Solid Microspheres Research Articles

Role and Effect of Meso-Structuring Surfactants on Properties and Formation Mechanism of Microfluidic-Enabled Mesoporous Silica Microspheres.

We have shown in a previous work that the combination of the emulsion solvent evaporation technique and droplet-based microfluidics allows for the synthesis of well-defined monodisperse mesoporous silica microcapsules (hollow microspheres), whose size, shape and composition may be finely and easily controlled. In this study, we focus on the crucial role played by the popular Pluronic® P123 surfactant, used for controlling the mesoporosity of synthesised silica microparticles. We show in particular, that although both types of initial precursor droplets, prepared with and without P123 meso-structuring agent, namely P123+ and P123- droplets, have a similar diameter (≃30 μm) and a similar TEOS silica precursor concentration (0.34 M), the resulting microparticles exhibit two noticeably different sizes and mass densities. Namely, 10 μm and 0.55 g/cm3 for P123+ microparticles, and 5.2 μm and 1.4 g/cm3 for P123- microparticles. To explain such differences, we used optical and scanning electron microscopies, small-angle X-ray diffraction and BET measurements to analyse structural properties of both types of microparticles and show that in the absence of Pluronic molecules, P123- microdroplets divide during their condensation process, on average, into three smaller droplets before condensing into silica solid microspheres with a smaller size and a higher mass density than those obtained in the presence of P123 surfactant molecules. Based on these results and on condensation kinetics analysis, we also propose an original mechanism for the formation of silica microspheres in the presence and in the absence of the meso-structuring and pore-forming P123 molecules.

Osteogenic potential of solid and porous phosphate glass microspheres as pulp capping materials

This study investigated the morphology (Scanning Electron Microscope), chemistry (Elemental Analysis (EDX), Raman Spectroscopy and X-ray diffraction), thermal characteristics, cytocompatibility, and osteogenic potential of solid and porous phosphate-based glass microspheres for potential use as pulp-capping materials. Cytocompatibility was investigated using human dental pulp stem cells (hDPSCs) through both direct and indirect (extracts) contact tests. Cells grown in normal cell culture medium and 10% dimethyl sulfoxide served as positive and negative controls, respectively. Unlike solid glass microspheres (GMs), porous GMs showed higher CaO mol% and crystalline structure. Both types of GMs supported the attachment, spreading, and viability of hDPSCs similar to the positive control. Cells grown in GMs’ extracts showed even higher viability, but less mineralization than those grown in direct contact with GMs. The presence of osteogenic supplements however did not have a significant effect on mineralisation. Accordingly, both solid and porous GMs show useful applicability as pulp-capping materials.

Template-free formation of BiOCl double-shelled hollow microspheres with enhanced carbamazepine removal efficiency

Constructing three-dimensional (3D) hierarchical structure is regarded as an effective strategy to alleviate the inherent drawbacks of the BiOCl bulk structure and realize the optimization of photocatalytic performance. Herein, a unique BiOCl double-shelled hollow microsphere structure with adjustable shell thickness is fabricated through a template-free one-pot solvothermal method for the first time. A plausible formation mechanism is proposed by exploring the morphological changes during the growth process. The as-obtained hollow microspheres photocatalyst exhibits excellent carbamazepine (CBZ) degradation efficiency (97.5%) under simulated solar irradiation, the corresponding apparent rate constant is about 4 times and 3 times than that of conventional BiOCl solid microspheres. The experimental and characterization results show that the existence of nanosheet subunits and porous structures shorten the diffusion length of charge carriers, which is conducive to the separation and transfer of photogenerated. Meanwhile, the construction of double-shelled hollow structure achieves higher light utilization. This work demonstrates the superior performance of catalysts with hierarchical hollow structures for pollutant degradation and provides new ideas to further optimize the photocatalytic performance of BiOCl-based materials.

Sol-gel fabrication of porous ceria microspheres for thermochemical carbon dioxide (CO2) splitting

Porous CeO2 has been of great interest recently, due to its great catalytic efficiency in splitting CO2 into CO and O2. Porous CeO2 microspheres are the key to scaling up such reactions in the fluidized-bed solar thermochemical reactors. In this paper, we report the processing and CO2 splitting performance of porous ceria microspheres. To fabricate the porous ceria microspheres, homogenous cerium-based sol-gel precursors were synthesized from cerium acetate. The acrylamide (AM) was used as both solidification and pore-generation agent. The polymerization of acrylamide facilitated the conversion of liquid droplets to solid gel microspheres. The optimal AM content was around 20 wt%, ensuring both sufficient porosity and the integrity of the ceria microspheres after thermal decomposition. After heat treatment at 1500 °C for 1 h, porous CeO2 microspheres were obtained, with an average diameter of ∼800 μm and surface area of 2.9 m2/g. These microspheres had high porosity and good sphericity. The CO2 splitting performances of these microspheres were characterized using thermogravimetric analysis (TGA). During the thermal cycles between 1000 and 1400 °C, the O2 yield of porous ceria microspheres was 49 μmol/g, and the CO yield was 88 μmol/g. Compared with porous ceria granules of particle size of ∼800 μm, the porous ceria microspheres exhibited higher O2 and CO production yields. After thermochemical cycles, the microspheres were not sintered together, and the surface area was slightly reduced to 2.7 m2/g.

Direct Visualization of Homogeneous Chemical Distribution in Functional Polyradical Microspheres.

It is demonstrated that the postfunctionalization of solid polymeric microspheres can generate fully and throughout functionalized materials, contrary to the expectation that core-shell structures are generated. The full functionalization is illustrated on the example of photochemically generated microspheres, which are subsequently transformed into polyradical systems. Given the all-organic nature of the functionalized microspheres, characterization methods with high analytical sensitivity and spatial resolution are pioneered by directly visualizing the inner chemical distribution of the postfunctionalized microspheres based on characteristic electron energy loss signals in transmission electron microscopy (TEM). Specifically, ultrasonic ultramicrotomy is combined successfully with electron energy loss spectroscopy (EELS) and electron spectroscopicimaging (ESI) during TEM. These findings open a key avenue for analyzing all-organic low-contrast soft-matter material structures, while the specifically investigated system concomitantly holds promise as an all-radical solid-state functional material.

Ultrasonic Steering Wheels: Turning Micromotors by Localized Acoustic Microstreaming.

The ability to steer micromotors in specific directions and at precise speeds is highly desired for their use in complex environments. However, a generic steering strategy that can be applied to micromotors of all types and surface coatings is yet to be developed. Here, we report that ultrasound of ∼100 kHz can spin a spherical micromotor so that it turns left or right when moving forward, or that it moves in full circles. The direction and angular speeds of their spinning and the radii of circular trajectories are precisely tunable by varying ultrasound voltages and frequencies, as well as particle properties such as its radius, materials, and coating thickness. Such spinning is hypothesized to originate from the circular microstreaming flows localized around a solid microsphere vibrating in ultrasound. In addition to causing a micromotor to spin, such streaming flows also helped release cargos from a micromotor during a capture-transport-release mission. Localized microstreaming does not depend on or interference with a specific propulsion mechanism and can steer a wide variety of micromotors. This work suggests that ultrasound can be used to steer microrobots in complex, biologically relevant environments as well as to steer microorganisms and cells.

Impact of particle size of multivesicular liposomes on the embolic and therapeutic effects in rabbit VX2 liver tumor

Transcatheter arterial chemoembolization (TACE) is usually considered more efficacious in the local treatment of parenchyma-sparing hepatocellular carcinoma (HCC). At present, embolic agents commonly used in TACE, include DC pellets, Hepasphere, Lipiodol, etc. Except that iodine oil is a viscous fluid embolic agent, other solid microsphere particles used clinically range from 70 to 700 µm, among which 100 to 300 µm is the most commonly used. With the technology development of micro-invasive interventional therapy, the specific distal embolization through TACE to occlude tumor arterial blood supply in patients with HCC is also required more accurately. Effective terminal embolization is considered to be a preferred option for TACE therapy due to significantly improving the survival rate of patients and preserving liver function. In this article, we prepared the multifunctional multivesicular liposomes (IVO-DOX-MVLs) (<100 µm) that can simultaneously encapsulate ioversol and doxorubicin based on the high-phase transition temperature (T m) lipid ingredients, and evaluated its local artery embolization and therapeutic effect in rabbit VX-2 tumor model. The influence of particle size on occlusion and therapeutic effect of MVLs on rabbit VX-2 liver tumor models were well evaluated, including the tumor volume change, tumor growth rate, and necrosis rate, which were evaluated by magnetic resonance (MR). MVL samples with average particle size distribution of 50–60 µm exhibited fewer off-target embolization. Through TACE, IVO-DOX-MVLs were directly transported to the tumor tissues, playing roles of embolization performance, CT imaging effect, and local tumor killing effect. The feasibility of MVLs as a multifunctional embolic agent in its clinical application can be further improved by optimization of lipid composition and preparation process.

Bio-characteristics and Efficacy Analysis of Biodegradable Poly Dioxanone Dermal Filler in a Mouse Model and Humans.

This research investigated the biophysical properties, safety, and efficacy of polydioxanone (PDO) filler compared to poly-L-lactic acid (PLLA), polycaprolactone (PCL), and hyaluronic acid (HA) fillers. In both mouse and human skin models, a novel collagen stimulation was compared with hyaluronic acid filler. An electron microscope was used to capture images of the solid particle microsphere shape. Moreover, animal models named SKH1-Hrhr were used to assess the 12-week persistence of PDO, PLLA, or PCL filler. H&E and Sirus Red staining were used to compare collagen density. Five participants in the clinical trial received three injections in the dermis over an eight-month period. Skin density, wrinkles, and gloss were evaluated using DUB® skin scanner, Antera 3D CS, Mark-Vu, and Skin gloss meter after injection to assess the efficacy of fillers. PDO microspheres had uneven surfaces and were spherical and consistent in size. In comparison to other fillers, the PDO filler demonstrated complete biodegradability in just 12 weeks and better neocollagenesis, and a lower inflammatory response than the HA filler. After three injections, the human body assay showed a significant improvement in skin gloss, wrinkles, and density. In comparison to PCL and PLLA, PDO filler demonstrated a comparable volume increase rate and better biodegradability. Furthermore, although its physical characteristics are similar to those of a solid, PDO has the advantage of being more organically spread. In photoaging mice, PDO fillers are thought to offer equivalent or superior anti-wrinkle and anti-aging effects to PBS, PCL, and PLLA.

Road Marking Glass Microspheres Fabricated from Rice Husk Ash

In this work, it is reported a comparison between solid microspheres produced from glass having conventional industrial sand (IS) and glasses made with rice husk ashes (RHA) as a source of silica. The same composition was used to fabricate both glasses. The focused was the production of glass microspheres for road horizontal marking, which would attend the type classification called Premix. The microspheres were obtained by the horizontal flame method. The results showed that characteristics such as production yield, morphology, granulometry and, mainly, retroreflectivity measurements are not altered when rice husk ash is present in the glass composition, showing that this can be a sustainable alternative material for this important application.

Fabrication of bimetallic inlaid working electrode for highly efficient dye sensitized solar cells

Gold nanoparticles (AuNPs) including Au-Pink, Au-Orange, Au-Purple, Au-Blue were synthesized using chemical reduction method, their optical and morphological properties were characterized and they were used in PV devices. The active layer of dye-sensitized solar cells having titanium dioxide (TiO2) solid microsphere (MS) made up of nanoparticles granules were coated with AuNPs. This Au-TiO2 MS hybrid DSSC boosted light harvesting, charge separation, and improved the charge transportresulting in an improvement of both short circuit current and open circuit voltage. The power conversion was boosted 16% compared to the control photoanode of TiO2 solid microsphere. Further enhancement in the short circuit current was observed during the incorporation of both Au and Ag, bi-metallic nanoparticles in the TiO2 matrix. An overall photo to electron conversion efficiency of 8.73% was obtained due to the plasmonic cooperation effect of TiO2-Ag-Au hybrid structures, which is 65% increase over pure TiO2 DSSCs. The local electrified intensity enhancement around the individual Ag, Au nanoparticles and plasmonic coupling of the Ag-Au combination have been used to explain these results with finite-difference time-domain simulation.

Coordination-derived nickel cobalt sulfide solid microspheres with surface defects for high-performance asymmetric supercapacitors

Bimetallic sulfides are effective cathode materials for asymmetric supercapacitors because of their excellent electrochemical properties. However, both the low utilization ratio of the electrode material and the low energy storage capacity have restricted further development. In this work, Ni and Co were reacted with terephthalic acid (H2BDC) and isonicotinic acid (Ina) under hydrothermal conditions, followed by hydrolysis in 1 M KOH and vulcanization in thiourea to yield nickel cobalt sulfide (CoNi2S4) solid microspheres (NiCoS) with surface defects consisting of bumps and holes. These structural and morphological features compensate for the shortcomings of bimetallic sulfide electrodes, enhance their energy storage capacity, and improve their capacitance performance. The specific capacitance of the asymmetric supercapacitor assembled with NiCoS and a self-made carbon electrode reached 168.0 and 101.6 F/g at specific currents of 1 and 20 A/g, respectively. An increase in the specific current by a factor of 20 corresponded to an increase in capacitance retention rate to 60.5%, improving the rate performance. When the specific power increased to 800 and 16 000 W/kg, the specific energy reached 59.7 and 36.2 Wh/kg, respectively. Following 5,000 charge/discharge cycles, the capacitance retention rate was 96.78%. Such excellent comprehensive electrochemical performance greatly increases the competitiveness of the NiCoS electrode in the field of electrochemical energy storage.

3D Gelatin Microsphere Scaffolds Promote Functional Recovery after Spinal Cord Hemisection in Rats.

Spinal cord injury (SCI) damages signal connections and conductions, with the result that neuronal circuits are disrupted leading to neural dysfunctions. Such injuries represent a serious and relatively common central nervous system condition and current treatments have limited success in the reconstruction of nerve connections in injured areas, especially where sizeable gaps are present. Biomaterial scaffolds have become an effective alternative to nerve transplantation in filling these gaps and provide the foundation for simulating the 3D structure of solid organs. However, there remain some limitations with the application of 3D bioprinting for preparation of biomaterial scaffolds. Here, the approach in constructing and testing mini-tissue building blocks and self-assembly, solid 3D gelatin microsphere (GM) scaffolds with multiple voids as based on the convenient preparation of gelatin microspheres by microfluidic devices is described. These 3D GM scaffolds demonstrate suitable biocompatibility, biodegradation, porosity, low preparation costs, and relative ease of production. Moreover, 3D GM scaffolds can effectively bridge injury gaps, establish nerve connections and signal transductions, mitigate inflammatory microenvironments, and reduce glial scar formation. Accordingly, these 3D GM scaffolds can serve as a novel and effective bridging method to promote nerve regeneration and reconstruction and thus recovery of nerve function after SCI.

Template-free hydrothermal synthesis of hollow alumina microspheres and its excellent catalytic properties for thiolation

In view of the important industrial application value of alumina supports in the field of oil refining and reforming, it is of great significance to develop a simple and economical synthesis method for the hierarchical porous alumina. Herein, the hollow microsphere alumina was hydrothermally synthesized without template. The surface of the hollow microsphere alumina supports has a raised fluffy structure, the microsphere diameter is about 5 ∼ 8 μm, and the thickness of the shell is about 1 μm. The morphology evolution process from solid microspheres to core–shell microspheres with spindle-shaped nanoclusters, and then to hollow fluffy microspheres with protruding surface was observed by investigating the effect of hydrothermal synthesis temperature on the morphology of microspheres. Because of its specific morphology and surface characteristics, the microsphere can better disperse the active component KW to prepare KW/Al2O3 catalyst and used in the thiolation to methyl mercaptan. Compared with our previously used catalysts prepared from commercial alumina, this KW/Al2O3 catalyst was not only able to greatly reduce the amount of active component, but also exhibited higher CH3SH selectivity. On the 10KW/Al catalyst, the CH3SH selectivity reached 66.2 % at 340 °C, which was about 10 % higher than that of the previous commercial alumina catalyst. This work can provide theoretical basis and practical guidance for the reasonable design of new alumina support and high efficiency methyl mercaptan catalyst.

Advancements in Rectal Drug Delivery Systems: Clinical Trials, and Patents Perspective

The rectal route is an effective route for the local and systemic delivery of active pharmaceutical ingredients. The environment of the rectum is relatively constant with low enzymatic activity and is favorable for drugs having poor oral absorption, extensive first-pass metabolism, gastric irritation, stability issues in the gastric environment, localized activity, and for drugs that cannot be administered by other routes. The present review addresses the rectal physiology, rectal diseases, and pharmaceutical factors influencing rectal delivery of drugs and discusses different rectal drug delivery systems including suppositories, suspensions, microspheres, nanoparticles, liposomes, tablets, and hydrogels. Clinical trials on various rectal drug delivery systems are presented in tabular form. Applications of different novel drug delivery carriers viz. nanoparticles, liposomes, solid lipid nanoparticles, microspheres, transferosomes, nano-niosomes, and nanomicelles have been discussed and demonstrated for their potential use in rectal administration. Various opportunities and challenges for rectal delivery including recent advancements and patented formulations for rectal drug delivery have also been included.

Preparation and Microwave Absorbing Properties of Yolk Shell C@C Microspheres

As a typical dielectric loss medium, carbon material has always been the most attractive candidate material for microwave absorption because of its characteristic advantages. However, much less attention has been paid to the reasonable design of micro-structure to improve its performance. According to the transmission behavior and loss mechanism of electromagnetic wave, uniform yolk shell C@C microspheres as a new type of microwave absorbers were creatively prepared by "coating-coating-etching". Compared with solid carbon microspheres, the unique micro-structure endows better BET surface and pore volume to the yolk shell C@C microspheres. The microwave absorption performance was tested in the frequency range of 2GHz to 18GHz. As expected, the yolk shell C@C microspheres exhibit excellent reflection loss characteristics, with strong reflection loss (-41.84dB at 9.2GHz) and wide effective absorption bandwidth(7.9~10.2GHz). This good performance is so for indeed better than most pure carbon absorbers reported. The electromagnetic parameters show that the yolk shell structure is conducive to the matching of characteristic impedance and can obtain ideal microwave absorption ability.

Design and Evaluation of Solid Lipid Microparticles of Curcumin for the Treatment of Alzheimer’s Disease

A solid lipid Microparticle reaches to the target site at controlled rate and show controlled release for better therapeutic result. This drug delivery system are prepare to obtained prolonged sustained or controlled drug delivery, to improves bioavailability, to enhance stability and to reduce toxic effects follows with target drug at specific site. The solid lipid micro particles of curcumin were prepared in a view to achieve high permeability of curcumin in brain through blood-brain-barrier. The solid lipid microspheres are prepared by hot melts microencapsulation technique was used to formulate solid lipid microspheres. Twelve formulations were prepared by varying concentration of surfactants (span 20, span 60, span 80 and Tween 80). The developed formulation were subjected to various parameter such as the particle size, % entrapment efficiency, production yield, % 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 were subjected to different evaluation parameter such as melting point, thin layer chromatography, solubility, FTIR, compatibility study and In-vitro drug release. The developed formulation shows spherical and smooth surface. The % drug release of F3 formulation was found to be 86.23% after 12 hr.

Biomimicking nanofibrous gelatin microspheres recreating the stem cell niche for their ex-vivo expansion and in-vivo like differentiation for injectable stem cell transplantation.

Stem cells based novel treatment modality for degenerative and immune dysfunction diseases created a huge demand of suitable carriers to support ex-vivo production of quality stem cells, and effective in-vivo transplantation of stem cells and their fate. In spite of promising candidature of nanofibrous microspheres (NFM) to recreate native stem cell niches to be used for possible scaling-up for ex-vivo stem cells expansion, it remains fairly unexplored. A systematic study on the stem cell-NFM interaction comparative with commercial microspheres (CM) has been performed for the first time. Gelatin NFM with variable physicochemical properties such as size, surface properties, surface chemistry, and variable degradability were prepared using microemulsion coupled with thermally induced phase separation (TIPS) method. Effect of physicochemical properties of NFM and their cellular interaction such as binding, morphology, metabolic activity and proliferation studies were performed using human bone marrow-derived mesenchymal stem cells (hBMSCs), human dental follicle stem cells (hDFSCs) and human gingival fibroblast (HGF) cells and compared with the commercial and solid microspheres. Gelatin NFM supports excellent cell binding, proliferation, metabolic activities and chemical cues specific differentiation. All out-turns indicate that NFM stand to be an outstanding candidate for ex-vivo cells' expansion and injectable carriers for stem cell transplantation.

Treatment of Tuberculosis in Nano Era: Recent Avenues

Abstract: Tuberculosis (TB) is a life-threatening infectious disease caused by the bacteria Mycobacterium tuberculosis (MTB), which mostly affects the lungs. According to the World Health Organization (WHO) report 2020, there were over 10 million cases of tuberculosis worldwide, with around 1.4 million people dying, wherein India accounts for over 26% of the global burden. Prolonged treatment, high pill burden, low compliance, development of multiple drug resistance and subsequent intolerable toxicity lead to the emergence of new nanotechnology-based drug delivery approaches involving micro-metric and nano-metric carriers. Nanotechnology is superior to conventional therapies as it offers site specific drug delivery of antimicrobial drugs that increases therapeutic efficacy and reduces systemic toxicity associated with higher doses and also prevents the drug from early degradation, increased solubility and blood retention time. This review focuses on the different nanotechnological carriers via pulmonary route, including liposomes, niosomes, solid lipid nanocarriers, dendrimers, nanoparticles, microspheres and microparticles for tackling the problems related to the treatment of TB. The current review gives a summary of the possible utilization of nanotechnology-based carrier systems to overcome the disadvantages of TB therapy. It also provides a summary of the importance and advancements of directing nanocarriers at bacterial reservoir. Eventually, the article presents an overview of the success in clinical application of such systems.

Self-transformation of solid CaCO3 microspheres into core-shell and hollow hierarchical structures revealed by coherent X-ray diffraction imaging.

The self-transformation of solid microspheres into complex core-shell and hollow architectures cannot be explained by classical Ostwald ripening alone. Here, coherent X-ray diffraction imaging and 3D X-ray fluorescence were used to visualize in 3D the formation of hollow microparticles of calcium carbonate in the presence of polystyrene sulfonate (PSS). During the dissolution of the core made from 10-25 nm crystals, the shell developed a global spheroidal shape composed of an innermost layer of 30 nm particles containing high PSS content on which oriented vaterite crystals grew with their c axis mainly oriented along the meridians. The stabilizing role of PSS and the minimization of the intercrystal dipolar energy can explain in combination with Ostwald ripening the formation of these sophisticated structures as encountered in many systems such as ZnO, TiO2, Fe2O3, Co3O4, MnO2, Cu2O, ZnS, CaCO3 and Ca8H2(PO4)6·5H2O.

Formulation and evaluation of polymeric microspheres of a poorly soluble drug celecoxib

The aim of this present work was to formulate microspheres of BCS Class II drug Celecoxib. The drug was identified by melting point study and FT-IR spectroscopy. Therapeutic success of a drug is greatly depended on its bioavailability. Majority of the recently discovered drugs shows poor solubility (BCS Class II) which decreases the bioavailability upon oral administration. Microspheres are a novel technique to circumvent this obstacle, which can increase bioavailability of drugs significantly. Polymeric microspheres with Polyvinylpyrrolidone and Eudragit L-100, prepared by Emulsion Solvent Diffusion and Evaporation technique, showed a range of drug release profile at intestinal pH 6.8. Different batches of microspheres were prepared by varying the drug-polymer ratio. Microparticulate systems like microspheres improve absorption which increases the bioavailability, ultimately leading to more efficient drug therapy. The microsphere system also provides protection to the gastric mucosa from GIT-irritant drugs thus decreasing toxic effects and sustained releases allows lower dosage frequency. Prepared microspheres were evaluated on various parameters like entrapment efficiency, %yield, particle size, scanning electron microscope analysis, and in-vitro drug release profile. Solid spherical microspheres were produced which showed good entrapment efficiency (43%-91%) and released 70-90% of the drug content in 10hrs.