mg/g) than in A. filiculoides (1.49 mg/g). Additionally, the rate of Cu removal per dry mass of plant fitted a pseudo-second order model for both plants, whereas the adsorption equilibrium data fitted the Freundlich isotherm, indicating that Cu adsorption occurs in multiple layers. Based on the results, both species can be applied in the phytoremediation of Cu-polluted water.

Physiological responses of Pichia stipitis to imidazolium chloride ionic liquids with different carbon chain length

Ionic liquids (ILs) are used as detoxication agents for fermentation of lignin into ethanol because of their good applicability. However, the residual ILs may be toxic to the yeast. In order to improve the use of ILs for fermentation and protected environment, the toxicity of ILs with different carbon chain length to Pichia stipitis was studied in this paper. Four kinds of common imidazolium chloride ILs ([C₄mim]Cl, [C₆mim]Cl, [C₈mim]Cl and [C₁₀mim]Cl) were selected. ILs can inhibit the proliferation of Pichia stipitis and increase their mortality. Oxidative stress reaction occurred in the cells, and the activities of antioxidant enzymes are affected. Comparing with the integrated biomarker response (IBR) index, it was found that the toxicity increases with increasing chain length. ILs may enter cells by damaging cell membranes and reduce ethanol production by damaging organelles such as mitochondria. ILs caused wrinkles and dents on the surface of cells up to cell deformation and even rupture. The toxicity sequence was as follows: [C₁₀mim]Cl> [C₈mim]Cl>[C₆mim]Cl>[C₄mim]Cl. Due to this toxicity to Pichia stipitis, these compounds should be used carefully in the fermentation process and also to avoid toxic effects on other organisms in the environment.

Analysis of the biodegradation and phytotoxicity mechanism of TNT, RDX, HMX in alfalfa (Medicago sativa)

The aim of this study was to reveal the mechanism underlying the toxicity of TNT (trinitrotoluene), RDX (cyclotrimethylene trinitroamine), and HMX (cyclotetramethylene tetranitramine) explosives pollution in plants. Here, the effects of exposure to these three explosives were examined on chlorophyll fluorescence, antioxidant enzyme activity, and the metabolite spectrum in alfalfa (Medicago sativa) plants. The degradation rates for TNT, RDX, and HMX by alfalfa were 26.8%, 20.4%, and 18.4%, respectively, under hydroponic conditions. TNT caused damage to the microstructure of the plant roots and inhibited photosynthesis, whereas RDX and HMX induced only minor changes. Exposure to any of the three explosives caused disturbances in the oxidase system. Non-targeted metabolomics identified a total of 6185 metabolites. TNT exposure induced the appearance of 609 differentially expressed metabolites (189 upregulated, 420 downregulated), RDX exposure induced 197 differentially expressed metabolites (155 upregulated and 42 downregulated), and HMX induced 234 differentially expressed metabolites (132 upregulated and 102 downregulated). Of these differentially expressed metabolites, lipids and lipid-like molecules were the main metabolites induced by explosives poisoning. TNT mainly caused significant changes in the alanine, aspartate, and glutamate metabolism metabolic pathways, RDX mainly caused disorders in the arginine biosynthesis metabolic pathway, and HMX disrupted the oxidative phosphorylation metabolic pathway. Taken together, the results show that exposure to TNT, RDX, and HMX leads to imbalances in plant photosynthetic characteristics and antioxidant enzyme systems, changes the basic metabolism of plants, and has significant ecotoxicity effects.

A Hybrid Crack Detection Approach for Scanning Electron Microscope Image Using Deep Learning Method

The scanning electron microscope (SEM) is widely used in the analysis and research of materials, including fracture analysis, microstructure morphology, and nanomaterial analysis. With the rapid development of materials science and computer vision technology, the level of detection technology is constantly improving. In this paper, the deep learning method is used to intelligently identify microcracks in the microscopic morphology of SEM image. A deep learning model based on image level is selected to reduce the interference of other complex microscopic topography, and a detection method with dense continuous bounding boxes suitable for SEM images is proposed. The dense and continuous bounding boxes were used to obtain the local features of the cracks and rotating the bounding boxes to reduce the feature differences between the bounding boxes. Finally, the bounding boxes with filled regression were used to highlight the microcrack detection effect. The results show that the detection accuracy of our approach reached 71.12%, and the highest mIOU reached 64.13%. Also, microcracks in different magnifications and in different backgrounds were detected successfully.