Dynamic Transmission Electron Microscopy Research Articles

Microalgae polyphosphate nanoparticles deliver bioavailable calcium against phytate antagonism: Ex vivo and in vivo studies

Biogenic nanoparticles are promising carriers to deliver essential minerals. Here, calcium-enriched polyphosphate nanoparticles (CaPNPs) with a Ca/P molar ratio > 0.5 were produced by Synechococcus sp. PCC 7002 in the growth medium containing 1.08 g/L CaCl2, and had nearly spherical morphologies with a wide size distribution of 5–75 nm and strongly anionic surface properties with an average ζ-potential of –39 mV, according to dynamic light-scattering analysis, transmission and scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The ex-vivo ligated mouse ileal loop assays found that calcium in CaPNPs was readily available to intestinal absorption via both ion channel-mediated and endocytic pathways, specifically invoking macropinocytic internalization, lysosomal degradation, and transcytosis. Rat oral pharmacokinetics revealed that CaPNPs had a calcium bioavailability approximately 100 % relative to that of CaCl2 and more than 1.6 times of that of CaCO3. CaPNPs corrected the retinoic acid-induced increase in serum calcium, phosphorus, and bone-specific alkaline phosphatase, and decrease in serum osteocalcin, bone mineral content/density, and femoral geometric parameters with an efficacy equivalent to CaCl2 and markedly greater than CaCO3. In contrast to CaCl2, CaPNPs possessed desirable resistance against phytate’s antagonistic action on calcium absorption in these ex vivo and in vivo studies. Overall, CaPNPs are attractive as a candidate agent for calcium supplementation, especially to populations on high-phytate diets.

Development and physicochemical characterization of Azadirachta indica seed oil loaded niosomes nanoparticles: A potential natural pesticide

Nanotechnology has helped for decades to transform the agricultural system to make it more effective and to ensure the worlds food supply is sustainable and secure. However, potential toxicological affects, interactions with the biotic or abiotic environment, high cost, unknown life cycles of nanomaterials, and their possible increased bioaccumulation effects are some of the barriers which needs to be addressed. This study evaluates development and potential agricultural application of niosomes nanoparticles loaded with Azadirachta indica seed oil. Niosomes are organic nanomaterials composed of non-ionic surfactants, which are inexpensive, have good encapsulation efficiency, more stability, relatively nontoxic, and biodegradable. Azadirachta indica seed oil loaded niosomes were prepared by thin-film hydration method utilizing different molar ratios of surfactant (Tween 80) and stabilizer (Soy lecithin). The characteristics of niosomes were determined by Fourier Transform Infra-Red Spectroscopy, Dynamic Light Scattering, Optical Microscope, and Transmission Electron Microscopy. Further, the prepared niosomes were statistically optimized using the Box-Behnken experimental design. The optimized condition displayed optimum particle size (<100 nm) and acceptable percentage entrapment efficiencies (> 80%). Anti-microbial efficacy of loaded niosomes were evaluated against plant pathogens Xanthomonas and Pantoea. The prepared niosomes displayed considerable antimicrobial properties and can be potentially used in agriculture for the targeted delivery of natural pesticides (Azadirachta indica seed oil) to combat agricultural diseases.

Formulation and assessment of penetration potential of Risedronate chitosan nanoparticles loaded transdermal gel in the management of osteoporosis: In vitro and ex vivo screening

Osteoporosis targeting by transdermal distribution has drawn a lot of attention as a cutting-edge, environmentally friendly platform for sustainable pain management. We investigate a novel biocompatible transdermal gel (RCNGL) containing biodegradable chitosan nanoparticles and Risedronate (RS) to treat osteoporosis. The RCNGL was formulated using the Pluronic F 127 co-polymer system and the ionic gelation process. The formulation showed a robust architecture of nanoparticle dispersion with a nano-size range of 201.8 nm when it was thoroughly analysed for Scanning Electron Microscopy, Dynamic electron Microscopy and transmission electron microscopy. At various temperatures, the entrapment efficiency was 67.53±1.05% with steady rheology and respectable porosity, validating FT-IR spectra that showed structural compatibility of RS with other excipients. The drug release test resulted in an 88% RS gel release, supporting sustained release kinetics. The ex vivo Franz diffusion study and in vitro cell uptake and distribution experiments revealed clear cell uptake and distribution with notable skin permeation displaying >70% RS release in mouse epidermal tissue. Overall, our research shows that biodegradable RCNGL may offer a potential osteoporosis and pain control strategy in clinical platforms using passive targeting.

Spatial-temporal characterization of photoemission in a streak-mode dynamic transmission electron microscope.

A long-standing motivation driving high-speed electron microscopy development is to capture phase transformations and material dynamics in real time with high spatial and temporal resolution. Current dynamic transmission electron microscopes (DTEMs) are limited to nanosecond temporal resolution and the ability to capture only a few frames of a transient event. With the motivation to overcome these limitations, we present our progress in developing a streak-mode DTEM (SM-DTEM) and demonstrate the recovery of picosecond images with high frame sequence depth. We first demonstrate that a zero-dimensional (0D) SM-DTEM can provide temporal information on any local region of interest with a 0.37 μm diameter, a 20-GHz sampling rate, and 1200 data points in the recorded trace. We use this method to characterize the temporal profile of the photoemitted electron pulse, finding that it deviates from the incident ultraviolet laser pulse and contains an unexpected peak near its onset. Then, we demonstrate a two-dimensional (2D) SM-DTEM, which uses compressed-sensing-based tomographic imaging to recover a full spatiotemporal photoemission profile over a 1.85-μm-diameter field of view with nanoscale spatial resolution, 370-ps inter-frame interval, and 140-frame sequence depth in a 50-ns time window. Finally, a perspective is given on the instrumental modifications necessary to further develop this promising technique with the goal of decreasing the time to capture a 2D SM-DTEM dataset.

Direct Optical Particle Tracking - a technique for size distribution assessment

Nanotechnology, an emerging discipline within material science, has ushered in a new era of engineering by creating nanostructured materials with distinctive properties suitable for a wide range of bioengineering applications. The shape and size of these materials constitute critical variables, determined by the chosen synthesis method and chemical precursors. Silver nanoparticles, synthesized through chemical processes, exhibit antibacterial properties when their size falls within a specific range. However, measuring the size of such nanoparticles, typically in the nanometer to tens of nanometers range, necessitates specialized techniques like Dynamic Light Scattering and Transmission Electron Microscopy. These methods are often limited by assumptions, high costs and longer measurement times. This paper introduces a novel approach utilizing Direct Particle Tracking for assessing particle size distribution in the early stages of nanoparticle synthesis. The study used realistic computer simulations of nanoparticle diffusion, employing the CHODIN code and a specific code for Direct Particle Tracking written for this purpose. The Brownian motion of each particle is recorded, the mean square displacement is computed and the diffusion coefficient, as well. The diameter of each particle is assessed and here from the particle distribution. The results on simulated particle diffusion demonstrate the feasibility of using Direct Particle Tracking as an effective method for size distribution assessment in the initial phases of nanoparticle synthesis. This innovation opens the door to real-time monitoring and control of nanoparticle size in bioengineering applications, promising significant advancements in the field of nanotechnology.

Plackett-Burman design in the biosynthesis of silver nanoparticles with Mutisia acuminatta (Chinchircoma) and preliminary evaluation of its antibacterial activity.

Background: The aim of this study was to synthesize silver nanoparticles (AgNPs) using the methanolic fraction of Mutisia acuminatta leaves using Plackett-Burman design to optimize process parameters and to evaluate its antibacterial effect. Methods: For the separation of Mutisia acuminatta phytoconstituents, chromatographic techniques were used. For characterization and identification, UV - VIS spectrophotometry, FTIR spectrophotometry, Dynamic Light Scattering (DLS) and transmission electron microscopy (TEM) were used. The Plackett-Burman design used polynomial regression statistical analysis to determine the most influential variables. Results: UV-VIS spectroscopy reported an absorbance concerning surface plasmon resonance between 410-420 nm wavelength for the AgNPs. FTIR spectrophotometry reported characteristic peaks in the biosynthesized AgNPs, observing the disappearance of spectral peaks between 1000-1500 cm -1. By UHPLC-MS, caffeic acid derivatives, coumarins, flavonoids, lignans, disaccharide and a complex formed between silver and the solvent (AgCH3CN+) were identified. Using DLS, the AgNPs presented an average hydrodynamic size of 45.91 nm. TEM determined the spherical shape of the AgNPs, presenting diameters in the range of 30 to 60 nm. The biosynthesized AgNPs showed higher antibacterial activity against Escherichia coli and Staphylococcus aureus than the total extract, the methanolic fraction and pure methanol. The polynomial model in the biosynthesis was validated with an adequate fitting representing the experimental data of the process. The most significant variables for the model obtained were the reaction pH (X 2) and the concentration of the precursor salt AgNO 3 (X 6). Conclusions: The synthesized AgNPs offer a viable option for further development due to the presence of bioactive compounds, adequate characterization and antibacterial activity.

Optimization of Synthesis of Silver Nanoparticles Conjugated with Lepechinia meyenii (Salvia) Using Plackett-Burman Design and Response Surface Methodology—Preliminary Antibacterial Activity

In the present investigation, an ethanolic fraction (EF) of Lepechinia meyenii (salvia) was prepared and fractionated by gradient column chromatography, and the main secondary metabolites present in the EF were identified by HPLC-MS. Silver nanoparticles (AgNPs) were synthesized and conjugated with the EF of Lepechinia meyenii (salvia). The AgNPs synthesis was optimized using Plackett-Burman design and response surface methodology (RSM), considering the following independent variables: stirring speed, synthesis pH, synthesis time, synthesis temperature and EF volume. The AgNPs synthesized under the optimized conditions were characterized by UV visible spectroscopy (UV-VIS), Fourier Transform Infrared Spectroscopy (FT-IR), Dynamic Light Scattering (DLS) and Scanning Transmission Electron Microscopy (STEM). The antibacterial activity of the AgNPs against Staphylococcus aureus (ATCC® 25923) was evaluated. The following flavonoids were identified: rosmarinic acid, diosmin and hesperetin-7-O-rutinoside. The optimized conditions for the synthesis of nanoparticles were pH 9.45, temperature 49.8 °C, volume of ethanolic fraction 152.6 µL and a reaction time of 213.2 min. The obtained AgNPs exhibited an average size of 43.71 nm and a resonance plasmon of 410–420 nm. Using FT-IR spectroscopy, the disappearance of the peaks between 626.50 and 1379.54 cm−1 was evident with the AgNPs, which would indicate the participation of these functional groups in the synthesis and protection of the nanoparticles. A hydrodynamic size of 47.6 nm was obtained by DLS, while a size of 40–60 nm was determined by STEM. The synthesized AgNPs conjugated with the EF showed a higher antibacterial activity than the EF alone. These results demonstrate that the AgNPs synthesized under optimized conditions conjugated with the EF of the Lepechinia meyenii (salvia) presented an increased antibacterial activity.

Lyophilised nanovesicles loaded with vitamin B12

The use of nanomaterials in recent years has shown many advantages for the production of pharmaceuticals, cosmetics, food, and food packaging. Nanovesicles are emerging as carriers of bio-compounds and drugs at a wide variety of applications due to the hydrophilic and lipophilic character of the structure: an aqueous core surrounded by a lipid layer. In this work, vitamin B12 (cobalamin) was encapsulated, due to its synergic activity with antibiotics. Moreover, this bio compound is present in several food products and pharmaceuticals products. A freeze-drying process is proposed for nanocarriers developments, due to its advantages for storage and transportation. Three types of vesicles formulations were tested: liposomes, niosomes and positively charged niosomes. Maltodextrin at 20 % concentration (w/w) was added to the formulation to protect the vesicles during the lyophilisation process. The nanovesicles particle size and morphology was characterized by Dynamic Light Scattering and Transmission Electron Microscopy, and the encapsulation efficiency by HPLC with UV–vis’s detection. The lyophilised powder was resuspended in three aqueous phases: pure water, glycerol and PEG400 aqueous solutions. An increase in the mean vesicle size was observed as a general trend. It was also studied the effect of adding vitamin B12 before or after the lyophilisation step on mean vesicles size, results indicated that vesicles were less affected in size when vitamin B12 was added before the lyophilisation step. Moreover, encapsulation efficiency (EE) of vitamin B12 in lyophilised vesicles arise values up to 70 % while the loading capacity (LC) of these systems were 100 mg/g, values obtained for liposomes when PEG400 solution was used as hydrating media, showing that the method developed for loaded lyophilised nanocarriers do not alter EE and LC.

Biosynthesis and antibacterial activity of silver nanoparticles using Flos Sophorae Immaturus extract

The current study proposes a green synthesis method for silver nanoparticles (Ag NPs) using various concentrations of Flos Sophorae Immaturus extract as reducing and capping agents. The UV-Visible (UV-Vis) spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) were used to characterize resulting brown nanopowder. The as-prepared Ag NPs had a high negative zeta potential value of ∼ -38 mv, indicating the existence of electrostatic stabilization. The average sizes of ∼27.8 nm, 28.5 nm, 34.3 nm and 36.5 nm were measured by TEM. Moreover, FTIR and XPS analyses validated the production and chemical composition of Ag NPs from silver nitrate. The antibacterial activity of Ag NPs was examined against E. coli, P. aeruginosa, and S. aureus using agar well diffusion and the minimum inhibitory concentration (MIC) method. The antibacterial activity of the as-prepared Ag NPs from 4 mL extract was excellent against E. coli, P. aeruginosa, and S. aureus and the MIC values were 31.250, 15.625, and 31.250 mg/L, respectively. Based on these results, this study proposes a practical approach for the synthesis of Ag NPs in the industry and medical fields.

Green synthesis of silver nanoparticles using Cinnamomum tamala (Tejpata) leaf and their potential application to control multidrug resistant Pseudomonas aeruginosa isolated from hospital drainage water

Green Synthesis of Metal Nanoparticles is becoming a more common method for producing nanoparticles with a diameter of 1–100 nm that may be employed in a variety of medical applications. The antibacterial efficacy of silver nanoparticles (AgNPs) derived from Cinnamomum tamala (Tejpata) leaf extract against antibiotic-resistant Pseudomonas aeruginosa is investigated in this study. Green AgNP synthesis is safe, cost-effective, and ecologically friendly. The biosynthesized AgNPs were studied using UV-Visible spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). The AgNPs were virtually spherical, with an average size of 25–30 nm, according to TEM observations. Biochemical and molecular identification were used to isolate multidrug-resistant P. aeruginosa from the hospital's drainage water. The antibacterial potential of AgNPs against P. aeruginosa is determined using the agar diffusion method. Silver nanoparticles produced from Cinnamomum tamala (Tejpata) leaf extract were shown to be effective in inhibiting four strains of P. aeruginosa. According to the agar disc diffusion method, AgNPs had the largest inhibition zone of 17.67 ± 0.577 mm, while aqueous extract had 5.67 ± 0.5777 mm, indicating that AgNPs had antibacterial activity. This study on AgNPs might assist with managing multidrug resistant pathogenic bacteria and be a possible source of medicinal application due to its potential antibacterial effect.

Marine plant mediated green synthesis of silver nanoparticles using mangrove Rhizophora stylosa: Effect of variable process and their antibacterial activity.

Background:Most natural plants used in the synthesis of silver nanoparticles are limited to marine plants. To carry out applications, colloidal silver nanoparticles (AgNps) should have appropriate properties such as homogeneous shapes, small and narrow particle size distribution, and long time stability. This study aims to determine the effects of a variable process of AgNps mediated mangrove Rhizophora stylosa (RS) leaf extract, and antibacterial activity. Methods: Synthesis of AgNps was carried out by stirring silver nitrate solution with aqueous extract. The characterization of AgNps was carried out using UV-Vis spectrophotometry, X-ray diffraction (XRD), Dynamic Light Scattering (DLS) zetasizer and Transmission Electron Microscopy (TEM). Evaluation of antibacterial activity was carried out on E scherichia coli and Staphylococcus aureus. Reaction conditions such as the concentration of metal ions (0.001 M, 0.005 M, and 0.01 M), extracts (1%, 3%, and 5% v/v), and the reaction time on the size and stability of nanoparticles were also explored. Results: The UV-Vis spectroscopy showed an absorption of colloidal AgNps in a wavelength range of 403-443 nm. TEM analysis showed that as-synthesized AgNps were spherical in shape with a size range of 5-87 nm. The use of 0.001 M and 0.005 M of Ag + resulted in a smaller diameter than the synthesized AgNps, using 0.01 M Ag +, in the same extract concentration. The range of zeta potential was -24.9 mV to -27.7 mV. The as-synthesized AgNps were stable for more than one month. The XRD analysis showed four peaks, which were attributed to the face centered cubic crystal structure of metallic silver. The results of the silver nanoparticles synthesis showed good activity on E scherichia coli and Staphylococcus aureus, with an inhibition zone between 4.1-7.2 mm. Conclusions: The AgNps synthesized with RS leaf extract, which is a reducing agent, showed good potential as an antibacterial component.

Exploring the reinforcing mechanism and micromechanical models for the interphase characteristics in melt mixed XLPE‐fumed SiO2 nanocomposites

AbstractWe present an experimental and theoretical exploration of well‐dispersed, distinctively stable, fumed SiO2 crosslinked polyethylene (XLPE) nanocomposites. The mechanical properties of fumed SiO2 /XLPE nanocomposites were assessed with different concentrations of fumed SiO2, which had noticed that network morphology was immensely influential for the performance of mechanical properties. A reasonable exploration of micromechanical models of composites indicated that the theories of Nicolais–Narkis, and Pukanszky provided an excellent fit to yield strength data of the composites considering the effect of the interphase between XLPE and SiO2. Furthermore, it highlights that the experimental data can be superimposed with the static micromechanical models of Nicolais–Narkis, and Pukanszky. Owing to the proper dispersion of the SiO2 nanospheres in the XLPE matrix, the filler‐polymer interactions are found to be enhanced. Moreover, it resulted in the excellent insulation properties of the nanocomposites, which makes it a better candidate for electrical cable insulating materials. The combined results of structural characterizations by Fourier Transform Infrared Spectroscopy (FTIR), X‐Ray Diffraction (XRD), Differential Scanning Calorimeter (DSC), Dynamic Mechanical Analysis (DMA), Atomic Force, and Transmission Electron Microscopy (AFM, TEM) confirmed the role of fumed SiO2 as a reinforcing mediator in the current system.

Development of Submicrocapsules Based on Co-Assembled Like-Charged Silica Nanoparticles and Detonation Nanodiamonds and Polyelectrolyte Layers.

Capsules with shells based on nanoparticles of different nature co-assembled at the interface of liquid phases of emulsion are promising carriers of lipophilic drugs. To obtain such capsules, theoretically using the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory and experimentally using dynamic light-scattering (DLS) and transmission electron microscopy (TEM) methods, the interaction of like-charged silica nanoparticles and detonation nanodiamonds in an aqueous solution was studied and their ratios selected for the formation of submicron-sized colloidosomes. The resulting colloidosomes were modified with additional layers of nanoparticles and polyelectrolytes, applying LbL technology. As a model anti-cancer drug, thymoquinone was loaded into the developed capsules, demonstrating a significant delay of the release as a result of colloidosome surface modification. Fluorescence flow cytometry and confocal laser scanning microscopy showed efficient internalization of the capsules by MCF7 cancer cells. The obtained results demonstrated a high potential for nanomedicine application in the field of the drug-delivery system development.

Multiframe Imaging of Micron and Nanoscale Bubble Dynamics

Here, we report on the direct sequential imaging of laser-induced cavitation of micron and nanoscale bubbles using Movie-Mode Dynamic Transmission Electron Microscopy (MM-DTEM). A 532 nm laser pulse (∼12 ns) was used to excite gold nanoparticles inside a ∼1.2 μm layer of water, and the resulting bubbles were observed with a series of nine electron pulses (∼10 ns) separated by as little as 40 ns peak to peak. Isolated nanobubbles were observed to collapse in less than 50 ns, while larger (∼2-3 μm) bubbles were observed to grow and collapse in less than 200 ns. Temporal profiles were generally asymmetric, possibly indicating faster growth than collapse dynamics, and the collapse time scale was found to be consistent with modeling and literature data from other techniques. More complex behavior was also observed for bubbles within proximity to each other, with interaction leading to longer lifetimes and more likely rebounding after collapse.

Hepatitis B core antigen modulates exosomal miR-135a to target vesicle-associated membrane protein 2 promoting chemoresistance in hepatocellular carcinoma.

BACKGROUNDHepatocellular carcinoma (HCC) is one of the most common malignant tumors. The association of hepatitis B virus (HBV) infection with HCC is hitherto documented. Exosomal miRNAs contribute to cancer progression and chemoresistance. HBV X protein has been known to modulate miRNAs that facilitate cell proliferation and the process of hepatocarcinogenesis. However, there has been no report on hepatitis B core antigen (HBc) regulating exosomal miRNAs to induce drug resistance of HCC cells.AIMTo elucidate the mechanism by which HBc promotes Doxorubicin hydrochloride (Dox) resistance in HCC.METHODSExosomes were isolated by ultracentrifugation. The morphology and size of exosomes were evaluated by Dynamic Light Scattering (DLS) and transmission electron microscopy (TEM). The miRNAs differentially expressed in HCC were identified using The Cancer Genome Atlas (TCGA) database. The level of miR-135a-5p in patient tissue samples was detected by quantitative polymerase chain reaction. TargetScan and luciferase assay were used to predict and prove the target gene of miR-135a-5p. Finally, we identified the effects of miR-135a-5p on anti-apoptosis and the proliferation of HCC in the presence or absence of Dox using flow cytometry, Cell counting kit 8 (CCK-8) assay and western blot.RESULTSWe found that HBc increased the expression of exosomal miR-135a-5p. Integrated analysis of bioinformatics and patient samples found that miR-135a-5p was increased in HCC tissues in comparison with paracancerous tissues. Bioinformatic analysis and in vitro validation identified vesicle-associated membrane protein 2 (VAMP2) as a novel target gene of miR-135a-5p. Functional assays showed that exosomal miR-135a-5p induced apoptosis protection, cell proliferation, and chemotherapy resistance in HCC. In addition, the rescue experiment demonstrated that VAMP2 reversed apoptosis protection, cell growth, and drug resistance by miR-135a-5p. Finally, HBc promoted HCC anti-apoptosis, proliferation, and drug resistance and prevented Dox-induced apoptosis via the miR-135a-5p/VAMP2 axis.CONCLUSIONThese data suggested that HBc upregulated the expression of exosomal miR-135a-5p and promoted anti-apoptosis, cell proliferation, and chemical resistance through miR-135a-5p/VAMP2. Thus, our work indicated an essential role of the miR-135a-5p/VAMP2 regulatory axis in chemotherapy resistance of HCC and a potential molecular therapeutic target for HCC.

Biogenic synthesis of silver nanoparticles from leaf extract of Elettaria cardamomum and their antifungal activity against phytopathogens

The current study reports biogenic synthesis of silver nanoparticles from Elettaria cardamomum. Elettaria leaf extract was used as reducing and capping agent for nanoparticle synthesis from parent solution of silver nitrate. Nanoparticle suspension was characterized mainly using UV-Visible spectroscopy. Synthesis parameters namely, time, metal ion concentration, leaf extract quantity, reaction temperature and pH are well known to affect the final product of synthesis and hence, were varied to assess optimum conditions for synthesis. Nanoparticles synthesized at optimum conditions were washed and characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Nanoparticles obtained were in the size range of 5-80 nm (TEM), with an average particle size of 29.96 nm as calculated using Debye-Scherrer formula and average hydrodynamic diameter of 32.12 nm (DLS). FTIR implicates plausible role of protein part of leaf extract in nanoparticle synthesis and DLS confirms monodisperse nature of the suspension. Nanoparticle suspension was found to be stable after four months of storage at room temperature without the addition of any stabilizing agents. Silver nanoparticles exhibited excellent antifungal activity against various fungal phytopathogens with minimum inhibitory concentration as low as 8 µg/mL for Aspergillus niger, making them potential antifungal agents in the field of agriculture. Copyright © 2018 VBRI Press.

Amphiphilic methoxy poly(ethylene glycol)-b-poly(carbonate-selenide) with enhanced ROS responsiveness: Facile synthesis and oxidation process

The synthesis of ROS-responsive polymers has attracted much attentions in recent years. Herein, we report a series of amphiphilic methoxy poly(ethylene glycol)-b-poly(carbonate-selenide)s (mPEG45-b-poly(MSe)m, m = 12, 24, 36, 48, 60) by introducing selenide groups onto the backbone via one-pot lipase-catalyzed ring-opening polymerization (ROP), the synthesized amphiphilic polymers with enhanced ROS-responsiveness can self-assemble to form nanoparticles. Nuclear Magnetic Resonance (NMR), Gel Permeation Chromatography (GPC) and Fourier Transform Infrared (FTIR) are employed to confirm the structure of the polymers. Besides, the oxidation process of mPEG45-b-poly(MSe)m nanoparticles is also clarified. Ultraviolet–visible Spectrophotometer (UV–Vis), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) are further utilized to demonstrate the turbidity, morphology and size changes under oxidization, proving that the selenide groups endow the mPEG45-b-poly(MSe)m nanoparticles with enhanced ROS-response properties. Therefore, the above studies highlight the synthesized ROS-responsive polymers and provided a potential material for further applications.

Effect of carbon nanotubes on aging properties of hydrogenated nitrile rubber in the dilute oxygen medium

To solve the key problem of accelerated aging for packer rubber cylinder under high temperature. The hydrogenated nitrile rubber (HNBR) composites reinforced by multi-walled carbon nanotubes (MWCNTs) were prepared. Effect of MWCNTs on the aging performance of HNBR/MWCNTs composites was studied with dilute oxygen as a medium at 180 °C. Fourier-infrared spectroscopy, differential scanning calorimetry, dynamic thermomechanical analysis and transmission electron microscope were used to investigate the aging behavior of HNBR/MWCNTs composites. The tensile strength of HNBR composites with 3, 6, and 9 phr MWCNTs loading increased by 35%, 37%, and 39% respectively. After 15 days at 180 °C, HNBR composites with 3 phr of MWCNTs had a tensile strength retention rate of 91% and an elongation retention rate of 57%, while the blank HNBR composites had a tensile strength retention ratio of 72% and elongation retention ratio of 52%. The result of DSC shows that the presence of MWCNTs can enhance T g of HNBR composite, the T g increase rate (2 °C) for HNBR/MWCNTs composites was lower than that (3.2 °C) for the blank in 15 days at 180 °C. MWCNTs exhibited better reinforcement and excellent anti-aging performance. The possible anti-aging mechanism has been proposed.

Marine plant mediated green synthesis of silver nanoparticles using mangrove Rhizophora stylosa: Effect of variable process and their antibacterial activity

Background: Most natural plants used in the synthesis of silver nanoparticles are limited to marine plants. To carry out applications, colloidal silver nanoparticles (AgNps) should have appropriate properties such as homogeneous shapes, small and narrow particle size distribution, and long time stability. This study aims to determine the effects of a variable process of AgNps mediated mangrove Rhizophora stylosa (RS) leaf extract, and antibacterial activity.  Methods: Synthesis of AgNps was carried out by stirring silver nitrate solution with aqueous extract. The characterization of AgNps was carried out using UV-Vis spectrophotometry, X-ray diffraction (XRD), Dynamic Light Scattering (DLS) zetasizer and Transmission Electron Microscopy (TEM). Evaluation of antibacterial activity was carried out on Escherichia coli and Staphylococcus aureus. Reaction conditions such as the concentration of metal ions (0.001 M, 0.005 M, and 0.01 M), extracts (1%, 3%, and 5% v/v), and the reaction time on the size and stability of nanoparticles were also explored. Results: The UV-Vis spectroscopy showed an absorption of colloidal AgNps in a wavelength range of 403–443 nm.  TEM analysis showed that as-synthesized AgNps were spherical in shape with a size range of 5–87 nm. The use of 0.001 M and 0.005 M of Ag+ resulted in a smaller diameter than the synthesized AgNps, using 0.01 M Ag+, in the same extract concentration. The range of zeta potential was -24.9 mV to -27.7 mV. The as-synthesized AgNps were stable for more than one month. The XRD analysis showed four peaks, which were attributed to the face centered cubic crystal structure of metallic silver. The results of the silver nanoparticles synthesis showed good activity on Escherichia coli and Staphylococcus aureus, with an inhibition zone between 4.1–7.2 mm. Conclusions: The AgNps synthesized with RS leaf extract, which is a reducing agent, showed good potential as an antibacterial component.

Colorimetric Determination of Cu2+ by Glycine-Histidine Dipeptide Functionalized-Gold Nanoparticles

This study presents the development of a rapid and straightforward Cu2+ determination method through the interaction of glycine-histidine dipeptides with gold nanoparticles (AuNPs). Here, it was shown that AuNPs were clustered by the attachment of glycine-histidine dipeptides (GH) to the AuNPs. Accordingly, it was obtained from the Uv-vis spectrum that the max of the AuNPs dispersion at 520 nm showed a redshift to a higher energy region. This case was accelerated by adding Cu2+ ions to the medium, indicating an interaction between GH coated-AuNPs and Cu2+ ions, and the particles come together in a shorter time. This finding demonstrates that the developed-analytical method provides more selectivity to Cu2+ when testing in the presence of some other metal ions. The particles and aggregates' sizes were determined by Dynamic Light Scattering (DLS) measurement and Transmission Electron Microscopy (TEM) technique. The determination of Cu2+ in the tap water was also tested by spike using the developed method. In the light of the results obtained, it is thought that the developed analytical method can be quite advantageous for the rapid and selective determination of Cu2+ in water samples.