Microsphere Particles Research Articles

Formation of microspherical particles of albumin with model drug using spray drying process

Spray drying method enables to produce microspherical particles with narrow size distribution. Production of such microparticles is relevant for the development of the advanced systems for inhalation delivery of drugs. The aerosol particles diameter must be between 1 and 3 μm. Composite microparticles based on bovine serum albumin and model drug phenacetin were produced in the present work using the spray-drying method. The absence of a crystalline phase of the drug in composite microparticles was verified using several physicochemical methods. The average radius of the produced microparticles was found to be 1 μm based on the results from scanning electron microscopy. The rate of the dissolution of the drug included in microparticles is faster than that of crystalline phenacetin. The obtained results can be used for the development of the method for preparation of composite microparticles based on protein molecules using the spray-drying technique.

Hydrochar-derived fuels from waste walnut shell through hydrothermal carbonization: characterization and effect of processing parameters

The raw walnut shell was converted to hydrochar fuel through hydrothermal carbonization. The structural, morphological, and compositional analyses were carried out using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric and basic elemental analyses. The effect of the processing parameters including reaction temperature, residence time, and water:biomass ratio on the hydrothermal treatment was studied. The selected hydrochar has been produced at the optimized condition of T = 250 °C, t = 5 h, and water:biomass ratio = 6.0 mL/g. The H:C and O:C atomic ratios decreased from 1.51 and 0.73 to 0.91 and 0.26 for walnut shell and the selected hydrochar, respectively. The elemental reduction occurred through the carbonization process, which mainly includes dehydration, decarboxylation, and depolymerization reactions in liquid phase. The higher heating value increased from 18.85 for walnut shell to 27.95 for the selected hydrochar. The obtained walnut shell–based hydrochar presents a relatively homogenized structure consisting of microspherical particles with a mean diameter of 6 μm. This lignin-like material with high carbon content and low ash content shows high thermal stability. These promising results are relevant to the development of hydrochar products from waste biomass for fuel applications.

Compact graphene powders with high volumetric capacitance: Microspherical assembly of graphene via surface modification using cyanamide

Graphene has received increasing attention as an electrode material for electrical double-layer capacitors (EDLCs) due to its high specific surface area and high intrinsic electrical conductivity. Recently, there have been tremendous achievements for improving the gravimetric capacitance of graphene. However, graphene’s low density limits its practical applications as electrode material for EDLCs because of the unacceptably poor volumetric capacitance. To take full advantage of graphene’s superior properties, it preferably needs to be assembled into microspherical powder form with low ion transport resistance as well as high packing density. Herein, we demonstrate novel spray-drying strategy for the facile and scalable assembly of graphene into a compact microspherical powder via surface modification using cyanamide, which plays very important roles in the assembly process: preventing graphene oxide from interacting with water and restacking, polymerization into graphitic carbon nitride, and its thermal decomposition. The key challenges are the assembly of graphene in the form of microspherical particles, the densification of graphene microspheres with a high packing density and compressive strength, and the generation of mesopores in the graphene microspheres. Notably, N doped graphene microspheres exhibit an outstanding volumetric capacitance (259 F cm−3 at 0.1 A g−1) in 1 M tetraethylammonium tetrafluoroborate (TEABF4)/acetonitrile (ACN) electrolyte with excellent cycle stability (93.8% of the initial capacitance after 100,000 cycles at 2 A g−1). The graphene microspheres exhibit an excellent rate capability with a time constant of 0.92 s owing to the favorable formation of mesopores.

Evaluation of the hydrophobic properties of latex microspheres and Bacillus spores. Influence of the particle size on the data obtained by the MATH method (microbial adhesion to hydrocarbons)

The current experimental study investigates the influence of latex microsphere particles' size on the assessment of their hydrophilic/hydrophobic character, using the method known as “Microbial Adhesion to Hydrocarbons” (MATH). Since bacteria surfaces often change according to the environment in which they find themselves, most of the experiments here were carried out using the calibrated latex microspheres Polybeads® and Yellow-green Fluoresbrite® (Polyscience) microspheres with diameters between 0.2 μm and 4.5 μm. All the beads had a density of ˜1.05 g/cm3. The first set of experiments was performed to adapt the procedure for measurements of water contact angles to microsphere lawns. It was found that all the microspheres tested were hydrophobic, when using a water contact angle of around 110-118°. However, wide differences were observed using the MATH method. The smaller microspheres (0.2 μm, 0.5 μm +/- 0.75 μm) exhibited a poor affinity to hexadecane, even after long contact times, suggesting a hydrophilic character. In contrast, larger microspheres quickly adhered to hexadecane, which is consistent with the values obtained for the water contact angles observed. These results suggest that, at least where hydrophobic particles are concerned, the MATH method is not suitable for the assessment of the hydrophobic character of particles with diameters of less than 1.0 μm. We lastly investigated whether the data obtained for Bacillus spores could also be affected by spore size. The hydrophobicity of spores of eight Bacillus strains was analysed by both MATH and contact angle. Some discrepancies were observed between both methods but could not be related their size (length or width).

Hierarchical mesoporous silica microspheres as unique hard-template for preparation of hierarchical mesoporous TiO2 microspheres with trimodal mesoporosities via nanocasting

Abstract This work for the first time reported that hierarchical meso-mesoporous SBA-15 silica microspheres (HMM-SiO 2 -MSs) can serve as a unique and suitable hard-template for the nanocasting preparation of mesoporous TiO 2 with both hierarchical mesostructures and well-preserved microsphere particle morphology. A two-step impregnation (TSI) method was developed and customized and its effectiveness was studied in comparison with the single-step impregnation method. Trimodal mesoporosities and their origin are newly recognized and analyzed. The materials were examined by various techniques, including the FE-SEM, N 2 sorption, TEM and XRD. Under optimized conditions, the hierarchical mesostructures and spherical particle morphology of HMM-SiO 2 -MSs can be replicated for HMM-TiO 2 -MSs. The high surface area and pore volume of HMM-TiO 2 -MSs reach 194 m 2 g -1 and 0.68 cm 3 g -1 , respectively, with the latter more than twice those templated by conventional SBA-15s. Besides HMM-TiO 2 -MSs, such HMM-SiO 2 -MSs as hard-template might be extended to the preparation of other materials with hierarchical mesostructures.

Preparation of Hyaluronic‐Acid‐Based Microspherical Particles with Tunable Morphology Using a Spray Method on a Superhydrophobic Surface

AbstractHyaluronic acid (HA) gel microspheres have advantages in the application of hydrogel injections due to their uniform size and shape. The HA microspheres are typically prepared using oil‐emulsion methods, which often use toxic solvents, or spray methods involving dehydration, which can negatively affect the properties of the hydrogel. In this study, an alternative fabrication method that avoids the use of solvents or dehydration is introduced. A poly‐dimethylsiloxane template is micro‐patterned to mimic the papillae structure of the lotus leaf which has superhydrophobicity. Glycidyl‐methacrylate HA solution is sprayed on the superhydrophobic template followed by photocrosslinking the droplet to produce spherical shapes of HA hydrogel particles. Gel particles with diverse shapes are formed, with the shapes depending on the arrangement of the papillae and surface hydrophobicity. As a result, microspherical particles with aspect ratios greater than 0.8 are produced.

Z-scheme water splitting by microspherical Rh-doped SrTiO3 photocatalysts prepared by a spray drying method

Microspherical particles of Rh-doped SrTiO3 (SrTiO3:Rh) having size of 1–2 μm were synthesized by a spray drying (SD) method employing a water-soluble ammonium trilactatotitanate. When the calcination temperature increased up to 1200 °C, primary particles grew significantly while the microspherical morphology of the secondary particles was kept. Dynamic light scattering analysis proved well-dispersive nature of the SD sample. Photocatalytic activities of SrTiO3:Rh synthesized by the SD method, solid state reaction (SSR), and a polymerizable complex (PC) method were evaluated for H2 evolution using an electron donor such as methanol, Fe2+, or [Co(bpy)3]2+ and Z-scheme water splitting combined with BiVO4 of an O2-evolving photocatalyst and either Fe3+/2+, [Co(bpy)3]3+/2+, or reduced graphene oxide as an electron mediator. SrTiO3:Rh prepared by the SD method showed much higher activities for all Z-scheme water splitting than the samples synthesized by the SSR method. Activities of the SD sample for Z-scheme water splitting using electron shuttles, Fe3+/2+ and [Co(bpy)3]3+/2+, were slightly higher or comparable to those of the PC sample whereas the SD sample achieved higher activity in Z-scheme water splitting based on interparticle electron transfer. In addition, even when the mass of SrTiO3:Rh used for the Z-scheme system with Fe3+/2+ was decreased from 50 mg to 30 mg, the SD sample still showed high activity while the activity decreased for the SSR and PC samples. Thus, usefulness of the SD method to obtain highly active SrTiO3:Rh with well-dispersive nature has been demonstrated.

Study on a Polymer Profile Control Agent with Controllable Swelling Time

The study provided a microsphere profile control agent, which can smoothly go deep into the stratum by using the hydrophobic shell structure as the “protective film”. While the solution time in simulated brine was prolonged, water molecules went deep into the inside of the microsphere particles through the pore structure, and combined with hydrophilic groups. Because of the combination, the microsphere polymer started to swell, and opened the shell into long chain for days, and then at the end, its hydrophilic-hydrophobic block groups were all exposed in the solution, which resulted in self-thickening property. The dissolution time after entering into the stratum, i.e. the shell “rupture” time can be controlled by adjusting the carbon chains length of hydrophobic groups in the synthetic process. The agent can not only prolong the depth of plugging and provide a stable plugging rate, but also enlarge the water swept volume after dissolution. This method can stabilize the oil production and control the water cut. The function of delayed thickening ability makes the stratum sealed but kept at a certain permeability.

Bioluminescent aptamer-based solid-phase microassay to detect lung tumor cells in plasma

Two high-affinity DNA aptamers for lung tumor cells were applied as biospecific elements in bioluminescent assay of patient blood. The oligonucleotide complementary to the 5′ end of both aptamers carrying either biotin or Ca2+-regulated photoprotein obelin was used to form a sandwich-type analytical complex on the surfaces of magnetic streptavidin-activated microspherical particles. Clinical blood samples from cases of morphologically confirmed lung cancer and control samples were analyzed applying the developed assay. From the receiver operator curve (ROC) analysis, the chosen threshold value as clinical decision limit offers the sensitivity of 91.5% and the specificity of 75% (p < 0.001). The area under ROC curve with the value of 0.901 distinguishes well between the two groups under investigation.

RNA‐Capturing Microsphere Particles (R‐CAMPs) for Optimization of Functional Aptamers

RNA aptamers are useful building blocks for constructing functional nucleic acid-based nanoarchitectures. The abilities of aptamers to recognize specific ligands have also been utilized for various biotechnological applications. Solution conditions, which can differ depending on the application, impact the affinity of the aptamers, and thus it is important to optimize the aptamers for the solution conditions to be employed. To simplify the aptamer optimization process, an efficient method that enables re-selection of an aptamer from a partially randomized library is developed. The process relies on RNA-capturing microsphere particles (R-CAMPs): each particle displays different clones of identical DNA and RNA sequences. Using a fluorescence-activated cell sorter, the R-CAMPs that are linked to functional aptamers are sorted. It is demonstrated that after a single round of reselection, several functional aptamers, including the wild-type, are selected from a library of 16 384 sequences. The selection using R-CAMPs is further performed under the solution containing high concentration of ethylene glycol, suggesting applicability in various conditions to optimize an aptamer for a particular application. As any type of RNA clone can be displayed on the microspheres, the technology demonstrated here will be useful for the selection of RNAs based on diverse functions.

Synthesis of magnetically controlled Fe3O4 composites and their enhanced microwave absorption properties

In this work, a new concept of dynamic granular arrays was proposed based on magnetically controlled particles. Method of external rotating magnetic field (ERMF), based on a dipole interaction of magnetic spherical Fe3O4 particles in highly ordered volume arrays is proposed and a design for its practical implementation is developed. The paper also presents a method for the formation of flat microspherical particles arrays using a dipole magnetic field of a given geometric shape. Reflection spectra of electromagnetic radiation from a volume dense packed array of Fe3O4 particles with thicknesses of 3 and 6 mm, and a flat particles array with a set of 15 and 30 layers, as well as frequency characteristics of attenuation of electromagnetic radiation of the claimed materials in the frequency range from 8 to 12.5 GHz obtained. Presented method and the installation have the prospect of being used in the processes of making composite materials for electromagnetic radiation protection using a wide range of materials of micro and nanoparticles.

Elaboration of aluminum-based ultralight material technology

Abstract The possibility of receiving preparations from the aluminum alloy strengthened by input of particles of adamant and hollow silica-alumina microspheres is investigated. For the purpose of increase in adhesion of a melt to a surface of microspheres, experiments were made, both with classical microspheres, and with microspheres the surface of which was modified by the covering containing chrome and carbide of chrome. Influence of adhesion on mechanical characteristics and increase in firmness to the exemplars sated with spheres at test according to the scheme the crossed cylinders with a counterbody of steel 40× is shown.

Investigation of the dielectric and thermal conductive properties of core–shell structured HGM@hBN/PTFE composites

Porous polymer materials have been widely used for the preparation of low dielectric constant materials, but they also suffer from high moisture absorption and decreased thermal conductivity. In this study, core–shell structured hexagonal boron nitride coated hollow glass microsphere (HGM@hBN) particles were prepared using an electrostatic-assembly process and incorporated into poly(tetrafluoroethylene) (PTFE). The composites exhibited decreased dielectric constants due to the implantation of air, which is mainly encapsulated in HGM. The hBN layer on the surface of HGM effectively enhanced composite thermal conductivity due to its special core-shell form. The 30 vol% HGM@hBN/PTFE composites had a low dielectric constant of 1.68, low moisture absorption of 0.11%, and thermal conductivity (0.276 W/mK) was improved by 43% compared with that of 30 vol% HGM/PTFE composites. This study provides a facile and cost-effective strategy for fabricating polymer composites with low dielectric constant, low moisture absorption and no deteriorated thermal conductivity simultaneously.

Lysozyme-Based Composite Drug Preparations for Inhalation Administration

Inhalation delivery is a promising route for drug administration. The particles of drug aerosol must have a diameter between 1 and 3 μm. The use of microspherical particles based on protein matrix allows for enhanced bioavailability of poorly water-soluble drugs and improved biocompatibility. In the present work, spray drying method was employed for the preparation of the microspherical particles of lysozyme with a model drug compound phenacetin. The average aerodynamic radius of the prepared particle is 1 μm. We show that the spray drying regime produces microparticles with low residual solvent content. The release time of phenacetin from the microspherical particles is much lower than that of the pure drug. These results allow developing a strategy for the production of the protein matrix-based systems for the inhalation delivery of poorly water-soluble drugs.

Controllable morphology, size and inner structure of Ru particles prepared by spray-pyrolysis

Micro-spherical Ru particles with varied Brunauer-Emmett-Teller (BET) surface area (from 0.2 m2/g to 56 m2/g) were synthesized from (NH4)2RuCl6 solution visa spray-pyrolysis methods. The morphology and size of as-synthesized Ru particles were controlled by the dry spraying treatment, while the inner structure of Ru particles was adjusted by the sintering process. The influences of sintered temperature on the inner structure of Ru particles were investigated. The microstructural transformation mechanisms of spray dried (NH4)2RuCl6 particles during thermal decomposition were revealed. The as-synthesized Ru powder with low BET surface area (0.1963 m2/g) shows good sintering property, while the Ru powder with high BET surface area (56.2313 m2/g) shows excellent sulfur capacity. The powder technology can be applied to regulate the morphology, size and inner structure of particles.

High volumetric energy density of LiFePO4/C microspheres based on xylitol-polyvinyl alcohol complex carbon sources

High volumetric energy density LiFePO4/C electrode was synthesized by wet ball-milling, spray drying and carbothermal reduction using xylitol-polyvinyl alcohol (PVA) as complex carbon sources. The fused xylitol with certain viscosity is readily coated on the surface of ferric phosphate (FePO4) during ball milling. PVA hydrogel not only forms a film on the surface of FePO4, which fixes the coating of xylitol to form a gel network, but also acts as a dispersing agent to make the precursor particles disperse more uniformly. The unique properties of the complex carbon sources result in a homogenous carbon-coating all over the primary submicron LiFePO4 particles (100–200 nm in diameter) to form a core-shell structure, and the regular microsphere particles (2–10 μm in diameter) are composed of the primary particles connected by a gel-conductive carbon network. This unique structure provides a Li+ diffusion channel and improves the electronic conductivity. The synthesized LiFePO4/C exhibits high electronic conductivity (2 × 10−1 S cm−1) and high tap density (1.6 g cm−3) with excellent electrochemical performance (at room and low temperatures) and high volumetric energy density (617.8 Wh L−1 at 10 C rate).

Convenient and Template-Free Route to One-Pot Green Synthesis of Polyrhodanine Core–Shell Nanoparticles

In this publication, a copper acetate-mediated rhodanine polymerization reaction is examined. It is demonstrated that at room temperature, Cu(II) acetate complexes with rhodanine generate solid nanospheres, which, upon heating in a microwave, results in polyrhodanine core–shell nano- and microsphere particles. The structural analysis of the polyrhodanine nanosphere produced by this efficient microwave-initiated method was conducted by Fourier transform infrared spectroscopy, UV–vis spectroscopy, scanning electron microscopy, and transmission electron microscopy. In addition, it is verified that this template-free, efficient, and versatile synthesis of polyrhodanine nanospheres can also be accomplished by introducing a strong oxidant KMnO4 as a cocatalyst with copper acetate without compromising the morphology of the resulting core–shell nanospheres. It is also demonstrated that the polyrhodanine nanospheres can be used to adsorb methyl orange dye, a known contaminant in industrial wastewater.

Synthesis and characterization of micro-spherical tungsten-molybdenum alloy particles using spray drying combined with microwave assisted calcination process

Tungsten‑molybdenum (W-Mo) alloy is widely used as high temperature materials. In this study, well-dispersed micro-spherical W-Mo alloy (in any Mo equivalent) particles were achieved by spray drying combined with two-step microwave assistant calcination from commercial (NH4)10W12O41 and (NH4)6Mo7O24. The morphology and size of as-synthesized W-Mo alloy particles were controlled by spray drying treatment. The influences of calcined temperature in the microwave assistant calcination on the phase, morphology and size of W-Mo particles were investigated. The size distribution of as-prepared W-Mo alloys particles was between 1 and 8 μm, and the average size was about 3 μm. The as-synthesized W-Mo alloy powder shows good sintering property. It should be noted that the powder technology in this study can be applied to synthesize other alloys powders (binary, ternary and more) with high-performance requirements.

Gel foam or microsphere particles for partial splenic artery embolization in managing patients with hypersplenism

Background and aim of studySpleen is the largest lymphoid organ on the human body, it has a very important immunological functions. Portal hypertension accompanied liver cirrhosis commonly leads to splenomegaly which may be complicated by hypersplenism. Also liver cirrhosis is frequently associated with decreased hematological indices with subsequent anemia, thrombocytopenia and leucopenia. Spontaneous bleeding can delay any surgical or endovascular intervention. Leucopenia with decreased immunity may interfere with treatment of cancer patients using chemotherapy. The objective of this prospective study is to achieve the maximum splenic tissue infarction with the least possible complications by performing partial splenic artery embolization in cases of hypersplenism through comparing two materials; gel foam in one group and microspheres in another group. Patients and methodsThe study was conducted from October 2014 to September 2015. Thirty patients included in this study were presented by hypersplenism. They were 14 males and 16 females with mean age of 51 years. All patients were subjected to full history taking, clinical examination, laboratory investigations, pelvi-abdominal US and interventional procedure (transcatheter partial splenic artery embolization). The patients were divided into two groups, group (1): Fifteen patients were subjected to partial splenic embolization (PSE) using gel foam, group (2): Fifteen patients were subjected to partial splenic embolization (PSE) using microspheres. ResultsMultiple complications appeared after the procedure some of them were of minor importance as post embolization syndrome (fever, pain and nausea) that continued for two days and disappeared in five patients. Haematemesis occurred in one patient of the first group. One case in the first group showed abscess formation after the procedure and this patient underwent the procedure using gel foam particles, four cases showed portal vein thrombosis, two in each group, Pleural effusion appeared in two patients of first group. Regarding the efficacy of the procedure, improvement in laboratory tests were nearly the same in both groups. However, regarding the occurrence of serious complications, the microsphere particles group show fewer complications than gel foam group. ConclusionPSE using gel foam or microsphere showed nearly the same efficacy with no significant difference between the improvement in laboratory tests. However, using microsphere particles was associated with fewer occurrences of serious complications when compared with using gel foam.

Dandelion-Like Microspherical MCM-22 Zeolite Using BP 2000 as a Hard Template.

The chemistry between layered MWW zeolite and carbon black pearls (BP 2000) as an inexpensive hard template was investigated to develop a rational one-pot synthesis of MCM-22 microspheres. The characterization results showed that the insertion of BP 2000 in the gel synthesis did not substantially compromise the crystallinity and microporosity, and the microscopic analyses showed that BP 2000 played a key role in controlling the final morphology of the MCM-22 zeolite, creating beautiful dandelion-like microspherical particles. The morphology obtained is due to the tortuous shape of the hard template, the particular MWW particle crystals, the interaction with the external surface of the MWW zeolitic precursor, and the synthesis conditions. The stacking of MWW crystals with edge-to-face orientations generates meso-/macrovoids, allowing access to the interiors of the microspheres. The microspheres were homogeneous with sizes ranging from 6 to 8 μm with an increase of the external surface and a macroporous size distribution centered at 200 nm, which is two times that of the traditional MCM-22 zeolite.