scholarly journals A Gentle Sedimentation Process for Size-Selecting Porous Silicon Microparticles to Be Used for Drug Delivery Via Fine Gauge Needle Administration

Silicon ◽  
2020 ◽  
Author(s):  
Elida Nekovic ◽  
Catherine J. Storey ◽  
Andre Kaplan ◽  
Wolfgang Theis ◽  
Leigh T. Canham
Keyword(s):  
Drug Delivery ◽  
Particle Size ◽  
Porous Silicon ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Agglomeration ◽  
Gas Generation ◽  
Intravitreal Drug Delivery ◽  
Median Diameter ◽  
Experimental Values

AbstractBiodegradable porous silicon (pSi) particles are under development for drug delivery applications. The optimum particle size very much depends on medical use, and microparticles can outperform nanoparticles in specific instances. Here we demonstrate the ability of sedimentation to size-select ultrasmall (1–10 μm) nanoporous microparticles in common solvents. Size tunability is quantified for 1–24 h of sedimentation. Experimental values of settling times in ethanol and water are compared to those calculated using Stokes’ Law. Differences can arise due to particle agglomeration, internal gas generation and incomplete wetting. Air-dried and supercritically-dried pSi powders are shown to have, for example, their median diameter d (0.5) particle sizes reduced from 13 to 1 μm and from 20 to 3 μm, using sedimentation times of 6 and 2 h respectively. Such filtered microparticles also have much narrower size distributions and are hence suitable for administration in 27 gauge microneedles, commonly used in intravitreal drug delivery.

scholarly journals PHYSICOCHEMICAL CHARACTERIZATION OF PROPRANOLOL-LOADED CHITOSAN NANOPARTICLES FOR A BUCCAL DRUG DELIVERY SYSTEM

2020 ◽  
pp. 243-247
Author(s):  
SIRIPORN KITTIWISUT ◽  
PAKORN KRAISIT
Keyword(s):  
Drug Delivery ◽  
Particle Size ◽  
Zeta Potential ◽  
Drug Delivery System ◽  
Delivery System ◽  
Chitosan Nanoparticles ◽  
Particle Sizes ◽  
Zeta Potentials ◽  
Ph Values ◽  
Buccal Drug Delivery

Objective: This study aimed to characterize the physicochemical properties, including pH, zeta potential, and particle size of propranolol-loaded nanoparticles that were incorporated into a buccal transmucosal drug-delivery system. Methods: An ionotropic gelation technique was used to formulate propranolol-loaded chitosan nanoparticles. Chitosan used as the nanoparticle base, using tripolyphosphate (TPP) as a cross-linking agent. The effects on nanoparticle physical properties, including pH, zeta potential, and particle size were examined when various chitosan [0.150-0.300 % (w/v)] and propranolol contents (0-40 mg) were used during the preparation. The effects of using chitosan solutions with different pH values on nanoparticle properties were also determined. Results: The pH values of all nanoparticles ranged between 4.14–4.55. The zeta potentials of the prepared nanoparticles ranged between 22.6–52.6 mV, with positive charges. The nanoparticle sizes ranged from 107–140 nm, which are within the range of suitable particle sizes for transmucosal preparations. Conclusion: The pH values, zeta potentials, and particle sizes of the nanoparticle formulations were influenced by the concentrations of chitosan and propranolol and by the pH of the initial chitosan solution. The relationships between nanoparticle properties and all factors primarily depended on the ionic charges of the components, especially chitosan. Our study provides beneficial physicochemical knowledge for the further development of chitosan-based nanoparticles containing propranolol for buccal drug delivery systems.

Determination of Latex Particle Size Distributions by Fractional Creaming with Sodium Alginate

1961 ◽  
Vol 34 (2) ◽  
pp. 433-445 ◽  
Author(s):  
E. Schmidt ◽  
P. H. Biddison
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Sodium Alginate ◽  
Mass Distribution ◽  
Average Particle Size ◽  
Average Particle ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions

Abstract Knowledge of mass distribution of particle sizes in latex is very important to the latex technologist. Therefore, it is desirable to have available a simple method for the determination of mass distribution of particle sizes. This paper presents a method, based on fractional creaming of latex with sodium alginate, which can be used in any laboratory without special equipment. The method is particularly advantageous for analyzing latexes of very wide particle size distributions. When analyzed with an electron microscope, these latexes require counting a very large number of particles. McGavack found that partial creaming of normal hevea latex with ammonium alginate gives concentrates of larger average particle size than the original latex. He found that the average particle size in the cream approaches that of the original latex as the amount of creaming agent is increased. In a previous paper from this laboratory, Schmidt and Kelsey demonstrated that the phenomenon of fractionation according to particle size with increasing amounts of creaming agent is applicable in a wide variety of anionic latex systems and in colloidal silica. Their results indicated also the existence of a quantitative relationship, independent of the nature of the dispersed particles, between the concentration of creaming agent and size of creamed particles. Maron confirmed fractionation with respect to particle size as a consequence of partial creaming with alginate. He showed that the mass average particle sizes of fractions, determined optically, cumulate to that of the original latex. Although the previous paper by Schmidt and Kelsey implied the basic concept of a method of determining particle size distribution by fractional creaming, it was not exploited at that time. In order to adapt the fractional creaming phenomenon to a quantitative method for particle size determination, we required a more precise knowledge of the relation between creaming agent concentration and size of particles creamed. It was proposed to establish this relationship with the aid of the electron microscope. Various factors influencing the creaming of latex, such as polymer concentration, electrolyte, soap content, and variability of the creaming agent, had to be considered in standardizing the creaming procedure.

Particle Size Characterisation of Tin Oxide (SnO2) Precipitated by Various Techniques: Consistency of Data

2007 ◽  
Vol 561-565 ◽  
pp. 2155-2158
Author(s):  
H. Taib ◽  
Charles C. Sorrell
Keyword(s):  
Particle Size ◽  
Light Scattering ◽  
Tin Oxide ◽  
Spherical Shape ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Oxide Powders ◽  
Spherical Agglomerates ◽  
The Individual

The particle size distributions of tin oxide powders produced from the calcining of precipitated tin oxalate were determined by four methods, these being two static and two dynamic light scattering techniques. Although the individual particle sizes were ~ 75 nm, all of the powders were heavily agglomerated as plates. The non-spherical shape resulted in the following interpretational problems: • None of the measurements was in agreement with any others. • There were very significant disagreements between the two light scattering methods. • The particle size distributions were multimodal. • The main peaks in the distribution curves, which were used to calculate the averages and standard deviations, were not Gaussian. The main uncertainty with these data is associated with the non-spherical agglomerates, which result in the multimodal size distributions. These probably were caused by variable-sized but large platy agglomerates.

Mechanics of Polishing

1998 ◽  
Vol 65 (2) ◽  
pp. 410-416 ◽  
Author(s):  
V. H. Bulsara ◽  
Y. Ahn ◽  
S. Chandrasekar ◽  
T. N. Farris
Keyword(s):  
Particle Size ◽  
Material Removal ◽  
Indentation Hardness ◽  
Particle Sizes ◽  
Size Distributions ◽  
Polishing Process ◽  
Average Force ◽  
Abrasive Particles ◽  
Effect Of Particle Size ◽  
Micro Indentation

A model has been developed to determine the number and sizes of abrasive particles involved in material removal in polishing, and the forces acting on these particles. The effect of particle size on these parameters has been simulated for a range of particle sizes. It is shown that when polishing with abrasive powders having relatively broad size distributions, only a very small percentage of the particles are involved in material removal. Further, these particles are comprised of the larger particles occurring in the tail end of the particle size distribution. The average force on a particle is found to be in the range of 5–200 mN under typical polishing conditions, which is of the order of loads used in micro-indentation hardness testing. These predictions of the model are consistent with observations pertaining to polished surfaces and the polishing process.

Novel Precipitation Route to Silica Grain

1992 ◽  
Vol 271 ◽  
Author(s):  
Barbara Simms ◽  
Tom Gallo
Keyword(s):  
Particle Size ◽  
Acetic Acid ◽  
Aqueous Ammonia ◽  
Sol Gel ◽  
Average Particle ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Small Particles ◽  
High Degree

ABSTRACTWe describe a novel precipitation route to silica grain that lies in the interface between sol-gel and Stöber-type silica. The use of acetic acid as a catalyst for TEOS hydrolysis provides access to a precipitation window in which partially hydrolyzed TEOS and TEOS monomer, when reacted with aqueous ammonia, combine to form pumice-like silica particles in up to 90% yield as SlO2. Precipitated particles exhibit narrow particle size distributions that may be controlled for average particle sizes from 50µ to 400 µ. SEM micrographs show that the particles are agglomerates of small particles, which is consistent with the high degree of observed macroporosity.

scholarly journals Tuning Aerosol Particle Size Distribution of Metered Dose Inhalers Using Cosolvents and Surfactants

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Imran Y. Saleem ◽  
Hugh D. C. Smyth
Keyword(s):  
Particle Size ◽  
Fine Particle ◽  
Laser Diffraction ◽  
Particle Sizes ◽  
Size Distributions ◽  
Metered Dose Inhalers ◽  
Particle Size Distributions ◽  
Metered Dose ◽  
Aerosol Particle Size ◽  
Median Particle

Objectives.The purpose of these studies was to understand the influence of cosolvent and surfactant contributions to particle size distributions emitted from solution metered dose inhalers (pMDIs) based on the propellant HFA 227.Methods.Two sets of formulations were prepared: (a) pMDIs-HFA 227 containing cosolvent (5–15% w/w ethanol) with constant surfactant (pluronic) concentration and (b) pMDIs-HFA 227 containing surfactant (0–5.45% w/w pluronic) with constant cosolvent concentration. Particle size distributions emitted from these pMDIs were analyzed using aerodynamic characterization (inertial impaction) and laser diffraction methods.Results. Both cosolvent and surfactant concentrations were positively correlated with median particle sizes; that is, drug particle size increased with increasing ethanol and pluronic concentrations. However, evaluation of particle size distributions showed that cosolvent caused reduction in the fine particle mode magnitude while the surfactant caused a shift in the mode position. These findings highlight the different mechanisms by which these components influence droplet formation and demonstrate the ability to utilize the different effects in formulations of pMDI-HFA 227 for independently modulating particle sizes in the respirable region.Conclusion. Potentially, the formulation design window generated using these excipients in combination could be used to match the particle size output of reformulated products to preexisting pMDI products.

Effect of bed particle size and temperature variation on the minimum fluidisation velocity: A comparison with minimum fluidisation velocity correlations for bubbling fluidised bed designs

2019 ◽  
Vol 233 (5) ◽  
pp. 1001-1012 ◽  
Author(s):  
Musademba Downmore ◽  
Simbi David Jambgwa ◽  
Kuipa Pardon Kusaziwa
Keyword(s):  
Particle Size ◽  
Temperature Variation ◽  
Good Choice ◽  
Column Height ◽  
Effect Of Temperature ◽  
Internal Diameter ◽  
Particle Sizes ◽  
Fluidised Bed ◽  
Bed Temperature ◽  
Experimental Values

This work presents hydrodynamic studies on the effect of temperature and bed particle variation on minimum fluidisation velocity. A lab-scale bubbling fluidised bed made of stainless steel, with column height of 1 m and internal diameter of 0.15 m was used. Five Geldart-B-type alumina bed materials of mean particle sizes 75, 177, 250, 320 and 500 µm were used and the bed temperature was varied between 50 ℃ and 600 ℃. The hydrodynamic results showed that minimum fluidisation velocity varied directly with mean particle size and inversely with temperature. The pressure drop was found to increase with bed temperature for all the sizes of bed particles. The minimum fluidisation velocity is a key parameter in the design of fluidised bed systems and as such its prediction lies with good choice of correlation. The experimental values were compared with predicted minimum fluidisation velocity from six correlations, with the overall objective of verifying the most suitable correlation. Of the correlations used, the Hartman et al. correlation showed very good fitting with experimental data for beds of 75 and 177 µm particles, and the Mohanta et al. correlation showed good fitting with 250–500 µm bed particles. The models exhibited very good coefficient of multiple determination ( R2), very low fitting errors and low geometric standard deviations across the range of particle sizes and temperature variation. However, the lack of understanding of the parameters such as voidage, particle sphericity, density and viscosity would need more attention, particularly in view of the sensitivity of the minimum fluidisation velocity predictions to these parameters. Further studies are therefore recommended for the verification of the correlations in this regard.

Processing of Optimized Cements and Concretes Via Particle Packing

MRS Bulletin ◽  
1993 ◽  
Vol 18 (3) ◽  
pp. 45-49 ◽  
Author(s):  
D.M. Roy ◽  
B.E. Scheetz ◽  
M.R. Silsbee
Keyword(s):  
Particle Size ◽  
Discrete Systems ◽  
Particle Packing ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Small Particles ◽  
Fresh Material ◽  
Simple Cubic ◽  
Packing Efficiency

It has been well-recognized for many years that the particle-size distributions of the cement and the grading of the aggregates play an important role in determining the properties and characteristics of cement and concrete products. DSP (densified with small particles) type cements and concretes, to a certain extent, MDF (macro-defect-free) cements, and optimized concretes are recently recognized outstanding examples of the application of this principle. The preset characteristics of the cementitious slurry are also strongly influenced by these factors. Both the workability of the fresh material, and the microstructure development are controlled to a considerable extent by these geometric parameters.Two seminal works in the areas of continuous particle size distributions and particle packing are those of Andreason and Furnas, respectively. Furnas deals mainly with discrete systems and Andreason with continuous distributions. As early as 1907, the concept of idealized particle packing was being used to optimize cements and concretes. Figure 1a shows an idealized cross section of a simple cubic packing of monodispersed spheres. This system has a maximum packing density of 0.65%. In an ideally packed system of discrete size ranges, the size of the next smallest particles would be such that they just fit in the gaps between the largest size particles, and so on for subsequent particle sizes; this system is represented schematically in Figure 1b. Not only the sizes but also the relative numbers of particles are important; Figures 1c and 1d show systems where some fraction of the smaller and larger particle sizes, respectively, are missing. Figure 1e shows a system where the size of the second largest particles is too large to fit into the gaps between the largest particles, resulting in a lower packing efficiency. Thus, both the particle size and fractions are important when considering packing efficiency.

scholarly journals Improvement of Ti Processing through Colloidal Techniques

2012 ◽  
Vol 520 ◽  
pp. 335-340 ◽  
Author(s):  
R.G. Neves ◽  
J.A. Escribano ◽  
Begoña Ferrari ◽  
Elena Gordo ◽  
Antonio Javier Sanchez-Herencia
Keyword(s):  
Particle Size ◽  
Sintering Behavior ◽  
Particle Sizes ◽  
Size Distributions ◽  
Colloid Chemistry ◽  
Particle Size Distributions ◽  
Broad Distribution ◽  
Dry Process ◽  
Chemical Physic ◽  
Titanium Powders

The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to prepare Ti powders with small particle size for a better pressing behavior through the spray dry process. The chemical-physic behavior of titanium powders with two different particle size distributions dispersed in water has been studied by measuring the zeta potential as a function of pH, and dispersant concentration. The employment of poly-acrylic dispersants allowed the fabrication of stable slurries with solid contents up to 50 vol% that have been sprayed under different conditions to form agglomerates ranging between 50 and 200 µm. Conditions were selected to achieve spherical agglomerates formed by a broad distribution of particle sizes that shown excellent flowability. Agglomerates were pressed in a uniaxial die to measure the compressibility, showing an improvement in pressing behavior with respect to powders with bigger particle size. The sintering behavior is also improved, as values of 96 % of the theoretical density were obtained for compacts sintered in vacuum at 1100 °C for 30 minutes.

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