Powder Microspheres Research Articles

Nanocrystal-chitosan particles for intra-articular delivery of disease-modifying osteoarthritis drugs

Osteoarthritis is the most common chronic joint disease and a major health care concern due to the lack of efficient treatments. This is mainly related to the local and degenerative nature of this disease. Kartogenin was recently reported as a disease-modifying osteoarthritis drug that promotes cartilage repair, but its therapeutic effect is impeded by its very low solubility. Therefore, we designed a unique nanocrystal-chitosan particle intra-articular delivery system for osteoarthritis treatment that merges the following formulation techniques: nanosize reduction of a drug by wet milling and spray drying. The intermediate formulation (kartogenin nanocrystals) increased the solubility and dissolution rates of kartogenin. The final drug delivery system consisted of an easily resuspendable and ready-to-use microsphere powder for intra-articular injection. Positively charged chitosan microspheres with a median size of approximately 10 µm acted as a mothership drug delivery system for kartogenin nanocrystals in a simulated intra-articular injection. The microspheres showed suitable stability and a controlled release profile in synovial fluid and were nontoxic in human synoviocytes. The cartilage retention skills of the microspheres were also explored ex vivo using cartilage. This drug delivery system shows promise for advancement to preclinical stages in osteoarthritis therapy and scale-up production.

Efficient preparation of single-sided structural color fabrics with asymmetric wettability, angle-dependence and patternability based on liquid photonic crystals

Liquid photonic crystals (LPCs) with structural colors have become the most promising materials for preparing structural color fabrics, which have received extensive attention in textile printing and dyeing. However, the tedious and uncontrollable preparation process for LPCs and its expensive equipment for structural color fabrics with asymmetric wettability limit the practical application of structural color materials. Herein, inspired by the Janus wettability of the unidirectional moisture transport fabric, a simple and efficient approach is reported to fabricate single-sided structural color fabrics (SSCFs) with asymmetric wettability and angle dependence. To obtain asymmetrically wetted substrate fabrics, a low-cost, high-temperature assisted spraying strategy is used to build a hydrophobic layer on one side of the fabric. The ready-to-use LPCs with target mass fraction are accurately prepared by re-dispersing the dry poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)) microsphere powder and are uniformly scraped onto the hydrophilic side of the fabric to prepare SSCFs. The as-prepared samples show a brilliant and iridescent structural color, and their color is adjusted by varying the size of the P(St-MMA-AA) microspheres. The water contact angle of the front side (with structural colors) of SSCFs treated by sintering and water bath is 37°, which facilitates further encapsulation to improve the color fastness of SSCFs. Meanwhile, the photonic crystals on the fabric remain ordered. This work provides an alternative, low-cost and practical preparation scheme for the structural coloring of textiles based on LPCs.

CVD growth of the centimeter-scale continuous 2D MoS2 film by modulating the release of Mo vapor with adjusting the particle size of Al2O3 microsphere

We report a convenient chemical vapor deposition (CVD) strategy of two-dimensional (2D) MoS2: the release of Mo vapor is modulated by adjusting the particle size of Al2O3 microsphere powder which uniformly cover on MoO3 precursor, so as to achieve controllable synthesis of MoS2. In this CVD system, Al2O3 is inactive, and the particle size of Al2O3 microsphere is the key parameter of affecting the release amount of Mo vapor. When the particle size of Al2O3 microsphere is 100 nm, a centimeter-scale continuous monolayer MoS2 can be obtained. This work provides a feasible approach to controllably synthesize 2D transition metal dichalcogenides (TMDCs).

Synthesis of nanograined zirconium diboride microsphere powder feedstock via emulsification of suspensions

Ceramic nanograined materials have desirable characteristics compared to their macroparticle counterparts but are rarely used in industrial applications due to issues with poor handleability and health hazards. Due to interparticle forces that become more dominant as the particle size decreases, it is difficult to use nanomaterials to fill dies, spread on surfaces, or flow through hoppers found in various manufacturing processes. Here we report a scalable gelcasting solution and unique emulsification process to create microspheres composed of nanoscale powders to enhance the flowability and handleability of nanomaterials. The gelcasting solution and emulsification process can be used with any nanoparticle composition that can be suspended in a liquid phase. This paper reports the effects of various parameters on zirconium diboride microsphere formation, such as surfactant content and mixing conditions. The microspheres maintain the nano-scale characteristics of the powder but improve its flowability by using cross-linked polyvinyl alcohol to combine irregularly shaped zirconium diboride nanoparticles with a particle diameter of 60 nm into larger spherical particles with a d50∼25 μm. This hierarchical feedstock engineering design combine the positive characteristics of materials across both length scales and improve the flowability of the feedstock from a Hausner Ratio of 1.56 to 1.19. The materials produced using this technique can be used in thermal plasma spray, die filling for hot pressing or spark plasma sintering, and binder jet printing applications.

Utilization of fly ash microsphere powder as a mineral admixture of cement: Effects on early hydration and microstructure at different curing temperatures

Fly ash microsphere (FAM), a high value-added by-product, are powdered hollow beads separated from fly ash in power plants. This paper investigated the effects of FAM as a mineral admixture on the 3 d hydration and microstructure of cement. A composite binder containing inert quartz powder with a surface area similar to that of FAM was selected as the control sample. The results show that FAM has a low reaction degree at room temperature because FAM mainly exerts physical effects, and almost no pozzolanic reactions occur. However, increasing the curing temperature can significantly activate the pozzolanic activity of FAM and increase the reaction degree by up to 20% at 3 d. The reaction of FAM reduces the macropore volume, leading to a denser microstructure due to the pozzolanic reaction. Therefore, increasing the curing temperatures decreases the gap of the compressive strength between the paste containing FAM and the cement paste.

Spray-Drying Synthesis of MOFs, COFs, and Related Composites.

ConspectusMetal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are among the most attractive porous materials today. They exhibit outstanding porosity for countless applications such as gas storage, CO2 capture, gas separation, sensing, drug delivery, and catalysis. Moreover, researchers have recently begun to combine MOFs or COFs with other functional materials to obtain composites that boast the respective strengths, and mitigate the respective weaknesses, of each component, enabling enhanced performance in many of the aforementioned applications. Accordingly, development of methods for fabrication of MOFs, COFs, and related composites is important for facilitating adoption of these materials in industry. One promising synthetic technique is spray-drying, which is already well-integrated in manufacturing processes for diverse sectors. It enables rapid, continuous and scalable production of dry microspherical powders in a single step, leading to lower fabrication costs and shorter production times compared to traditional methods.In this Account, we outline our ongoing work on spray-drying synthesis of crystalline porous MOFs, COFs, and related composites. Versatile and tunable, spray-drying can be adapted to perform reactions involving coordination and covalent chemistry for the synthesis of micrometer spherical beads/superstructures of MOFs and COFs. Likewise, MOF- and COF-based composites can be synthesized using similar conditions as those for pure MOFs or COFs, through the simple introduction of additional functional materials into the feed precursor solution or colloid. Interestingly, spray-drying can also be done in water, thus providing the basis for its use as a scalable green method for industrial fabrication of these materials. To date, spray-drying has already been scaled up for pilot production (kilogram scale) of MOFs.

Submicronic nanostructured spherical zirconium-cerium powders for products of an orthopedic stomatology

The method of the ultrasonic spraying pyrolysis (USP) synthesized submicronic ceramic powders of structure of ZrO2+12 mol.%CeO2 intended for the subsequent manufacture on their basis of ceramic implants in an orthopedic stomatology. It is shown that (URP) allows to receive microspherical powders of zirconium-cerium ceramics, the multiparticle agglomerates having narrow dispersion and not forming in itself difficult the separable. The exemplars baked from new aerosol powders on the level of mechanical characteristics are close similar to characteristics for the ceramics manufactured of ultradispersed powders.

The Optical Properties of Polydisperse Glass Microsphere Ensembles in the Infrared Spectral Region

Semitransparent composites with glass microspheres are promising modern materials. In particular, they contribute to the increase of the efficiency of heat-insulating coatings. An experimental study of the transmission and scattering of infrared radiation (at wavelengths from 2 to 25 μm) by a sodium borosilicate glass microsphere powder is presented. The spectra, angular-scattering patterns, and the degree of polarization of scattered radiation were studied.

Optical and biological properties of transparent nanocrystalline hydroxyapatite obtained through spark plasma sintering

Transparent bioceramics have attracted a large amount of research interest as they facilitate direct observation of biointerfacial reactions. Thus far, attempts to achieve transparent hydroxyapatite have been focused on augmenting the sintering pressure and/or extending the sintering duration. This study aims at fabricating transparent HA using a direct and fast spark plasma sintering process with appropriate starting powder and moderate sintering pressure. Three types of raw powder, namely micro-spheres, nano-rods and nano-spheres, were sintered to investigate the optical and biological properties of the compacted pellets. It was found that in terms of transparency, the micro-sphere pellet sintered at 1000°C stood out with an in-line transmittance as high as 84% achieved at 1300nm for a 2mm thick sample. In addition, pellets fabricated from micro-spheres demonstrated the highest cell viability in in vitro biological tests with L929 cells. Living cells cultured on a transparent micro-sphere pellet could be directly and clearly observed by light microscopy. It is thus concluded that the micro-sphere powder is the most desirable raw material to manufacture transparent hydroxyapatite because it could enable dense pellets with notably high transparency and outstanding in vitro biocompatibility to be readily obtained.

Double Step Sintering Behavior Of 316L Nanoparticle Dispersed Micro-Sphere Powder

Abstract 316L stainless steel is a well-established engineering material and lots of components are fabricated by either ingot metallurgy or powder metallurgy. From the viewpoints of material properties and process versatility, powder metallurgy has been widely applied in industries. Generally, stainless steel powders are prepared by atomization processes and powder characteristics, compaction ability, and sinterability are quite different according to the powder preparation process. In the present study, a nanoparticle dispersed micro-sphere powder is synthesized by pulse wire explosion of 316L stainless steel wire in order to facilitate compaction ability and sintering ability. Nanoparticles which are deposited on the surface of micro-powder are advantageous for a rigid die compaction while spherical micro-powder is not to be compacted. Additionally, double step sintering behavior is observed for the powder in the dilatometry of cylindrical compact body. Earlier shrinkage peak comes from the sintering of nanoparticle and later one results from the micro-powder sintering. Microstructure as well as phase composition of the sintered body is investigated.

Preparation and properties of porous silicon nitride ceramics with uniform spherical pores by improved pore-forming agent method

Microsphere powder containing monodisperse polymethylmethacrylate (PMMA) microspheres and Si3N4 particles was prepared by spray-dried method. The homogeneous green body was obtained by using the microsphere powder and Cold Isostatic Pressing (CIP) method. The porous Si3N4 ceramics with uniformly-distributed micron-sized spherical pores were fabricated after sintering under N2 atmosphere. The properties of the samples with differential additions and various sizes of the PMMA microspheres as pore-forming agent respectively were compared. The results showed that the optimal properties of the materials were achieved when the PMMA microspheres with a diameter of 5μm were used as the pore-forming agent. The average bending strength of the samples was 122MPa with a dielectric constant of 3.46, when the porosity was about 51%. The fabrication method is promising for the industrial applications of the porous Si3N4 ceramics with excellent properties.

Criterion conditions for the formation of hollow microspheres from plasma-treated agglomerated particles

A theoretical analysis of the processes proceeding during treatment of agglomerated particles in plasma flows is performed within the context of obtaining hollow microspherical powders from such particles. For the first time, approximate theoretical solutions were used to formulate the criteria to the plasma flow, and also the criteria to the particle material characteristics, whose realization is required for forming hollow microspheres with maximum possible diameter and minimum wall thickness of the particle shell. The study can prove useful for workers engaged in the development of processes for obtaining and application of powder materials.

Formulation Development and In vitro Evaluation of Oral Extended release Capsules Containing Biodegradable Microspheres

Oral extended-release delivery of Biopharmaceutics Classification System (BCS) class II and III compounds is desirable in order to decrease dosing frequency and potential adverse effects. Maintaining an extended-release profile of the drug is ideal to minimize fluctuations in plasma concentrations. The main objective of this research was to formulate a polymeric microsphere drug delivery system that will effectively provide extended-release characteristics via an orally administered capsule. Using acetaminophen and ibuprofen as model drugs, this drug delivery system was shown to provide extended-release characteristics of the drug for enhanced efficacy. The biodegradable polymeric matrix was formulated using bovine serum albumin (BSA) with glutaraldehyde as the crosslinker. The drug of interest was then encapsulated into the polymeric matrix and spray-dried into microspheres. Once prepared, the drug-loaded microsphere powder was placed into hard gelatin capsules. The physicochemical properties of the microsphere formulations were characterized. Additionally, differential scanning calorimetry was utilized to examine the thermal stability of the encapsulated drug. Release studies were conducted in vitro to examine the release profile of the drug. Cell uptake studies were carried out to examine the internalization capability of microsphere formulations. Drugloaded microspheres were found to be approximately 2 microns in size and exhibited a uniform size distribution. Zeta potential measurements were shown to be approximately -30 mV, which indicated that the microspheres are stable in dispersions. Release data showed a constant release of the drug from the microsphere and capsule formulations for at least 16 hours. Formulated microspheres were able to be internalized into human intestinal Caco-2 cells. These data provided evidence for the role of the microsphere delivery system in the extended-release delivery of BCS Class II and III drug substances.

Controllable synthesis and characterization of porous Zn/Cu composite hollow microspheres via a template-free route

In this work, porous Zn/Cu composite hollow microspheres have been successfully prepared via a template-free solution phase route. By controlling the reaction temperature, porous Zn/Cu composite hollow microspheres with the different Zn/Cu mass ratios were achieved. The results from X-ray powder diffraction and X-ray photoelectron spectroscopy show that porous Zn/Cu composite hollow microspheres are Zn/Cu composite but not Zn/Cu alloy, and the composition of the oxide layers is mainly Cu2O phase. Scanning electron microscopic studies indicate that the metallic zinc powder microspheres consist of numerous small particles with an average diameter of about 100 nm, while the composite hollow microspheres are assembled by Zn/Cu composite submicrometer particles with an average diameter of about 500–700 nm. On the basis of these experimental results, a rational formation mechanism is proposed here.

Chitosan microspheres as a delivery system for nasal insufflation

The aim of the present study was to develop and characterize chitosan mucoadhesive microspheres for nasal delivery. The microspheres were prepared by emulsification-crosslinking method and evaluated for morphology, particle size, swelling index, in vitro mucoadhesion and delivery properties from Miat(®) nasal insufflator. The results showed that the microspheres were spherical in shape with smooth surfaces. The particle size of microspheres was found to be dependent on the concentration of the chitosan. The mean particle size was significantly increased when high concentration of chitosan was used. Aqueous to oil phase ratio, stirring rate and dioctyl sodium sulfosuccinate (DOSS) concentration also influenced the particle size distribution of the microspheres. It was found that, as stirring rate was increased, the size of the microspheres was decreased. The volume of glutaraldehyde and crosslinking time had very slight effect on particle size distribution. The % equilibrium water uptake of the microspheres was ranged from 124% to 232% and the mucoadhesive strength from 70.64±2.14 to 86.32±3.96%. The results of powder delivery from the device showed that, almost entire amount was delivered after three puffs. The images of the delivery sequences of microsphere powder clouds demonstrated that microspheres were delivered forming an elongated puff. The core of the clouds was homogeneous which can be expected to provide effective distribution pattern.

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Porous AlN ceramic substrates by reaction sintering

A novel approach was undertaken in producing porous AlN microelectronics tapes with high thermal conductivity and low dielectric constant. This method essentially utilised polymer micro-spherical powders that were used as a sacrificial mould to introduce controlled porosity into the green tapes during pyrolysis. The Al2O3-rich porous green tapes were then reaction sintered at 1680°C for 12h to achieve porous AlN tapes. This work builds upon the previously developed novel reaction sintering process that densified and converted Al2O3-rich tapes (Al2O3–20wt.% AlN–5wt.% Y2O3) to AlN tapes at a relatively low sintering temperature of 1680°C. The sintering behaviour of the porous tapes was investigated, and the effects of the microspheres particle size and volume addition were studied. The microspheres successfully contributed to the significant reduction of tape density by porosity, and this contributed to lowering its dielectric constant. Dielectric constant of the AlN tapes were reduced to about 6.8–7.7 whilst thermal conductivity values were reasonable at about 46–60W/mK. Coefficient of thermal expansion (CTE) values showed a linear trend according to phase composition, with the porous AlN tapes exhibiting CTE values of (4.4–4.8)×10−6°C−1, showing good CTE compatibility with silicon, at 4.0×10−6°C−1. The added porosity did not significantly affect the CTE values.

Porous reaction-sintered AlN tapes for high-performance microelectronics application

A novel approach was undertaken in producing porous AlN microelectronics tapes with high thermal conductivity and low dielectric constant. This method involved polymer microspherical powders used as a sacrificial mold to introduce controlled porosity into the green tapes during pyrolysis. The Al2O3-rich porous green tapes were then reaction sintered at 1680 °C for 12 h to create porous AlN tapes. This work builds upon a previously developed novel reaction sintering process that densified and converted Al2O3-rich tapes (Al2O3–20 wt% AlN–5 wt% Y2O3) to AlN tapes at a relatively low sintering temperature of 1680 °C. The sintering behavior of the porous tapes was investigated, and the effects of the microsphere particle size and volume addition were studied. The microspheres successfully contributed to the significant reduction of tape density by porosity, and this contributed to lowering its dielectric constant. Dielectric constants of the AlN tapes were reduced to about 6.8 to 7.7 while thermal conductivity values were reasonable at about 46 to 60 W/mK. Coefficient of thermal expansion (CTE) values showed a linear trend according to phase composition, with the porous AlN tapes exhibiting CTE values of 4.4 × 10−6 to 4.8 × 10−6/°C, showing good CTE compatibility with silicon at 4.0 × 10−6/°C. The added porosity did not significantly affect the CTE values.

The effect of film thickness and sample history on the parameters describing transport in glassy polymers

The effect of a characteristic dimension of a glassy polymeric specimen on the kinetic mechanism controlling unidirectional absorption of organic vapors and liquids in glassy polymers is demonstrated by comparing n-alkane absorption experiments in microspheres, spheres, films, and sheets of polystyrene. Absorption in submicron microspheres is controlled by Fickian diffusion whereas, under otherwise identical boundary conditions, films (ca. 75μm thick) and spheres (ca. 184 μm in diameter) sorb according to Case II absorption kinetics. Thinner films (35 μm thick) sorb by Super Case II kinetics and relatively thick sheets (2000 μm thick) sorb initially by Case II kinetics but, at long times, diffusion through the outer swollen region contributes significantly to the overall resistance to mass transfer and the rate of absorption decreases progressively with time. p]The rather short experimental times, afforded by the exceedingly small mean diameter of the narrowly distributed microsphere powder sample, permitted convenient characterization of the effects of preswelling, sorption-desorption cycling, and annealing on the kinetics and apparent equilibria of sorption. History effects were quite dramatic and were related to glassy state relaxations initiated by the various thermal and swelling histories imposed upon the glassy microspheres. p]Prediction of sorption and permeation behavior in membranes, from kinetic and equilibrium parameters determined experimentally on film and powder samples, requires explicit recognition of these dimensional and history effects. These effects do not appear to be related to any special properties of this polymer-penetrant system.