Formation Of Spherical Particles Research Articles

A putative amphipathic alpha helix in hepatitis B virus small envelope protein plays a critical role in the morphogenesis of subviral particles.

Hepatitis B virus (HBV) small (S) envelope protein has the intrinsic ability to direct the formation of small spherical subviral particles (SVPs) in eukaryotic cells. However, the molecular mechanism underlying the morphogenesis of SVPs from the monomeric S protein initially synthesized at the endoplasmic reticulum (ER) membrane remains largely elusive. Structure prediction and extensive mutagenesis analysis suggested that the amino acid residues spanning W156 to R169 of S protein form an amphipathic alpha helix and play essential roles in SVP production and S protein metabolic stability. Further biochemical analyses showed that the putative amphipathic alpha helix was not required for the disulfide-linked S protein oligomerization, but was essential for SVP morphogenesis. Pharmacological disruption of vesicle trafficking between the ER and Golgi complex in SVP producing cells supported the hypothesis that S protein-directed SVP morphogenesis takes place at the ER-Golgi intermediate compartment (ERGIC). Moreover, it was demonstrated that S protein is degraded in hepatocytes via a 20S proteasome-dependent, but ubiquitination-independent non-classic ER-associated degradation (ERAD) pathway. Taken together, the results reported herein favor a model in which the amphipathic alpha helix at the antigenic loop of S protein attaches to the lumen leaflet to facilitate SVP budding from the ERGIC compartment, whereas the failure of budding process may result in S protein degradation by 20S proteasome in an ubiquitination-independent manner.Importance Subviral particles are the predominant viral product produced by HBV-infected hepatocytes. Their levels exceed the virion particles by 10,000 to 100,000-fold in the blood of HBV infected individuals. The high levels of SVPs, or HBV surface antigen (HBsAg), in the circulation induces immune tolerance and contributes to the establishment of persistent HBV infection. The loss of HBsAg, often accompanied by appearance of anti-HBs antibodies, is the hallmark of durable immune control of HBV infection. Therapeutic induction of HBsAg loss is, therefore, considered to be essential for the restoration of host antiviral immune response and functional cure of chronic hepatitis B. Our findings on the mechanism of SVP morphogenesis and S protein metabolism will facilitate the rational discovery and development of antiviral drugs to achieve this therapeutic goal.

Preparation and In Vitro Cytotoxicity Assessments of Spherical Silica-Encapsulated Liposome Particles for Highly Efficient Drug Carriers.

This work reports the formation of spherical solid silica-encapsulated liposome particles (SLPs) as functions of the concentration of silica precursor, reaction time, temperature, and volume ratios of solvent, respectively. The solid SLPs are more robust and have better drug-loading-efficiency liquid liposomes in carrier formulations. The liquid-state liposomes are hard to handle and have a lower drug-loading efficiency because they are fragile to external stimuli and have narrow hydrophobic phospholipid bilayers. The SLPs were obtained by silicification with tetraethyl orthosilicate (TEOS) in the hydrophilic region of phospholipid bilayers by a sol-gel process. These SLPs were characterized by scanning electron microscopy (SEM), focused ion beam (FIB)-SEM, confocal laser scanning microscopy (CLSM), thermogravimetric analysis (TGA), ζ-potential, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and UV-vis spectroscopy. The obtained SLPs were spherical with an average size of 2-3 μm. The hydrophilic region of the SLP phospholipid bilayers was confirmed using CLSM with green fluorescent fluorescein isothiocyanate (FITC) labeling and FIB-SEM. Furthermore, the drug-loading capacity and in vitro cytotoxicity assessments were performed using several drug compounds and L929 cells. The drug-loading capacity of the SLPs was >95%, and in particular, the hydrophobic drug-loading capacity was 2.3 times higher than that of general liposomes. Moreover, the result of an in vitro cytotoxicity assessment of the SLPs was good, about 99% of cell viability.

THE USE OF PULSED VACUUM ARC PLASMA FOR THE SYNTHESIS OF HOLLOW SPHERICAL PARTICLES

A new method for obtaining metal coating, consisting of hollow spherical microparticles, is presented. The pulsed vacuum arc plasma is used as the medium for spraying copper and alumina cathodes and for particle deposition on a crystalline silicon substrate. The reason for the formation of hollow spherical particles is the agglomeration of nanoparticles falling on the surface from the plasma. The effects of the original surface geometry on the size of deposited particles were discussed. Another important result is the minimum time required for the coating of substrate. In our experiments, 5 min were enough to form a 20-μm coating layer.

Structural, photoluminescence, and photocatalytic properties of Mn and Eu co-doped ZnO nanoparticles

Abstract The solar driven-photocatalytic degradation using semiconductor nanoparticles (NPs) is an efficient approach to make wastewater free from organic pollutants. In this aspect, pristine ZnO NPs, Mn-doped ZnO NPs (Mn-ZnO NPs), and Mn, Eu co-doped ZnO nanoparticles (Mn-Eu-ZnO NPs) were synthesized by a soft chemical approach. XRD analysis confirmed the formation of a single-phase wurtzite structure without any additional phase impurity. TEM micrograph of Mn-Eu-ZnO NPs indicated the formation of spherical particles of size in the range of 8–15 nm. The photoluminescence spectra of Mn-Eu-ZnO NPs showed a broad defect band in the range of 400 to 750 nm suggesting its higher defect concentration as compared to ZnO NPs and Mn-ZnO NPs. The doped ZnO NPs exhibited higher photocatalytic degradation of Rhodamine B (RhB) under simulated solar light. Mn-Eu-ZnO, Mn-ZnO, and ZnO NPs showed complete photodegradation of RhB in 20, 40, and 90 min under simulated solar light, respectively. The enhanced photocatalytic degradation activity of Mn-Eu-ZnO NPs can be ascribed to the presence of higher defect concentration, enhanced optical absorption ability, high charge separation efficiency, and reduction in the recombination of photogenerated electron-hole pairs as well as their strong affinity for hydroxyl radical generation. Thus, the developed Mn-Eu-ZnO NPs can be used as potential photocatalyst for the degradation of organic dyes from wastewater.

Anti MRSA and Antiviral Evaluation of Nano Silver Against Avian Influenza virus

Preparation of nano sized silver particles was performed by using flower extract of Aerva javanica (AJ). Conversion of Ag+ ions to nanoscaled Ago was carried out in 90 min reaction by green approach. Antiviral potential of nanosilver (NS) was evaluated against Avian Influenza Virus (AIV) strain H9N2, in 9-11 days old chicken embryonated eggs. Synthesized particles were also screened against four methicillin-resistant Staphylococcus aureus (MRSA) strains by well diffusion method. Formation of spherical particles was confirmed by SPR band at 428 nm. XRD analysis confirmed face centred cubic crystal structure of particles with average particle size of 15 nm as calculated by Debye–Scherrer’s formula. Remarkable anti AIV activity was observed from NS particles with IC50 value 50 ?g/ml and this value is 200 times greater control drug i.e., Amantadine. Synthesized particles were also screened against four methicillin-resistant Staphylococcus aureus (MRSA) strains by well diffusion method. Significantly high antiviral and antibacterial activities were observed from nanosilver particles against AIV H9N2 and all four MRSA strains.Keywords:

Green synthesis of silver nanoparticles with phytosterols and betalain pigments as reducing agents present in cactus Myrtillocactus geometrizans.

Abstract

Stannates, titanates and tantalates modified with carbon and graphene quantum dots for enhancement of visible-light photocatalytic activity

Most efforts in heterogeneous photocatalysis are focused on development of new and stable photoactive materials efficient in degradation of various pollutants under visible-light irradiation. In this regard, the wide-bandgap perovskite semiconductors, i.e., SrTiO3 (titanate), SrSnO3 (stannate) and AgTaO3 (tantalate), were prepared by a solvothermal method, and then modified with carbon quantum dots (CQDs) or graphene quantum dots (GQDs) co-modified with erbium. The photocactivity was investigated for: (i) toluene degradation (gas phase), (ii) phenol decomposition (aqueous phase), and (iii) inactivation of Escherichia coli K12 bacteria. It has been found that the morphology of semiconductors depends on the synthesis conditions, resulting in the formation of spherical particles, rods and faceted particles for SrTiO3, SnSrO3 and AgTaO3, respectively. Additionally, deposition of CQDs and GQDs/erbium has resulted in an enhancement of light harvesting, thus improved photoactivity under visible-light irradiation. Samples modified with both erbium and GQDs revealed much higher photoactivity than corresponding pristine and CQDs-modified samples. Moreover, all photocatalyst modified with GQDs and Er exhibited a significant antibacterial properties under visible light irradiation (λ > 420 nm). Accordingly, it has been proposed that obtained semiconductors modified with QDs and Er are promising candidates as sustainable, clean and cheap materials for environmental purification under solar radiation.

Sterically Stabilized Polyionic Complex Nanogels of Chitosan Lysate and PEG-b-Polyglutamic Acid Copolymer for the Delivery of Irinotecan Active Metabolite (SN-38).

Poly Ionic Complex (PIC) nanogels are promising delivery systems with numerous attractions such as simple, fast, and organic solvent-free particle formation and mild drug loading conditions. Among polyelectrolytes, poly (L-amino acid) copolymers, such as poly (ethylene glycol)-block-poly (L-glutamic acid) copolymers (PEG-b-PGlu) are interesting biocompatible and biodegradable candidates bearing carboxylic acid functional groups. Aiming to solubilize and to preserve short-acting irinotecan active metabolite (SN38), sterically stabilized PIC nanogels were prepared through electrostatic charge neutralization between PEG-b-PGlu and chitosan lysate, a polycationic natural polymer obtained through digestion of chitosan by hydrogen peroxide oxidation and is soluble in a wide range of pH. Synthesis of PEG-b-PGlu was accomplished by N-carboxy anhydride polymerization of γ -benzyl L-glutamic acid, which is initiated by methoxy PEG-NH2 and successive debenzylation reaction. The resulting block copolymer was characterized by FTIR, 1H-NMR, and Size Exclusion Chromatography (SEC). Self-assembling properties of the PIC nanogels were investigated by pyrene assay, Dynamic Light Scattering (DLS), and Transmission Electron Microscopy (TEM), indicating the formation of homogeneous spherical particles with a mean size of 28 nm at the PEGb- PGlu concentrations/LMWC weight ratio of 5:1. Upon direct loading of SN38, the drug solubility enhanced more than 4×103 folds with a mean loading efficiency of 89% and the drug loading of 30%. PIC nanogels exhibited zeta potential of +1 mV, acceptable biocompatibility, and superior cytotoxicity in murine colorectal carcinoma (CT26 cell line) compared to free drug. In addition, the PIC nanogels provided SN38 protection against hydrolytic degradation in physiologic conditions. Conclusively, the well-tuned PIC nanogels are suggested as a potentially biocompatible nanocarrier for SN38 delivery.

Synthesis, Characterization, and Controlled Release Property Evaluation of Carboxymethyl Cellulose/Alginate (CMC/Alg) Encapsulated NPK Fertilizers

This work described the successful preparation of encapsulated nitrogen-phosphorus-potassium (NPK) fertilizers with the use of carboxymethyl cellulose/alginate (CMC/Alg) blend employing citric acid (CA) as the crosslinking agent. The study involved the preparation, characterization, release studies, and efficacy evaluation of the said fertilizer system. Fourier transform infrared (FTIR) and fluorescence spectroscopic methods, scanning electron microscopy (SEM), particle size analysis, and zeta potential measurements showed the successful formation of spherical particles with varying sizes (ranging from 733–1200 nm) via crosslinking. Release profiles of the CMC/Alg NPK conformed to the standards of controlled-release fertilizer with a maximum release rate of 50% for CMC/Alg NPK in 30 d. Investigation of the release mechanism using the Korsmeyer-Peppas mathematical model showed that the release of nutrients is governed by both coating material relaxation and diffusion processes. Controlled release behavior was demonstrated as confirmed in the efficacy evaluation of the prepared fertilizer in a 2-mo pot experiment using mung bean.

Formation of spherical Sn particles by reducing SnO2 film in floating wire-assisted H2/Ar plasma at atmospheric pressure

A green method to synthesize spherical Sn particles by reducing SnO2 film in atmospheric-pressure H2/Ar plasma at low temperatures for various applications is presented. The floating wire-assisted remotely-generated plasma with a mixture of 0.05% H2/Ar gas formed spherical metallic Sn particles by reducing a SnO2 layer on glass substrate. During the reduction process, H radical density was measured by using vacuum ultraviolet absorption spectroscopy, and plasma properties including electron density and gas temperature were diagnosed by optical emission spectroscopy. The inductively coupled generated plasma with a high electron density of 1014 cm−3, a hydrogen atom density of 1014 cm−3, and a gas temperature of 940 K was obtained at a remote region distance of 150 mm where the SnO2/glass substrate was placed for plasma treatment. The process has been modeled on the spherical Sn formation based on the reduction of SnO2 films using H radicals. Depending on the treatment condition, the total reduction area, where spherical Sn particles formed, was enlarged and could reach 300 mm2 after 2 min. The substrate temperature affected the expansion rate of the total reduction area and the growth of the Sn spheres.

Steric and Electronic Effects of Phosphane Additives on the Catalytic Performance of Colloidal Palladium Nanoparticles in the Semi‐Hydrogenation of Alkynes

AbstractWe report on the influence of phosphanes on the catalytic activity and selectivity of colloidal, tetraoctylammonium bromide (TOAB) stabilised palladium nanoparticles (NPs) in the semi‐hydrogenation of alkynes to olefins. Full characterisation of the catalytic system (HRTEM, EDX, XPS, IR, NMR) confirmed the formation of spherical particles with a narrow size distribution (1.9±0.5 nm). The catalytic performance of the Pd NPs in the semi‐hydrogenation of 1‐octyne, 2‐octyne and phenylacetylene to the respective olefins and the influences on the selectivity was investigated. The system shows high activities and selectivities at mild conditions (0 °C and 1.0 bar H2 pressure). It was shown that generally, phosphanes lead to an increase of both the reaction rate and selectivity towards the olefin where both steric and electronic effects of the ligand play a crucial role for the catalyst performance. A moderate steric demand of the ligand with a rather weak σ‐donating ability turned out to give the highest catalytic performance.

Electrochemical Properties of High Nickel Content Li(Ni0.7Co0.2Mn0.1)O₂ with an Alumina Thin-Coating Layer as a Cathode Material for Lithium Ion Batteries.

The cathode material, high Nickel content Ni0.7Co0.2Mn0.1 (NCM), was synthesized by coprecipitation with NH₄OH used as a complexing agent. The prepared materials are made in the formation of spherical particles of Li(Ni0.7Co0.2Mn0.1)O₂ of several micrometers in diameter. Al₂O₃ was coated by an impregnation method and its content was gradually increased to 1, 2 and 5 wt%. As a result, 1 wt% coated Al₂O₃ compared to pristine NCM exhibited 82% and 80% retention rates at 5 C and 1 wt% Al₂O₃ coated NCM recovery at 0.2 C after 5 C showed 100%. In addition, capacity retention of 1 wt% NCM+Al gently decreased in 100 cycle life characteristics, and capacity retention of 95% or more was confirmed.

Crystal Structure and Magnetic Properties of (Co-Ag) co-doped SnO2 Compounds

Pure SnO2, Sn0.94Co0.06O2, Sn0.91Co0.06Ag0.03O2, and Sn0.88Co0.06Ag0.06O2 compounds were synthesized by the solid-state reaction method. The structural characterization of these compounds by recording X-ray diffraction patterns (XRD) and analyzing them using Rietveld refinement analysis shows that these materials are in single-phase tetragonal rutile structure with typical lattice constant of a = b = 4.7385 A and c = 3.1871 A for SnO2 compound. SEM images show the formation of homogenous nanometer range spherical particles. Temperature variation of magnetization (M-T) measurements show a typical diamagnetic behavior in parent compound, while ferromagnetic (FM) to paramagnetic transition is observed in Sn0.94Co0.06O2 compound with a Curie temperature of 232.5 K. The (Co-Ag) co-doped SnO2 compounds undergo double ferromagnetic transitions. These compounds exhibit first FM transition below 620 K and another FM transition at 1108 K and 1052 K, respectively for Sn0.91Co0.06Ag0.03O2 and Sn0.88Co0.06Ag0.06O2 compounds. The measurement of magnetic hysteresis (M-H) curves at room temperature indicates the increase in coercivity and saturation magnetization values with the increase of (Co-Ag) co-doping concentration. The observed ferromagnetism was discussed based on the exchange interaction between Co2+ and Co3+ ions via oxygen vacancies.

Practical model for improved classification of trace chemical residues on surfaces in active spectroscopic measurements

Trace chemical detection and classification in stand-off reflection-based spectroscopic data is challenging due to the variability of measured data and the lack of physics-based models that can accurately predict spectra. Most available models assume that the chemical takes the form of spherical particles or uniform thin films. A more realistic chemical presentation that could be encountered is that of a nonuniform chemical film that is deposited after evaporation of the solvent that contained the chemical. We present an improved signature model for this type of solid film. The proposed model, called sparse transfer matrix, includes a log-normal distribution of film thicknesses and is found to reduce the root mean square error between simulated and measured data by about 25% when compared with either the particle or uniform thin film models. When applied to measured data, the sparse transfer matrix model provides a 10% to 28% increase in classification accuracy over traditional models.

In Vivo Genotoxicity Assessment of Gold Nanoparticles of Different Doses by Comet Assays

Gold nanoparticles were synthesis by green method using the soaked orange peels (citrus Sinensis) as reducing and stabilizing agent. The gold nanoparticles were diagnosed using the approved method, including the transmission electron microscope and the visible UV spectroscopy. Thus, the results of the diagnosis showed the formation of spherical particles with a size of 36 nanometers. Their biological effects on the bone marrow cells of albino mice were studied. Male albino mice were used in this study and randomly divided into seven groups. The first group was the control group injected with the physiological solution (Normal Saline) and the other six groups were injected with different doses of the solution of the gold nanoparticles (1, 2, 4, 6, 8 and 10) Mg/kg. The effect of gold nanoparticles on the DNA damage by bone marrow cells was studied using comet assay according to the following criteria: (DNA in Head%, Comet Length, Tail Length, DNA in Tail%, Olive Moment), the results showed a significant decrease (P?0.01) in the rate of DNA in Head%, while it showed a significant increase in Comet Length, Tail Length, DNA in Tail%, Olive Moment compared to the control group and all Doses studied. The effect of gold nanoparticles was directly proportional to the increase in the studied doses. The dose was 10 mg/kg, which was the highest toxicity, followed by the dose of 8 mg/kg, then the rest of the doses was descending.

Application of sol-gel methods to obtain silica materials decorated with ferrocenyl-ureidopyrimidine moieties. Preparation of hollow spheres and modification of a carbon electrode

The application of a sol-gel method, starting from N -(4-ferrocenyl-6-phenylpyrimidin-2-yl)- N ’-(3-(triethoxysilyl)prop-1-yl)-urea ( 4 ), tetraethoxysilane and a structure directing agent, led to the formation of hollow spherical particles with organic moieties concentrated on the inner surface. A similar sol-gel electrodeposition technique was used for the modification of the surface of a spectral graphite electrode. The solid materials were characterized by solid phase NMR and IR measurements, thermal analysis, SEM and TEM. The functional group attached to the ferrocene core offers the possibility to form H-bonds with various guest molecules that makes it a potential electrochemical sensor. • Ferrocene-containing hollow spheres were obtained by a sol-gel method in one step. • Organic moieties were shown to be concentrated on the inner surface . • Porous structure of shells was proved by TEM measurements . • Direct co-condensation was used to prepare a ferrocene functionalized electrode.

Effect of Al doping on the structural and optical properties of CuO nanoparticles prepared by solution combustion method: Experiment and DFT investigation

In this study, pure and Al doped CuO nanoparticles (NPs) has been synthesized using the solution combustion technique. The effect of the Al dopant on the structural, surface morphological, optical and electronic properties of the CuO NPs was studied. The crystalline structure of the NPs has been studied by X-ray diffraction (XRD) analysis. XRD studies indicate that the NPs produced are highly crystalline with tenorite phase. Al doping was found to modify the bond length, and lattice strain of the CuO NPs. The surface morphology of the NPs showed formation of spherical particles for lower Al doping while at higher doping concentration agglomeration of NPs occurs and the particle size changes. A reduction in the optical band gap of the NPs was observed due to Al doping and such a red shift in the band gap can be attributed to incorporation of the Al3+ ion doping effect. First principles calculations based on density functional theory (DFT) implemented in the VASP code was applied to study the electronic properties of pure and Al-doped CuO. The DFT study reveals that an impurity level is created within the energy gap of the NPs due to Al doping resulting in a reduction in the band gap, consistent with the experimental results.

Red emitting CaTiO3: Pr3+ nanophosphors for rapid identification of high contrast latent fingerprints

Red emitting (~612 nm) CaTiO3:Pr3+ long afterglow nanocrystals with a persistence time ~20 min (dark adapted human eyes) have been synthesised for developing high contrast latent fingerprints using the sol-gel process. Due to the persistent emission, CaTiO3:Pr3+ nanophosphor does not require a continuous source for excitation, thereby eliminating the background information even from multi-colour substrates, resulting in a high signal to noise ratio. As a consequence of which, minute features of level- I, II and III can be clearly studied in high contrast fingerprints. Considerable blue shift (~20 nm) was recorded in photoluminescence excitation due to the quantum confinement properties of CaTiO3:Pr3+ nanocrystals. Powder x-ray diffraction confirms the formation of a single phase orthorhombic structure of CaTiO3:Pr3+ with average crystallite size ~40 nm. Spectral parameters indicate a very high color purity of 99% with CIE coordinates (0.62, 0.37) which are very close to NTSC standards for an ideal red-emission. Transmission electron microscopy studies confirm the formation of spherical particles with narrow size distribution which makes them suitable to combine with fingerprint development methods such as powder dusting and cyanoacrylate fuming methods.

Preparation of silver nanoparticles using atmospheric discharge plasma for catalytic reduction of p-nitrophenol: the influence of pressure in the reactor

PurposeThis paper aims to synthesize silver nanoparticles using atmospheric discharge plasma in contact with liquid at different pressure in reactor and to assess their catalytical properties for reducing 4-nanoparticles (NP).Design/methodology/approachThe Ag colloidal NPs was rapidly synthesized as a result of non-equilibrium low-temperature plasma formation between an electrode and the surface of AgNO3 solution for 5 min at different pressure in reactor. Synthesized Ag NPs were characterized with common analytical techniques. Ultraviolet–visible (UV) spectroscopy, dynamic light scattering, scanning microcopy analysis were used to study the formation and characteristics of silver nanoparticles.FindingsThe formation of silver colloidal solutions under plasma discharge at different pressure in reactor is characterized by the presence of surface resonance peak in the spectra. Scanning electron microscope (SEM) images confirmed the formation of spherical particles having a size distribution in the range of 15-26 nm. The AgNPs solution showed excellent rapid catalytic activity for the complete degradation of toxic 4-nitrophenol (4-NPh) into non-toxic 4-aminophenol (4-APh) within 18 min.Research limitations/implicationsFurther studies are necessary for confirmation of the practical application, especially of deposition Ag NPs on TiO2.Practical implicationsThe method provides a simple and practical solution to improving the synthesis of colloidal solutions of Ag NPs for degradation of organic pollutants (4-NPh) in water and wasters water.Originality/valueAtmospheric discharge plasma in contact with liquid at different pressure can be used as an effective technique for synthesis of nanomaterials with catalytic properties.

In Situ Investigation of the Formation Kinematics of Plasma-Generated Silver Nanoparticles.

In this publication, it is shown how to synthesize silver nanoparticles from silver cations out of aqueous solutions by the use of an atmospheric pressure plasma source. The use of an atmospheric pressure plasma leads to a very fast reduction of silver ions in extensive solvent volumes. In order to investigate the nanoparticle synthesis process, ultraviolet/visible (UV/VIS) absorption spectra were recorded in situ. By using transmission electron microscopy and by the analysis of UV/VIS spectra, the kinetics of silver nanoparticle formation by plasma influence can be seen in more detail. For example, there are two different sections visible in the synthesis during the plasma exposure process. The first section of the synthesis is characterized by a linear formation of small spherical particles of nearly constant size. The second section is predominated by saturation effects. Here, particle faults are increasingly formed, induced by changes in the particle shape and the fusion of those particles. The plasma exposure time, therefore, determines the shape and size distribution of the nanoparticles.