Particle Dosage Research Articles

Characteristics of filter cake exfoliation in upward ultrafiltration of nanoparticle suspensions.

Downward and upward ultrafiltration (UF) was performed using the suspensions of nanosized colloidal silica with different particle diameters and their filtration rates were compared. In downward UF, the filtration rate decreases as the particle diameter decreases because the specific filtration resistance of the filter cake becomes significantly higher. In contrast, the filtration rate in upward UF increases with the decrease in the particle diameter because the filter cake consisting of small particles is exfoliated much more easily under the influence of gravity than that of large ones. In order to evaluate the characteristics of the filter cake exfoliation, the steady filtration rate in the upward mode was measured. The steady filtration rate has a tendency to decrease with particle concentration as well as mean particle diameter. Therefore, when the small particles are added into a given concentration of large particle suspension, the mean particle diameter decreases and the total particle concentration increases due to the dosage of small particles. This results in a maximum of the steady filtration rate at a certain dosage of small particles. Moreover, an estimation equation was proposed for predicting the steady filtration rate in upward UF of colloidal silica suspensions with various mean particle diameters and total particle concentrations.

The Immune Toxicity of Titanium Dioxide on Primary Pulmonary Alveolar Macrophages Relies on their Surface Area and Crystal Structure

Surface properties are critical to assess effects of titanium dioxide (TiO2) primary nanoparticles on the immune function of pulmonary alveolar macrophage (PAMs). In this study the immune toxicity of TiO2 primary nanoparticles on PAMs relies on their surface area and crystal structure were determined. The primary PAMs of rats exposed to different sizes and crystal structure of TiO2 particles at different dosages for 24 hrs were evaluated for cytokines, phagocytosis, chemotaxis and surface molecules expression. Nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) level of PAMs significantly increased when exposed to TiO2 primary particles and there were significant association with the exposure total surface area and crystal structure of TiO2 particles in the former. TiO2 particles showed significant inhibiting effects on phagocytotic ability, chemotactic ability, Fc receptors and MHC-II molecular expression of macrophages compared with control. Exposure dosage and crystal structure of TiO2 particles play effects on phagocytotic ability and chemotactic ability of PAMs. These results suggested that TiO2 nanoparticles could induce the release of inflammatory mediators, initiate the inflammation development and inhibit the immune function of PAMs associated with non-specific immunity and specific immunity relies on surface area and crystal structure. NO activity might be a candidate marker indicating the TiO2 exposure burden and cell damage in PAMs.

The adsorptive removal of disinfection by-product precursors in a high-SUVA water using iron oxide-coated pumice and volcanic slag particles

The main objective of this work was to study the effectiveness of iron oxide-coated pumice and volcanic slag particles in removing disinfection by-product (DBP) precursors from a raw drinking water source with high specific UV absorbance (SUVA 254) value. Iron oxide coating of particles significantly increased dissolved organic carbon (DOC) uptakes and decreased DBP formation after chlorination compared to uncoated particles. pH values close to neutral levels during adsorption and chlorination provided DOC, trihalomethane and haloacetic acid reductions around 60–75% employing 6 g/L coated particle dosage. Higher degree of DOC and DBP reductions (>85%) were obtained with increasing particle dose. The uptake of bromide by iron oxide surfaces was negligible and increasing bromide concentrations (up to 550 μg/L) did not negatively impact the DOC uptake. However, due to competition between natural organic matter (NOM) and bicarbonate for the iron oxide surfaces, increasing bicarbonate alkalinity levels reduced DOC uptakes. Overall, the results indicated that the iron oxide-coated pumice/slag particles are effective adsorbents to remove NOM and control DBP formation in waters with relatively high DOC and SUVA 254 levels. However, they may not be effective for waters with alkalinity levels above 250 mg CaCO 3/L.

Microstructure and properties of cement mortars containing organo-modified reservoir sludge

Reservoir sludge can be organo-modified by a cation-exchange reaction and then employed as a substitute for a portion of fine aggregates in cement mortars. The chemical structure and properties of organo-modified reservoir sludge (OMRS) were first analyzed by conducting a series of TGA, FTIR, EDS and XRD measurements. The microstructures of cement mortars containing different amounts of OMRS particles were then characterized by using MIP, EDS and a water contact angle goniometer. In addition, the effects of OMRS particles on the compressive strength and permeability of cement mortars were evaluated. Experimental results indicate that the hydrophobic OMRS particles randomly distributed in cement mortars contribute to the decrease in capillary porosity and the increase in water diffusion barriers. As a result, an adequate dosage of OMRS particles to give a higher compressive strength and a lower permeability ratio for cement mortars is proposed here.

Ferromagnetic Nanoparticles Dose Based on Tumor Size in Magnetic Fluid Hyperthermia Cancer Therapy

The interest in magnetic fluid hyperthermia (MFH) and cancer therapy has noticeably increased in the last years. At present, a successful realization of this interdisciplinary research is hampered by some unsolved problems. One of these problems this paper intended to clarify is how to find an estimate of the appropriate dosage of magnetic nanoparticles that injected into the tumor would help achieve an optimum temperature of 42degC, thus resulting in an increase of the susceptibility for apoptosis in tumor cells. We created a computational model in COMSOL: Multiphysics in order to analyze the heat dissipation within the tumor tissue. By considering various types of tissues with their respective physical and physiological properties (breast, liver, and skin tissues) and also by taking into account the amount of heat generated through the Brownian rotation and the Neel relaxation, it has been studied the tumor border temperature achieved for various concentrations of magnetic nanoparticles in their superparamagnetic behavior. Distinct simulations of a spherical tumor located in a cubical region of a volume of 1.2-3.5 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> within the tissue were designed. We performed a systematical variation of tumor diameter and particle dosage for every physical parameter of above mentioned tumor tissues (e.g., tissue density, tumor/tissue perfusion rate). By this systematization we intended to understand the interdependence of these parameters and their effects on hyperthermia therapy.

Mesoporosity and Functional Group Dependent Endocytosis and Cytotoxicity of Silica Nanomaterials

We report different mesoporosity-dependent and functional group-dependent cytotoxicity and endocytosis of various silica nanomaterials on suspended and adherent cells. This dependency further varied with incubation time and particle dosage, and appeared to be associated with the particles' endocytotic efficiency and their chemical and physical properties. We studied two common mesoporous nanomaterials (MSNs), MCM-41 and SBA-15, and one type of solid-cored silica microsphere, paralleled by their quaternary amine functionalized counterparts. Compared to SBA-15, MCM-41 has a larger surface area but smaller pore size, whereas SMS exhibits low surface area and poor porosity. In Jurkat cells, SBA-15 and MCM-41 exhibited different cytotoxicity profiles. However, no significant cell death was detected when treated with the aminated MSNs, indicating that the positively charged quaternary amines prevented cellular injury from mesoporous nanoparticles. Furthermore, the effective internalization of MSN but not aminated-MSNs was clearly observed, in line with their consequent cytotoxicity. SK-N-SH (human neuroblastoma) cells were found to be more resistant to the treatment of MSN, whether aminated or not. Incubation with either SBA-15 or MCM-41 over time showed a recovery in cell viability, while exposure to MSN-N particles did not induce a noticeable cell death until longer incubation with high dosage of 200 microg/mL was applied. Both aminated and nonaminated silica spheres exhibited instant and constant toxicity on Jurkat (human T-cell lymphoma) cells. TEM images revealed successful endocytosis of SMS and SMS-N, although SMS-N appeared to accumulate more in the nucleus. For SK-N-SH cells, low dosage of SMS was found to be less toxic, whereas high dosage produced profound cell death.

Study of the Optimum Injection Sites for a Multiple Metastases Region in Cancer Therapy by Using MFH

Metastases represent the final stage in cancer progression. Their early diagnosis and appropriate treatment are very important in order to maintain a high survival prognostic. The interest in MFH (magnetic fluid hyperthermia) and cancer therapy has noticeably increased in the last years. There are still numerous problems that need to be solved before a clinical model may be tested. The goal of this paper is to both quantify the optimum dose of magnetic material and optimize injection sites in order to achieve a therapeutic temperature of 42degC that may induce apoptosis in tumor cells. A successful realization of this therapy implies a heating zone of at least 2 mm around the tumor. finite element method (FEM) simulations of spherical metastases in liver and breast tissues near a blood vessel were performed using COMSOL multiphysics (heat transfer module) in order to simulate the temperature field produced by ferromagnetic nanoparticles within the tumor and healthy tissues. A systematical variation of tumor diameter and particle dosage was performed for every physical parameter for the tumor tissues mentioned above (e.g., tissue density, tumor/tissue perfusion rate) in order to understand the interdependence of these parameters and their effects on hyperthermia therapy.

Bismuth recovery from acidic solutions using Cyphos IL-101 immobilized in a composite biopolymer matrix

Impregnated resins prepared by the immobilization of an ionic liquid (IL, Cyphos IL-101, tetradecyl(trihexyl)phosphonium chloride) into a composite biopolymer matrix (made of gelatin and alginate) have been tested for recovery of Bi(III) from acidic solutions. The concentration of HCl slightly influenced Bi(III) sorption capacity. Bismuth(III) sorption capacity increased with IL content in the resin but non-linearly. Maximum sorption capacity reached 110–130 mg Bi g −1 in 1 M HCl solutions. The mechanism involved in Bi recovery was probably an ion exchange mechanism, though it was not possible to establish the stoichiometric exchange ratio between BiCl 4 − and IL. Sorption kinetics were investigated through the evaluation of a series of parameters: metal concentration, sorbent dosage, type and size of sorbent particles and agitation speed. In order to reinforce the stability of the resin particles, the IL-encapsulated gels were dried; this may cause a reduction in the porosity of the resin particle and then diffusion limitations. The intraparticle diffusion coefficients were evaluated using the Crank's equation. Additionally, the pseudo-first-order and pseudo-second-order equations were systematically tested on sorption kinetics. Metal can be desorbed from loaded resins using either citric acid or KI/HCl solutions. The sorbent could be recycled for at least three sorption/desorption cycles.

A new method for quantifiable and controlled dosage of particulate matter for in vitro studies: The electrostatic particulate dosage and exposure system (EPDExS)

An exposure chamber is described for the quantifiable addition of fine and ultrafine aerosol particulate matter directly to cells and used to demonstrate the in vitro cytotoxicity of fine 1,4-naphthoquinone particles to murine lung epithelial cells. The electrostatic particulate dosage and exposure system (EPDExS) operates on the principle of electrostatic precipitation and is shown to deposit fine and ultrafine aerosol particles directly to cells with 100% efficiency for particle diameters in the range of 40-530nm. This range is not limited by the EPDExS, but rather by the aerosolization method used for this study. Numbers of particles deposited onto the cells are counted with a condensation particle counter, negating any need to calculate or estimate particle exposure. The process of particle introduction, assessed using Trypan blue dye exclusion, had no effect on cell viability. In combination with a differential mobility classifier, the EPDExS can deliver select particle diameters to cells. The ability to control the diameter and number of particles deposited permits in vitro toxicity studies of particulate matter using different particle dosage metrics, i.e., particle number and size, surface area and mass. Finally, because EPDExS introduces particles directly from the aerosol, it can be used to expose cells grown at air/liquid interfaces.

Influence of Size, Surface, Cell Line, and Kinetic Properties on the Specific Binding of A33 Antigen-Targeted Multilayered Particles and Capsules to Colorectal Cancer Cells

There has been increased interest in the use of polymer capsules formed by the layer-by-layer (LbL) technique as therapeutic carriers to cancer cells due to their versatility and ease of surface modification. We have investigated the influence of size, surface properties, cell line, and kinetic parameters such as dosage (particle concentration) and incubation time on the specific binding of humanized A33 monoclonal antibody (huA33 mAb)-coated LbL particles and capsules to colorectal cancer cells. HuA33 mAb binds to the A33 antigen present on almost all colorectal cancer cells and has demonstrated great promise in clinical trials as an immunotherapeutic agent for cancer therapy. Flow cytometry experiments showed the cell binding specificity of huA33 mAb-coated particles to be size-dependent, with the optimal size for enhanced selectivity at approximately 500 nm. The specific binding was improved by increasing the dosage of particles incubated with the cells. The level of specific versus nonspecific binding was compared for particles terminated with various polyelectrolytes to examine the surface dependency of antibody attachment and subsequent cell binding ability. The specific binding of huA33 mAb-coated particles is also reported for two colorectal cancer cell lines, with an enhanced binding ratio between 4 and 10 obtained for the huA33 mAb-functionalized particles. This investigation aims to improve the level of specific targeting of LbL particles, which is important in targeted drug and gene delivery applications.

Bi-modal hetero-aggregation rate response to particle dosage

The rate of flocculation of cationic polystyrene latex (PSL) particles by smaller, anionic PSL particles has been measured using a low-angle static light scattering technique. The rate of aggregate growth has been investigated as a function of particle size ratio and relative concentration of each particle species (for a constant dose of cationic particles). Contrary to many previous reports, two peaks in the flocculation rate were observed as a function of dose. It is speculated that the peak observed at the lower particle concentration coincides with the dose yielding maximum constant collision efficiency in the steady-state regime, a condition which is attained only after complete adsorption of the smaller particles onto the larger particle species. The peak at the higher particle concentration is believed to be related to the maximum collision rate constant upon reaching the steady-state regime, the value of which corresponds to maximum degree of aggregation and therefore the maximum mean collision efficiency prior to reaching this condition. From classical collision kinetics, the rate of aggregate growth may be represented as being proportional to the product of the collision rate constant and collision efficiency at any given time. Given then that the maximum value of these two variables coincides with different particle concentrations, the product of the response of each to particle dosage can in some cases yield a net bi-modal aggregation rate response to particle dosage.

Reduction of Nitrogen on Gallium Phosphide Nanoparticles

Abstract Under mild ambient conditions gallium phosphide (GaP) nanoparticles were employed to carry out the reduction of nitrogen. By using Nessler's reagent ammonia was detected in the slurry where the aggregated GaP particles were suspended in water and bubbled by pure nitrogen. Dependence of the concentration of ammonia upon bubbling time, velocity of the flow of nitrogen, and dosage of GaP particles was investigated. In comparison with the original GaP nanoparticles, the Raman scattering of the GaP particles undergoing the process of nitrogen fixation reveals that two sharp lines at 138 and 182 cm‐1, respectively, emerged from the broad continuum around 100–200 cm‐1. These two lines might be assigned to the translational motions of ammonia adsorbed on the surface of the GaP particles. An assessment of the infrared spectra of the two GaP particles led to the conclusion that the environment of the two H2O molecules was not identical. Analysis of the electron spin resonance results showed that the structure defect, gallium self‐interstitial, was not involved in the nitrogen fixation of the GaP nanoparticles.

Dechlorination of Hexachlorobenzene by Zero-Valent Iron

Chemical reduction of hexachlorobenzene (HCB) by metallic iron was investigated. Since the percentage of HCB transformation is almost the same as that of chloride ion production, no chlorinated intermediates in the solution was formed during the reduction reaction. The solution pH went to around 8.0 even though the initial pH was 10 or lowered to 3. The reaction is pseudofirst order with respect to HCB concentration. The optimum dosage of iron particles for the dechlorination of HCB varies with the HCB concentration. For example, when the initial concentration of HCB was 1.0×10-5 M, the highest transformation rate of HCB occurred with using at 350 g/L of iron particles; the optimum dosage shifted to around 500 g/L when the HBC concentration was 2.72×10-5 M.

Direct and indirect induction of apoptosis in human mesenchymal stem cells in response to titanium particles

The most frequent complication of total joint arthroplasty is periprosthetic osteolysis initiated by an inflammatory response to orthopaedic wear debris, which if left untreated, can result in implant instability and failure, eventually requiring revision surgery. We have previously reported that osteogenic differentiation of human marrow stroma-derived mesenchymal stem cells (hMSCs) is suppressed upon exposure to titanium particles, accompanied by reduced bone sialoprotein (BSP) gene expression, diminished production of collagen type I and BSP, decreased cellular viability and proliferation, and inhibition of extracellular matrix mineralization. In this study, we have further investigated hMSC cytotoxicity upon exposure to submicron particles of commercially pure titanium (cpTi) and zirconium oxide (ZrO 2). Our results showed that direct exposure to cpTi and ZrO 2 particles compromises cell viability through the induction of apoptosis, eliciting increased levels of the tumor suppressor proteins p53 and p73, in a manner dependent on material composition, particle dosage, and time. Additionally, conditioned medium collected from hMSCs exposed to cpTi particles, but not to ZrO 2 particles, is cytotoxic to hMSCs, inducing apoptosis in the absence of particles. These findings demonstrate that exposure to orthopaedically derived wear particles can compromise hMSC viability through the direct and indirect induction of apoptosis. Thus, prolonged in vivo exposure of marrow-derived hMSCs to implant-derived wear debris is likely to reduce the population of viable osteoprogenitor cells, and may contribute to poor periprosthetic bone quality and implant loosening.

パーティクルとＤＤＳ 脂質パーティクル製剤

Particle dosage forms have been receiving much attention in drug delivery systems because of such features as controlled release, absorption improvement and drug targeting. In addition, unlike polymer drugs and prodrugs, particles have the advantage of ability to carry many drug molecules. Most particle formulations have been designed to reduce toxicity and to increase accumulation at target sites, to some extent being used for in a number of clinical applications. Especially lipid-based particles such as liposomes, emulsions and solid particles composed of lipids (solid lipid particles, SLN) have been focused on use for drug delivery systems. Currently, Lipid-based particles are mostly used for controlled release of drugs, whereas cationic liposomes and emulsions are used as vectors for gene delivery. The introduction of polyetyleneglycol derivative (PEG) to lipids, i. e. “PEGlated” as long-circulating liposomes and the “remote loading” method for drug loading into the liposomes has produced liposome-encapsulated drugs for chemotherapy. PEGlated technique has also been applied to injectable microemulsions and solid lipid particles. The area of liposome targeting, e. g. use of antibody-targeting liposomes, has been extensively studied. In gene delivery, the role of helper lipids such as cholesterol and DOPE as well as that of PEG lipids in cationic liposomes in improving transfection efficiency in vivo has been reported. The study of drug distribution in particles, and design of particles targeted at tissues and cells with ligands and biosenser induced to nucleus are needed for the clinical use of lipid-based particles.

高吸水性ゲル粒子を利用したタンパク質溶液の濃縮脱塩

We quantitatively investigated a process for concentrating and desalinating bovine serum albumin (BSA) in potassium chloride solution by multi-stage operation with superabsorbent-crosslinked hydrogels. The process employs swelling of gel particles by the absorption of water and electrolyte with exclusion of protein molecules. In the two-stage operation, the concentrated solution was diluted with water, and then other gels were added to the diluted solution in order to further concentrate the protein. As a result, the solution was effectively concentrated and desalinated with the superabsorbent hydrogels, and the characteristics of concentration and desalination of a protein solution by multi-stage operations are well expressed by the swelling behavior of superabsorbent hydrogels for a variety of electrolyte concentrations. Furthermore, the optimum dosage of gel particles in each stage was also determined.

In vitro response of human fibroblasts to commercially pure titanium.

The generation of metal particles through surface wear of prosthetic joints has been associated with biological reactions that may lead to prosthetic component loosening. The role of the macrophage in these reactions has been studied extensively, but that of the fibroblast has not. The few fibroblast studies that there have been have shown that particles of several metals, with sizes over a wide range, can promote cytokine release and may cause cell necrosis. The intent of this study was to determine if there are metal particle exposure threshold levels that result in morphological changes and cell necrosis of fibroblasts in peri-articular tissues. Retrieved human fibroblasts (superior medial plica) were cultured in standard fashion and then were exposed to various particle dosages of commercially pure Titanium (cpTi). Cell morphological changes and necrosis were observed to occur when the total mass of the particle dosage exceeded a threshold level. These data imply that these cell responses occur at threshold levels of wear particle exposure.

Kinetics of Adsorption of Pb (II) on Used Tea Leaves and Cr (VI) on Acacia Arabica Bark

AbstractAdsorption of Pb (II) on used tea leaves and Cr (VI) on acacia arabica bark after chemical pretreatment exhibit nearly first‐order reversible reaction kinetics in wastewater treatment. Adsorption follows Langmuir and Freundlich isotherm models. Effective parameters such as initial metal‐ion concentration, adsorption dosage, and size of adsorbent particles have been correlated to enable prediction of the equilibrium adsorption of metal ions within a maximum deviation of ± 10% from experimental data.

Dispersion of aerial agricultural sprays; model and validation

A model has been developed to calculate the dosages of airborne pesticide particles in the downwind area during aerial crop spraying. The model is valid for crosswind flying, small flying heights (∼2 m) and formulations consisting of an involatile pesticide or a combination of an involatile pesticide and a volatile carrier liquid (e.g. water). The model consists of two submodels: a model which describes the development of a pair of initial clouds, mainly owing to the action of the aircraft-induced vortices, and a model which describes the atmospheric dispersion of this pair of initial clouds. The model was validated by means of the results of field experiments carried out by R.S. Crabbe and M. McMooeye. Two formulations were applied during the field trials performed by these researchers: an oil in water emulsion (six trials) and a wettable powder (three trials). The agreement between the calculated and measured dosages was good in the case of the experiments with the oil in water emulsion, especially with respect to the horizontal dosage profile (height 1.5 m; downwind distances up to 500 m). However, the agreement was moderate with respect to the vertical dosage profile (heights up to 20 m) at a distance of 200 m. The agreement between the calculated and measured dosages for the experiments with the wettable powder formulation was poor. It was shown by means of a sensitivity analysis that the influence of the particle size distribution of the emitted spray on the calculated dosage of the airborne pesticide particles is very large.

Carcinogenic risk assessment criteria associated with inhalation of airborne particulates containing chromium(VI/III)

Contaminated land sites and unused chromate production facilities raise the possibility that remediation operations could involve generation of airborne particles of respirable size containing both Cr(VI) and Cr(III) in soluble and insoluble forms. These airborne particles, reaching human populations in the neighborhoods involved, can pose carcinogenic risks via Cr(VI)-containing material retained in the lungs. It is proposed that the risk assessment process for this inhalation exposure be governed by the following considerations. (i) Only the respirable fraction (0.2–10.0 μm diameters) of the inhaled particulates should be considered as contributing to delivered dosage of Cr(VI) to the lung. (ii) In accordance with the ICRP analysis of particulate retention in the lung for extended intervals, the airborne respirable particle intake should be multiplied by the factor 0.125 to generate an estimate of dosage of particles retained in the lung for extended intervals, leading to possible carcinogenesis from the Cr(VI) content. And (iii), the inhalation carcinogenic risk for Cr(VI) should only be modelled in increments above a daily total chromium intake of 100 μg per day, a current estimate of the required daily intake of this essential mineral.