Solid Microspheres Research Articles

Tunable organic particles: An efficient approach from solvent-dependent Schiff base macrocycles

The synthesis of cyclopolymers upon controlling the degree of macrocyclic polymerization, followed by the discovery of new properties has attracted increasing attention in supramolecular chemistry. Herein, a Schiff-base condensation method performed at room temperature was used to control the formation of [1 + 1] and [2 + 2] macrocycles. In pure MeOH, the isomer [1 + 1] macrocycles were synthesized and organic particles such as dendritic, rods, and solid microspheres were directly precipitated from the reaction solution. The [1 + 1] macrocycles can be efficiently converted into their corresponding [2 + 2] macrocycles accompanied by the tunable morphology of the organic particles when n-hexane was added to the MeOH solution. Further studies showed that these organic particles have potential application toward the selective removal of Cd2+ ions with different adsorption ability in MeOH solution.

Urchin-like Hydroxyapatite/Graphene Hollow Microspheres as pH-Responsive Bone Drug Carriers.

Hydroxyapatite (HA) is the main inorganic component of human bones and teeth. It has good biocompatibility and bioactivity, which promotes its good application prospects in the field of bone drug carriers. In this study, tetraethylenepentamine-graphene (rGO-TEPA)/CaCO3:HA composite microspheres were prepared via microwave hydrothermal synthesis using rGO-TEPA/CaCO3 solid microspheres as intermediates. Furthermore, the incompletely transformed CaCO3 was removed by soaking in a citric acid buffer to obtain rGO-TEPA/HA hollow composite microspheres. The two types of as-prepared composite microspheres exhibited sea urchin-like structures, large BET surface areas, and good dispersibility. Mouse preosteoblast cells (MC3T3-E1) were used for in vitro cytotoxicity experiments. The in vitro cell viability test showed that the two composite drug carriers exhibited noncytotoxicity. Moreover, the doxorubicin (DOX) loading and releasing investigations revealed that the two types of prepared carriers had mild storage-release behaviors and good pH responsiveness. Hence, these rGO-TEPA/HA hollow microspheres have promising applications as bone drug carriers.

Multishelled NiO/NiCo2O4 hollow microspheres derived from bimetal-organic frameworks as high-performance sensing material for acetone detection

Recently, tremendous research interest was stimulated to obtain advanced function materials with hierarchical structure and tailored chemical composition from metal-organic frameworks (MOFs) based precursors. Herein, Bimetal-organic frameworks of Ni-Co-BTC solid microspheres synthesized through hydrothermal method were acted as template to induce multishelled NiO/NiCo2O4 hollow microspheres by annealing treatment. When evaluated as gas sensing material, the optimal hybrid of NiO/NiCo2O4 (the molar ration of NiCo=1.5) multishelled hollow microspheres endowed a high sensitivity (17.86) to 100 ppm acetone with rapid response/recovery time (11/13 s) under low working temperature (160 °C) and the low detection limit reached 25 ppb. The enhanced mechanism was originated from the following aspects: the multishelled hollow architecture provided efficient diffusion path for gas molecules and sufficient active site for gas sensing reaction; the nanoscale p-p heterojunction created at NiO and NiCo2O4 nanoparticles interface amplified the resistance variation by tuning the potential barrier; the potent combination of the “chemical catalytic” effect of NiO and the “electrical catalytic” effect of NiCo2O4 improved the selective acetone detection.

Fabrication of solid CH-CD multilayer microspheres for inertial confinement fusion

Deuterated polymer microspheres can be used as a neutron source in conjunction with lasers because thermonuclear fusion neutrons can be produced efficiently by collisions of the resulting energetic deuterium ions. A new type of solid deuterated polymer microsphere with a carbon hydrogen–carbon deuterium (CH-CD) multilayer has been designed for preparing the target for inertial confinement fusion (ICF) experiments. To fabricate these solid CH-CD multilayer microspheres, CH beads are first fabricated by a microfluidic technique, and the CD coating layer is prepared by a plasma polymerization method. Both polystyrene (PS) and poly(α-methylstyrene) (PAMS) are used as the material sources for the CH beads. The effects of the PS and PAMS materials on the quality of the solid CH beads and the resulting CH-CD multilayer polymer microspheres are investigated. The solid PS beads have better sphericity and a smoother surface, but large vacuoles are observed in solid PS-CD multilayer microspheres owing to the presence of residual fluorobenzene in the beads and a glass transition temperature of the solid PS beads that is lower than the temperature of plasma polymerization. Therefore, solid PAMS beads are more suitable as a mandrel for fabricating solid CH-CD multilayer polymer microspheres. Solid CH-CD multilayer microspheres with specified size have been successfully prepared by controlling the droplet size and the CD deposition rate and deposition time. Compared with the design value, the diameter deviation of the inner CH beads and the thickness deviation of the CD layer can be controlled within 20 µm and 2 µm, respectively. Thus, an approach has been developed to fabricate solid CH-CD multilayer microspheres that meet the physical design requirements for ICF.

Formulation Design and Evaluation of Solid Lipid Micro-particles of Curcumin for the Treatment of Alzheimer’s disease

Solid lipid microparticles reach the site of its action in a controlled rate and do show controlled release for a better therapeutic result. A good drug carrying and release system involve a controlled drug delivery that improves bioavailability, to enrich stability and to minimise the toxic effects followed with a targeted drug at the site of its action. The solid lipid microparticles of curcumin were prepared in a view to achieving high permeability of curcumin in the brain through blood-brain-barrier. The lipid microsphere solids were prepared by hot melts microencapsulation technique to formulate solid lipid microspheres. Twelve lipid formulations were prepared with varying concentration of surfactants (span 40, span 70, span 90 and Tween 100). The developed formulation was subjected to various parameters such as the particle size, % entrapment efficiencies, yield productions, % cumulative release, percentage yield and drug loading, based upon highest entrapment efficiency, drug release and % cumulative release, the F3 formulation was considered as the best formulation. The prepared microsphere was subjected to different evaluation parameters such as thin-layer chromatography, melting point, FTIR, solubility, compatibility study and In-vitro drug release. The developed formulation shows spherical and smooth surface. The percentage release of drug F3 formulation has been found highest of about 86.23% after 12 hr.

Functional monodisperse microspheres fabricated by solvothermal precipitation co-polymerization

Simultaneous achievement in high solid content and high microsphere yield is deemed a challenge in the fabrication of monodisperse microspheres by precipitation polymerization. We herein demonstrate that micro-sized monodisperse poly(methacrylic monomer-divinylbenzene) microspheres containing epoxy, lauyl, carboxyl and hydroxyl functions can be fabricated by solvothermal precipitation co-polymerization at 20% (mass) monomer loading with over 94% microsphere yield. The morphology and porosity of the obtained particles can be readily tuned by cosolvent-acetonitrile binary solvents. Addition of a small amount of cosolvent that has similar solubility parameter to that of the functional monomer can significantly improve the monodispersity of the obtained microspheres. When tetrahydrofuran was used as the co-solvent, the surface area of the highly porous microspheres achieved higher than 400 m 2 ·g −1 . Solvothermal precipitation co-polymerization can be expected in scale-up fabrication of various monodisperse functional microspheres free of any surfactant and additive.

Effect of varying the Mg with Ca content in highly porous phosphate-based glass microspheres

This paper reports on the role of phosphate-based glass (PBG) microspheres and their physicochemical properties including in vitro biological response to human mesenchymal stem cells (hMSCs). Solid and porous microspheres were prepared via a flame spheroidisation process. The Mg content in the PBG formulations explored was reduced from 24 to 2 mol% with a subsequent increase in Ca content. A small quantity of TiO2 (1 mol%) was added to the lower Mg-content glass (2 mol%) to avoid crystallisation. Morphological and physical characterisation of porous microspheres revealed interconnected porosity (up to 76 ± 5 %), average external pore sizes of 55 ± 5 μm with surface areas ranging from 0.38 to 0.43 m2 g−1. Degradation and ion release studies conducted compared the solid (non-porous) and porous microspheres and revealed 1.5 to 2.5 times higher degradation rate for porous microspheres. Also, in vitro bioactivity studies using simulated body fluid (SBF) revealed Ca/P ratios for porous microspheres of all three glass formulations were between 0.75 and 0.92 which were within the range suggested for precipitated amorphous calcium phosphate. Direct cell seeding and indirect cell culture studies (via incubation with microsphere degradation products) revealed hMSCs were able to grow and undergo osteogenic differentiation in vitro, confirming cytocompatibility of the formulations tested. However, the higher Mg content (24 mol%) porous microsphere showed the most potent osteogenic response and is therefore considered as a promising candidate for bone repair applications.

Synthesis and Characterization of Cu2FeSnS4-Cu2MnSnS4 Solid Solution Microspheres.

In this study, we used a hydrothermal method to synthesize microspheres of Cu2(Mn1−xFex)SnS4 solid solution (X = 1, 0.8, 0.6, 0.4, 0.2, 0). The process was optimized to improve the crystallinity, morphology, and purity of the obtained materials. All samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The following conditions were optimized: A mixture of water and ethylene glycol at the ratio of 1:7 as the reaction medium, polyvinylpyrrolidone (PVP) as the surface ligand, and reaction temperature of 195 °C for 7 days. The product of synthesis precipitated in the form of aggregates of nanocrystals, which form homogeneous, often concentric microspheres with a diameter of 1–1.5 μm. The chemical composition of the product can be well controlled by the chemical composition of the reactants. The compound Cu2(Mn1−xFex)SnS4 forms a continuous series of solid solutions.

Low-Cost magnetic adsorbent for efficient Cu(II) removal from water

Selective adsorption using magnetic adsorbent is supposed as one of the most effective methods for heavy metal removal from water for the advantage of efficient solid-liquid separation. However, the application of this technique is hindered by the high cost, unfavorable environmental effects of the chemical synthesis of magnetic adsorbents. In this study, the industrial waste coal-fly-ash magnetic sphere (CMS) were carefully processed to prepare cheap and green magnetic core material. Then, a composite bioadsorbent using CMS as core and chitosan (CS) as the shell (CMS@CS for short) was fabricated via an extrusion-dripping method. Structural investigations indicate that the obtained CMS@CS samples are hollow microsphere with a solid wall or porous solid microsphere depending on the preparation conditions. CMS particles are evenly distributed in both microspheres. The porous sample has an 81.49 m2 g−1 special surface area, 96 times larger than the hollow. The highest Cu(II) adsorption of the porous sample is measured as 22.41 mg g−1, 3.6 times larger than that of the hollow. The Cu(II) adsorption of the CMS@CS samples is closely related to the internal structure, surface chemical modification, and solution pH. The adsorption mechanism could be explained by a two-step procedure model. The CMS@CS adsorbents have an average magnetism of 10.07 emu g−1, thus could be magnetically separated efficiently. The density of CMS@CS is tested as 1.45–1.65 g cm−3. A similar density with water would improve its suspend ability in the water. The used CMS@CS adsorbent could be recycled several times after appropriate treatment.

Dry sliding wear characterization of SGM/boron carbide hybrid polymer matrix composite

The purpose of this investigation is wear characterization of solid glass microspheres (SGM) and boron carbide (BC)-reinforced epoxy composites, under dry sliding conditions using a pin-on-disk wear test machine. Influence of parameters like sliding distance, sliding velocity, applied load and addition of fillers, on the wear rate were examined. Taguchi technique was used for the plan of experiments to conduct wear tests. To evaluate the effect of the individual parameters on the rate of wear performance of composites, analysis of variance (ANOVA) and an orthogonal array were employed. Linear regression analysis was employed for all the composites to establish an empirical relation between the various process parameters and wear. The results indicate reduction in wear of polymer on addition of particulates with the lowest wear rates observed in composites with addition of boron carbide as filler. Different fracture mechanisms were revealed by Scanning electron microscope (SEM) images of worn-out composite surfaces.

Reflectivity of solid and hollow microsphere composites and the effects of uniform and varying diameters

While solid and hollow microsphere composites have received significant attention as solar reflectors or selective emitters, the driving mechanisms for their optical properties remain relatively unclear. Here, we study the solar reflectivity in the 0.4–2.4 μm wavelength range of solid and hollow microspheres with the diameter varying from 0.125 μm to 8 μm. SiO2 and TiO2 are considered as low- and high-refractive-index microsphere materials, respectively, and polydimethylsiloxane is considered as a polymer matrix. Based on the Mie theory and finite-difference time-domain simulations, our analysis shows that hollow microspheres with a thinner shell are more effective in scattering the light, compared to solid microspheres, and lead to a higher solar reflectivity. The high scattering efficiency, owing to the refractive-index contrast and large interface density, in hollow microspheres allows low-refractive-index materials to have a high solar reflectivity. When the diameter is uniform, 0.75 μm SiO2 hollow microspheres provide the largest solar reflectivity of 0.81. When the diameter is varying, the randomly distributed 0.5–1 μm SiO2 hollow microspheres provide the largest solar reflectivity of 0.84. The effect of varying diameter is characterized by strong backscattering in the electric field. These findings will guide optimal designs of microsphere composites and hierarchical materials for optical and thermal management systems.

Anti-inflammatory, Anxiolytic and Antioxidant Property of Lactuca sativa L and Formulation of Microspheres Loaded Sustained Release Anti-inflammatory Gel

Anti-inflammatory and anxiolytic properties of Lactuca sativa L extract was evaluated by formalin induced mice paw edema test, and elevated plus maze animal model respectively. Solid microspheres containing dispersed extract were obtained by water-in-oil-in-water multiple emulsion system followed by solvent evaporation method. Optimization was carried out using MINITAB 16 and optimized microspheres were loaded into a gel base. Anti-oxidant activity of optimized microspheres loaded gel was evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. The gel was also evaluated for its physical properties, drug release kinetics and anti-inflammatory activity using formalin induced mice-paw edema test where the anti-inflammatory potential was compared to marketed diclofenac gel (1.16% w/w). All doses of extract as well as microsphere loaded sustained release anti-inflammatory gel showed a dose and time dependent inhibition of edema (P<0.05), the extract also showed a dose dependent inhibition of level of anxiety (P<0.001). Potential anti-oxidant activity was seen with different concentration of crude extract and microsphere loaded gel. The anti-oxidant potential was compared using IC50 value which was 5.62 µg/mL, 6.34 µg/ml, 8.25 µg/mL for ascorbic acid, methanolic extract of L. sativa and microspheres loaded gel respectively.

Fabrication of Microspheres from High-Viscosity Bioink Using a Novel Microfluidic-Based 3D Bioprinting Nozzle.

Three-dimensional (3D) bioprinting is a novel technology utilizing biocompatible materials, cells, drugs, etc. as basic microcomponents to form 3D artificial structures and is believed as a promising method for regenerative medicine. Droplet-based bioprinting can precisely generate microspheres and manipulate them into organized structures with high fidelity. Biocompatible hydrogels are usually used as bioinks in 3D bioprinting, however, the viscosity of the bioink could be increased due to the additives such as cells, drugs, nutrient factors and other functional polymers in some particular applications, making it difficult to form monodispersed microspheres from high-viscosity bioink at the orifice of the nozzle. In this work, we reported a novel microfluidic-based printing nozzle to prepare monodispersed microspheres from high-viscosity bioink using the phase-inversion method. Different flowing conditions can be achieved by changing the flow rates of the fluids to form monodispersed solid and hollow microspheres using the same nozzle. The diameter of the microspheres can be tuned by changing the flow rate ratio and the size distribution of the microspheres is narrow. The prepared calcium alginate microspheres could also act as micro-carriers in drug delivery.

Three-dimensional ordered macroporous magnetic photonic crystal microspheres for enrichment and detection of mycotoxins (I):Droplet-basedmicrofluidicself-assemblysynthesis.

Ordered porous materials are attracting enormous attention due to their uniform pore structures, particularly the magnetic photonic crystal microspheres (PCMs) which not only possess unique photonic crystal structure but also can achieve separation easily based on magnet. Here, a two-phase microfluidic self-assembly synthetic system was established simply and employed for the preparation of three dimensional PCMs (3DPCMs) by using the emulsion droplet approach. One phase (dispersed phase) was an aqueous emulsion containing Fe3O4, silica (SiO2) and polystyrene (PS) nanoparticles; another phase (continuous phase) was pure silicone oil. The droplets were formed by introducing the dispersed phase into the continuous phase through a tee valve. By heating the droplets, the water would evaporate and the nanoparticles would finally assemble into solid microspheres, which could be changed into macroporous 3DPCMs after removal of the PS nanoparticles by calcination. The contents and particle sizes of Fe3O4, SiO2 and PS nanoparticles in the dispersed phase were investigated in detail and optimized to prepare macroporous magnetic 3DPCMs with high quality. The morphologies, surface crystal structure, magnetic property, particle size distribution, specific surface area and pore size of the macroporous magnetic 3DPCMs were characterized. The expected 3DPCM displayed regular and uniform photonic crystal structure, narrow particle size distribution and strong magnetic property. The macroporous magnetic 3DPCMs grafted with vomitoxin (DON)-antibodies could be applied for selective enrichment of DON in real samples.

Screen printed multifunctional TiO2 photoanode with plasmonic Ag nanoparticles for performance enhancement of dye sensitized solar cell

Multifunctional TiO2 powder consisting of solid microspheres/nanoparticles (NPs) was obtained in single step hydrothermal method. The insights of mesoporous solid TiO2 microspheres are observed as interconnected particles granules in the field emission scanning electron microscope (FESEM) investigation. Secondly, Ag nanoparticles (AgNPs) of spherical shaped with narrow size distribution was synthesised by reduction process and its extinction maximum at 413 nm was observed from UV–Vis analysis. Screen printed TiO2 photoanode containing plasmonic AgNPs was utilised to construct the dye sensitized solar cell (DSSC). The efficiency and optical properties of the bare and plasmonic devices were compared. Noticeable improvement in device efficiency is attributed to plasmonic properties of the incorporated AgNPs.

A hybrid system of hydrogel/frog egg‐like microspheres accelerates wound healing via sustained delivery ofRCSPs

AbstractIn this article, a hybrid system of hydrogel/frog egg‐like microspheres (H‐FMS) formed by the combination of coaxial electrostatic spraying and freeze‐drying was introduced for enhancing wound healing efficiency through the sustained release ofRana chensinensisskin peptides (RCSPs). The porous PVA/gelatin hydrogel were obtained and frog egg‐like microspheres (FMS) of sodium alginate (SA), shaping uniform and smooth, were embedded into hydrogel. Based on PVA/gelatin hydrogel, the FMS addition increased the water absorption of hydrogel to 1,105%. RCSPs were more effectively encapsulated into FMS than solid microspheres (MS). Not only does the H‐FMS act as good “depots” for sustained release of RCSPs over 9 days, without exhibiting obvious burst release, but also show good biocompatibility in vitro. In vivo studies on wound healing as well as the histology of fibroblasts, re‐epithelialization, inflammation, and hair follicles indicated that the structure of H‐FMS released RCSPs continuously and promoted wound healing in rats significantly.

Single crystalline hierarchical SnO2 microsphere and fluoride-mediated hollow structures for photocatalytic activity

The present research study deals with the preparation of tin oxide (SnO2) nanostructures hierarchical hollow microspheres and composed of oriented aligned cone-like SnO2 nanoparticles are prepared by a hydrothermal route using either NH4F as morphology controlling agents. The samples were morphology characterized by FE-SEM with diameter of about 2 μm to 50 nm and XRD showed a homogeneous distribution of quite small grains over scanned area. The FT-IR result shows the stretching vibration of the hierarchical SnO2 solid or hollow microspheres nanoparticles due to its chemical interaction. The optical properties were studied using UV absorption and its opticalband gap value is 3.9 eV. The electrochemical performance of SnO2 tested to determine the oxidation/reduction processes by cyclic and linear sweep voltammetry.

Thermal, acoustic, and dielectric behavior of epoxy-based hybrid composites using short hair fiber

This study aims at investigating the thermal, acoustic, and dielectric behavior of a class of epoxy-based hybrid composite incorporated with, short human hair fibers (SHF), and solid glass microspheres (SGM). Epoxy composites filled with 10 wt% of SGM are prepared by solution casting method with different loadings (0, 5, 10, 15, 20 wt%) of SHF. Thermal properties of these composites such as thermal conductivity (K), coefficient of thermal expansion (CTE), and glass transition temperature (Tg) are evaluated by conducting tests as per appropriate ASTM standards. An impedance tube tester and a HIOKI-3532-50 Hi Tester Elsier Analyzer are used for measuring the sound absorption coefficient and dielectric constant of the composite samples, respectively. A theoretical model has been developed to predict the effective thermal conductivity of the hybrid composite considering minimal thermal contact resistance. Based on this model, a mathematical correlation between the effective thermal conductivity of the composite and the filler content is proposed. The results obtained from this correlation are found to be in good agreement with the experimental data. It is observed that with the increase in fiber content the thermal and acoustic insulation behavior of the hybrid composite has been significantly improved. The dielectric characteristics of the composites are also found to be substantially affected by the fiber content and operating frequency.

Preparation and characterization of a novel ethanol gas sensor based on FeYO3 microspheres by using orange peels as bio-templates

The perovskite Iron Yttrium Oxide (FeYO3) microspheres on the basis of bio-templates with orange peels have been successfully obtained by a facile hydrothermal ‘green synthesis’ along with multifarious characterization techniques. The XRD demonstrated that the synthesized sample was single phase FeYO3 with a hexagonal perovskite structure. Moreover, the solid microspheres with relatively rough surfaces were displayed by SEM and TEM. Benefiting from this fact, the sensor based on p-type semiconductor FeYO3 microspheres showed good gas sensing characteristics towards ethanol at the optimum operating temperature of 330 °C with a low detection limit (1 ppm), good repeatability and fast response/recover time, etc. Accordingly, this work supplies a good experimental basis for FeYO3 as a novel semiconductor gas sensing material soon.

Taste masking of water-soluble drug by solid lipid microspheres: a child-friendly system established by reversed lipid-based nanoparticle technique.

A child-friendly taste-masking strategy using solid lipid microsphere (SLM) has been proposed to obscure the undesirable taste of some water-soluble drugs. In this study, the reversed lipid-based nanoparticle (RLBN) technique was used to encapsulate a water-soluble drug to facilitate the preparation of SLM. The model drug used was atomoxetine hydrochloride (ATX), and a three-step method was used to prepare ATX-RLBN. Taste-masking microsphere (ATX-RLBN-SLM) was prepared by the spray chilling method. The drug release mechanism was studied by high-performance liquid chromatography and scanning electron microscopy. Moreover, in vitro taste evaluation method was established and ATX bioavailability was investigated employing pharmacokinetic studies. The obtained ATX-RLBN-SLM had smooth spherical particles with a size of about 80μm. The drug encapsulation and loading efficiencies were 98.28%±0.59% and 0.89%±0.04%, respectively. In vitro drug release studies showed that nearly 96% drug was retained in the microspheres within 10min at pH 6.8 and a complete release was triggered by lipase, accompanied by variation in the morphology. Taste assessment revealed that ATX-RLBN-SLM could efficiently mask the bitter taste and improved the bioavailability of ATX. Atomoxetine hydrochloride-reversed lipid-based nanoparticle-solid lipid microsphere exhibited excellent taste-masking effect with negligible leakage in the oral cavity environment and thorough collapse upon lipase stimulation, simultaneously enhancing the bioavailability of ATX. The study paves a new way to efficiently mask the undesirable taste of some water-soluble drugs.