Inorganic Microparticles Research Articles

Determination of the spectral dependence for the absorption coefficient of phosphor inorganic microparticles

Determination of the spectral dependence for the absorption coefficient of phosphor inorganic microparticles

Silk fibroin hydroxyapatite composite thermal stabilisation of carbonic anhydrase

Hybrid organic–inorganic micro-particles have been prepared by a phosphate ultrasound treatment to immobilise carbonic anhydrase. These hierarchical structures show a noteworthy thermal stability in alkanolamine solvent used for CO2 sequestration and allow an easy separation and re-use.

Complex-shaped microbial biominerals for nanotechnology.

Single-celled microorganisms such as diatoms and coccolithophores produce inorganic microparticles with genetically controlled hierarchical nanopatterns. Besides serving as paradigms to inspire new routes for materials synthesis, biominerals themselves, particularly diatom biosilica, are increasingly utilized as templates for the synthesis of novel functional materials. Over the past decade, a large variety of methods have been established that allow not only for the attachment or coating of desired materials onto diatom biosilica but also for complete chemical conversion without altering the characteristic micro- and nanoscale morphology. Examples include the synthesis of materials for photonics (surface-enhanced Raman spectroscopy, SERS, extraordinary optical transmission, EOT), ultraresponsive and sensitive gas sensors, gas storage materials, and highly active catalysts. More recently, emerging insight into the cellular mechanisms of biosilica formation has enabled the in vivo functionalization of diatom biosilica through advanced cultivation techniques and genetic engineering. As a naturally renewable material, biominerals hold the promise of serving as an inexpensive and easily available resource for a future nanotechnology-based industry.

Conjugated polymer shells on colloidal templates by seeded Suzuki–Miyaura dispersion polymerization.

The self-assembly of colloidal conjugated polymers presents a versatile and powerful oute towards new functional optoelectronic materials and devices. However, this strategy relies on the existence of chemical protocols to prepare highly monodisperse colloids of conjugated polymers in high yields. Here, a recently developed Suzuki–Miyaura dispersion polymerization method is adopted to synthesize core–shell particles, in which a conjugated polymer shell is grown onto non-conjugated organic and inorganic colloidal templates. By chemically anchoring aryl halide groups at the particle surface, a conjugated polymer shell can be attached to a wide variety of organic and inorganic microparticles. In this way, both spherical and non-spherical hybrid conjugated polymer particles are prepared, and it is shown that the method can be applied to a variety of conjugated polymers. This new method offers independent control of the size, shape and photophysical properties of these novel conjugated polymer particles.

Encapsulation and surface charge manipulation of organic and inorganic colloidal substrates by multilayered polyelectrolyte films

Employing layer-by-layer (LbL) technique we could encapsulate both organic and inorganic nano- and microparticulate substrates by multilayer polyelectrolyte films of variable thicknesses. It has been observed that the uniformity of the polyelectrolyte multilayer does not depend severely on the chemical nature of particulate substrate; rather it depends on the initial surface charge density or ζ-potential of their bare surface. Higher ζ-potential of organic albumin nanoparticles helps to keep the polyelectrolyte chains unfolded. On the other hand, a lower ζ-potential of inorganic microparticles such as SiO2 induces a folding of dangling polyelectrolyte chains, forming domains of their aggregates or complexes at the particle surface, making the encapsulating multilayer inhomogeneous.

Flame-retarded hydrophobic cellulose through impregnation with aqueous solutions and supercritical CO2

We have developed flame-retarded hydrophobic cellulose-based materials by producing in situ water-soluble and insoluble inorganic microparticles on various surfaces of native cellulose (filter paper and pure cotton textile). The nanoparticles were produced by simple impregnation of cellulose with two different aqueous solutions followed by a third impregnation with supercritical CO2. Finally, the composite cellulose materials were covered by a silicon-based polymer thin film, to turn it into hydrophobic and prevent the water-soluble particles from absorbing humidity. The obtained flame-retardant behaviour is due to a combination of mechanisms. The total treatment of cellulose has an impact on, both its surface morphology and its hydrophilicity. Thus, the hydrophobic nature of the silicon-based polymer film along with the roughness caused by the presence of the inorganic particles and the inherent roughness of native cellulose resulted in superhydrophobic behaviour. The same process-concept was also applied to regenerated (from newspaper) cellulose with ionic liquids. The produced materials were characterised by thermogravimetric analysis, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy and water contact angle measurements.

Macromol. Rapid Commun. 23/2010

Front Cover: The image presents spherical, cubic, and tetrahedral inorganic microparticles that are used as templates to create hollow polymeric capsules. Anisotropic shapes with well-defined edges can be precisely reproduced using hydrogen-bonded multilayers, fabricated by a layer-by-layer approach. Computational modeling shows that the mechanical stability of the anisotropic capsules is enhanced by the sharp edges and vertices, in contrast to spherical microcapsules that undergo random buckling. Further information can be found in the article by O. Shchepelina, V. Kozlovskaya, E. Kharlampieva, W. Mao, A. Alexeev,* and V. V. Tsukruk* on page 2041.

In vivo internal diffusion of several inorganic microparticles through oral administration

We observed the internal diffusion behavior of inorganic micro/nano particles through oral administration. By oral exposure, the fed particles were absorbed through the digestive system then reached some organs after internal diffusion in the body. For example, TiO2 particles fed to mice were detected in the lung, liver, and spleen after 10 days of feeding. Whereas, the absorption efficiency was extremely low compared with intravenous injection. In a comparison of the simple amount of administration, oral exposure required 102 times or more amount by intravenous injection for detection by an X-ray scanning analytical microscope. During dental treatment, micro/nano particles from tooth or dental materials would generate in the oral cavity, and some of the particles had a possibility to be swallowed, absorbed through the digestive system, and then diffuse into the body. However, our results suggest that biocompatible microparticles that are naturally taken orally affect animals only rarely because of the low absorption efficiency.

Modulation of attractive colloidal interactions by lipid membrane-functionalization

Achieving simple, effective control of interactions between microparticles is an important goal of colloidal science, due both to its widespread technological relevance and its potential to illuminate the fundamental mechanisms governing structure and dynamics in complex fluids. Such control has remained elusive, however, especially with respect to attractive forces between microparticles. The studies described here adopt a biomimetic approach, functionalizing inorganic microparticles with biomolecular membranes. We provide the first reported measurements of the pair interaction energy, the key determinant of colloidal behavior, for such particles. The data demonstrate strong, tunable attractive interactions. Moreover, control of lipid composition enables a striking insight into the long-standing paradox of “like-charge attraction” observed in confined colloidal systems: G. M. Kepler and S. Fraden, Phys. Rev. Lett., 1994, 73, 356–359; D. G. Grier, J. Phys.: Condens. Matter, 2000, 12, A85–A94; M. Polin, D. G. Grier and Y. Han, Phys. Rev. E, 2007, 76, 041406–041407. Decomposing the measured interactions into charge-dependent and -independent terms, we find that the charge-dependent term in the interaction is purely repulsive, while the attraction is independent of particle charge.

Internal Distribution of Several Inorganic Microparticles in Mice

Internal distributions of several inorganic microparticles administered into the tail vein of mice were determined using a Scanning X-ray analytical microscopy and energy-dispersed X-ray spectroscopy. After administration through the tail vein of mice, the particles circulated by blood flow then reach some organs and temporally remained. In this study, we determined that the distribution behaviors in body depend upon the chemical species and the size.

Molecular Design and Fluorescent Whitening Emission from Novel Lanthanide Activated Organic–Inorganic Covalently Hybrid Micro-particles

A series of potential lanthanide activated fluorescent-whitening hybrid micro-particles has been prepared by sol-gel method. The precursor derived from 2,2'-dipyridylamine derivative modified though hydrogen transfer addition exhibited a self-organization under the coordination to RE(3+) (Eu(3+), Tb(3+), Sm(3+), Dy(3+), respectively) evaluated by SEM (micrometric scale) and X-ray diffraction studies (nanometric scale). The adapting traditional routes used in this paper affected the shape of the materials and can be taken as a new method to control the hydrolysis-polycondensation process. Fourier transform infrared (FTIR), Diffuse reflectance ultraviolet-visible spectra (DRUVS) and (1)H NMR spectra were used to confirm the modifications. These activated phosphors with lanthanide ions represent a novel way to produce fluorescent whitening agents.

Oral Transmissibility of Prion Disease Is Enhanced by Binding to Soil Particles

Soil may serve as an environmental reservoir for prion infectivity and contribute to the horizontal transmission of prion diseases (transmissible spongiform encephalopathies [TSEs]) of sheep, deer, and elk. TSE infectivity can persist in soil for years, and we previously demonstrated that the disease-associated form of the prion protein binds to soil particles and prions adsorbed to the common soil mineral montmorillonite (Mte) retain infectivity following intracerebral inoculation. Here, we assess the oral infectivity of Mte- and soil-bound prions. We establish that prions bound to Mte are orally bioavailable, and that, unexpectedly, binding to Mte significantly enhances disease penetrance and reduces the incubation period relative to unbound agent. Cox proportional hazards modeling revealed that across the doses of TSE agent tested, Mte increased the effective infectious titer by a factor of 680 relative to unbound agent. Oral exposure to Mte-associated prions led to TSE development in experimental animals even at doses too low to produce clinical symptoms in the absence of the mineral. We tested the oral infectivity of prions bound to three whole soils differing in texture, mineralogy, and organic carbon content and found soil-bound prions to be orally infectious. Two of the three soils increased oral transmission of disease, and the infectivity of agent bound to the third organic carbon-rich soil was equivalent to that of unbound agent. Enhanced transmissibility of soil-bound prions may explain the environmental spread of some TSEs despite the presumably low levels shed into the environment. Association of prions with inorganic microparticles represents a novel means by which their oral transmission is enhanced relative to unbound agent.

Preparation of various metal-silicate micro-balloons using W/O/W emulsion

Micron-sized inorganic microparticles with hollow insides were prepared by interfacial reaction method, in which an ion exchange reaction between Na+ and metal cations in internal and external aqueous phases, respectively, proceeded through the oil phase involving a cation carrier. The diameter of microballoons was ∼10 µm and shell thickness was below 2 µm. The effects of preparation conditions against the formation of microballoons were examined. The factors examined were metal species in the external aqueous phase and the concentrations of metal chloride and cation carrier. The cross-section of microparticles formed was inspected by scanning electron microscope (SEM) and the inner space of some metal silicates was not hollow but filled-up. The increase of internal and external aqueous solution concentrations caused the increase of diameter and shell thickness of microballoons. Since the penetration of metal cation through the oil phase was promoted by the increase of carrier concentration, the formation of microballoons was completed in a short time of less than 30 min.

Dietary sources of inorganic microparticles and their intake in healthy subjects and patients with Crohn's disease

Dietary microparticles are non-biological, bacterial-sized particles. Endogenous sources are derived from intestinal Ca and phosphate secretion. Exogenous sources are mainly titanium dioxide (TiO2) and mixed silicates (Psil); they are resistant to degradation and accumulate in human Peyer's patch macrophages and there is some evidence that they exacerbate inflammation in Crohn's disease (CD). However, whether their intake differs between those with and without CD has not been studied. We aimed to identify dietary microparticle sources and intakes in subjects with and without CD. Patients with inactive CD and matched general practice-based controls (ninety-one per group) completed 7 d food diaries. Intake data for dietary fibre and sucrose were compared as positive controls. All foods, pharmaceuticals and toothpastes were examined for microparticle content, and intakes of Ca and exogenous microparticles were compared between the two groups. Dietary intakes were significantly different between cases and controls for dietary fibre (12 (SD 5) v. 14 (SD 5) g/d; P=0.001) and sucrose (52 (SD 27) v. 45 (SD 18) g/d; P=0.04) but not for Ca. Estimated median TiO2 and Psil intakes (2.5 and 35 mg/individual per d respectively, totalling 10(12)-10(13) microparticles/individual per d) were broadly similar to per capita estimates and while there was wide variation in intakes between individuals there was no significant difference between subjects with CD and controls. Hence, if exposure to microparticles is associated with the inflammation of CD, then the present study rules out excess intake as the problem. Nonetheless, microparticle-containing foods have now been identified which allows a low-microparticle diet to be further assessed in CD.

Nanoparticle-coated microparticles: preparation and characterization

The objective of the present work was to design and prepare new nanoparticle-coated drug-loaded inorganic microparticles by spray-drying using diclofenac as drug model. Previous works presented the process to dry drug-loaded polymeric nanoparticles using silicon dioxide as adjuvant, otherwise in the present proposition the drug is associated with the silicon dioxide and unloaded polymeric nanocapsule or nanosphere suspensions were used as organic coating. Eudragit S100® was chosen because of its gastric resistance. The potential application of polymeric colloidal suspensions as nanocoating for microparticles were evaluated in terms of process yields, encapsulation efficiencies, morphologic analyses and in vitro drug release profiles in buffered media (pH 1.2; 5.0 and 7.4). The results showed the technological feasibility of preparing controlled nanoparticle-coated drug-loaded inorganic microparticles. When the diclofenac was employed as a hydrophilic model, in this salt form, the powders prepared in two steps (core previously prepared) showed an adequate gastroresistance by the use of Eudragit S100®. The use of diclofenac as a hydrophobic model (acid form) conducted to powders presenting good gastroresistance when the nanocapsules and triacetin were employed.

Matrix Polyelectrolyte Microcapsules: New System for Macromolecule Encapsulation

A new approach to fabricate polyelectrolyte microcapsules is based on exploiting porous inorganic microparticles of calcium carbonate. Porous CaCO3 microparticles (4.5-5.0 microns) were synthesized and characterized by scanning electron microscopy and the Brunauer-Emmett-Teller method of nitrogen adsorption/desorption to get a surface area of 8.8 m2/g and an average pore size of 35 nm. These particles were used as templates for polyelectrolyte layer-by-layer assembly of two oppositely charged polyelectrolytes, poly(styrene sulfonate) and poly(allylamine hydrochloride). Calcium carbonate core dissolution resulted in formation ofpolyelectrolyte microcapsules with an internal matrix consisting of a polyelectrolyte complex. Microcapsules with an internal matrix were analyzed by confocal Raman spectroscopy, scanning electron microscopy, force microscopy, and confocal laser-scanning fluorescence microscopy. The structure was found to be dependent on a number of polyelectrolyte adsorption treatments. Capsules have a very high loading capacity for macromolecules, which can be incorporated into the capsules by capturing them from the surrounding medium into the capsules. In this paper, we investigated the loading by dextran and bovine serum albumin as macromolecules. The amount of entrapped macromolecules was determined by two independent methods and found to be up to 15 pg per microcapsule.

Resonance Raman Scattering from Single Levitated Microparticles

Measurements of resonance Raman scattering from single crystalline (or amorphous) particles suspended in an electrodynamic balance have been made for inorganic and organic microparticles, potassium permanganate (KMnO4) and p-nitrosodimethylaniline ( p-NDMA), respectively. The microparticle dimensions were in the range 10–50 μm. The particles were obtained by evaporating aqueous solution droplets of KMnO4 and p-NDMA (0.01 M concentration) and potassium nitrate or sodium nitrate (1.0 M concentration) added as a nonresonance Raman standard or reference. Resonance Raman spectra were obtained using laser illumination at wavelengths of 514.5 and 488.0 nm. For MnO−4 particles at a laser wavelength of 514.5 nm, the fundamental symmetric stretch mode (ν1) and up to four overtones were observed. In addition, the antisymmetric stretch mode (ν3) and the combination mode (ν1 + ν3) could be seen. In p-NDMA particles, the phenyl-nitroso deformation mode (ν1) and the symmetric benzene ring-stretching mode (ν3) were observed using 488.0 nm laser radiation, but no overtones were distinguishable. As a measure of the morphological variability between particles, the ratio of the intensity of ν1 to the intensity of the largest nitrate ion (Raman) peak (normalized by the concentrations) was determined for each spectrum. This enhancement ratio or reference ratio was of order 100 and varied by 27% for 12 KMnO4 particles with 514.5 nm illumination, by 39% for 10 KMnO4 particles at 488.0 nm, and by 16% for 14 p-NDMA particles at 488.0 nm. Resonance Raman spectra obtained for KMnO4 particles before and after deliquescence indicated that photolysis occurred in the presence of water.

Formation of Ordered Structure in Liquid Phase and Its Use for Materials Design. Control of Polymer Coating Thickness of Microcapsules Containing Inorganic Microparticles Using Cosolvency of Supercritical Carbon Dioxide.

超臨界二酸化炭素とエタノールなどの助溶剤の混合物が混合時にのみ特異的に溶質を溶解する共存効果（コソルベンシー）を利用して，有害な有機溶媒や界面活性剤を使用せずに無機微粒子を内包する数ミクロン～数十ミクロンの高分子マイクロカプセルを形成し，コーティング厚みを制御する方法を提案した．コソルベンシーにより超臨界二酸化炭素中に溶解した被覆用高分子は，急速膨張の後，エタノールなどの助溶媒がポリマーに対して貧溶媒であるので，癒着のない高分子微粒子が得られた．マイクロカプセルの形態・構造は，SEM，TEM，EPMA，ならびに光散乱粒径分布測定装置によって解析した．生成した粒子は，粒径分布が狭い球状粒子であった．マイクロカプセルは，無機微粒子を核としてその周囲に高分子が析出しており，高分子の仕込み組成調製により，マイクロカプセルの高分子コーティング厚みが制御できることを示した．

Inorganic microballoon production from shinju-gan using an entrained bed reactor

Hollow inorganic microparticles were produced continuously from a volcanic glass (shinju-gan or per-lite) using an entrained bed reactor. The microparticles are called expanded perlite. The raw material was a sieved fraction (104 μm in volume average diameter) of crushed perlite, which is from China. The effects of temperature and residence time on expanded perlite yield were investigated.

インテグラシステムの作用と効果

Recently new system of wet-end chemistry to increase retention and drainage of papermaking stock without deteriorating effect on formation has been introduced. The system uses (1) coagulant which acts as neutralization of surface charge of suspended materials, (2) macro-flocculant which acts as bridging fibers and other particles to form large floc, and (3) micro-flocculant which acts as bonding material to form micro-flocculation. Optimization of wet-end chemistry involves selection of best chemicals from the combination of all three agents or of any of the three. ECC International introduced the new concept on wet-end chemistry. Instead of using micro-flocculant which is normally inorganic micro-particles such as bentonite and colloidal silica, formation/drainage aid in the form of ligno-sulphonate is developed as the third component of Integra system. Ligno-sulphonate is used in many industries as dispersant, binder, stabilizer, complexing agent, etc. By selecting right molecular weight and anionic charge density (degree of sulphonation), dramatic effect on drainage and formation was demonstrated with a combination of ultra high molecular weight of cationic polymer flocculant. Several case studies on paper and board machines are presented.