Stability Studies on Colloidal Suspensions of Polyurethane Nanocapsules

2006 ◽  
Vol 6 (9) ◽  
pp. 3187-3192 ◽  
Author(s):  
K. Bouchemal ◽  
S. Briançon ◽  
F. Couenne ◽  
H. Fessi ◽  
M. Tayakout
Keyword(s):  
Aqueous Phase ◽  
Uv Irradiation ◽  
Active Drug ◽  
Physical Stability ◽  
Colloidal Suspensions ◽  
Polymeric Membrane ◽  
Colloidal System ◽  
Size Change ◽  
Spontaneous Emulsification ◽  
External Agents

Generally nanocapsules suspensions are a colloidal system in a metastable state, there is aggregation due to attraction and repulsion forces between particles. The objective of this work was to bring the role of the polymeric membrane in the protection of the active drug against damaging caused by external agents and to select the monomer which leads to obtain stable formulation with the highest possible payload of the active drug. The stability testing involving visual aspect, particle size measurement, transmission electron microscopy (TEM) examination, and drug loss was conduced after 6 months of storage at different temperatures (4, 25, and 45 °C). The colloidal suspensions of nanocapsules were obtained using the combined interfacial polycondensation and spontaneous emulsification, the technique was used to encapsulate α-tocopherol using polyurethanes polymers. It is a one step procedure: An organic phase composed of a water miscible solvent (acetone), lipophilic monomer (Isophorone diisocyanate IPDI), oil, and a lipophilic surfactant, is injected in an aqueous phase containing hydrophilic monomer (diol with various molecular weight: 1,2-ethanediol (ED), 1,4-butanediol (BD), and 1,6-hexanediol (HD)) and hydrophilic emulsifying agent. The water miscible solvent diffuses to the aqueous phase, the oil precipitates as nano-droplets, and the two monomers react at the interface, forming a membrane around the nanoemulsion leading to nanocapsules. A good physical stability of suspensions corresponds to absence of symptoms such as sedimentation or agglomeration, significant size change and α-tocopherol degradation due to external agents such as oxygen, temperature, and ultraviolet (UV) irradiation. The size of nanocapsules before storage was about 232±3, 258±29, and 312±4 nm for ED, BD, and HD, respectively. After 6 months of storage, polyurethanes nanocapsules possess good stability against aggregation at 4 and 25 °C. Comparing results obtained using different monomers, it reveals that the polyurethane based on HD offers good protection of α-tocopherol against damaging caused by the temperature and UV irradiation.

Transformation of Aggregated C60in the Aqueous Phase by UV Irradiation

2009 ◽  
Vol 43 (13) ◽  
pp. 4878-4883 ◽  
Author(s):  
Jaesang Lee ◽  
Min Cho ◽  
John D. Fortner ◽  
Joseph B. Hughes ◽  
Jae-Hong Kim
Keyword(s):  
Aqueous Phase ◽  
Uv Irradiation

Simulation of the Chemical Influences to the Polishing Process of Optical Glasses

2008 ◽  
Vol 39-40 ◽  
pp. 293-298
Author(s):  
Elisabeth Becker ◽  
Andreas Prange ◽  
Reinhard Conradt
Keyword(s):  
Chemical Composition ◽  
Thermodynamic Parameters ◽  
Aqueous Phase ◽  
Fluid Phase ◽  
Colloidal System ◽  
Polishing Process ◽  
Optical Glasses ◽  
Solubility Products ◽  
The Stability ◽  
The Impact

In the last step of fabrication, optical and fine-optical glasses are polished to fulfill the optical requirements for their surfaces. The major influences on the process are caused by the mechanics of the polishing machine, by the chemistry (composition of the glass, as well as the polishing suspension of water and polishing grains, CeO2) [1], [2] and by the material and structure of the polishing pad. From previous own results [3], [4] it is known that the stability of the colloidal system has a major impact on the polishing results and that it is influenced by matter from the glass removal. Thus the glasses have been classified in glass families, depending on their chemical composition and their mutual compatibility in the process. As it is not always possible to measure this compatibility, the impact of the various dissolved glass ions in the fluid phase of the polishing suspension is simulated by the use of thermodynamic parameters. Therefore the specific solubility products in the aqueous phase are modeled (using, e.g., the software HSC) comprising steady accumulation of ions from the glass removal. With this simulation, the examination of the chemical part of the chemo-mechanical polishing process will be concluded.

Degradation of PVDF-based composite membrane and its impacts on membrane intrinsic and separation properties

2016 ◽  
Vol 36 (3) ◽  
pp. 261-268 ◽  
Author(s):  
Mei Jiun Lee ◽  
Chi Siang Ong ◽  
Woei Jye Lau ◽  
Be Cheer Ng ◽  
Ahmad Fauzi Ismail ◽  
...  
Keyword(s):  
Uv Irradiation ◽  
Exposure Time ◽  
Composite Membrane ◽  
Polyvinylidene Fluoride ◽  
Uv Light ◽  
Irradiation Time ◽  
Uv Exposure ◽  
Polymeric Membrane ◽  
Permeate Flux ◽  
Wastewater Treatment Process

Abstract In this work, an attempt was made to evaluate the effects of ultraviolet (UV) irradiation period on the intrinsic and separation properties of composite membrane composed of organic polyvinylidene fluoride and inorganic titanium dioxide (TiO2) nanoparticles by exposing the membrane to UV-A light for up to 250 h. The changes on membrane structural morphologies and chemical characteristics upon UV exposure were studied by field-emission scanning electron microscope and Fourier transform infrared, respectively. It was observed that some cracks and fractures were formed on the membrane outer surface when it was exposed to 120-h UV light. Further increase in UV irradiation time to 250 h had caused membrane structure to collapse, turning it into powder form. Filtration experiments showed that the permeate flux of irradiated membrane was significantly increased from 10.89 L/m2 h to 21.84 L/m2 h (>100% flux increment) while oil rejection decreased with increasing UV exposure time from 0 h to 120 h. Furthermore, the mechanical strength and thermal stability of irradiated membrane were also reported to decrease with increasing UV exposure time, suggesting the negative impacts of UV light on the membrane overall stability. This research is of particular importance to evaluate the suitability and sustainability of polymeric membrane, which is widely considered as the host for photocatalyts and used for wastewater treatment process under UV irradiation.

Nanoparticles for Drug Delivery: Review of the Formulation and Process Difficulties Illustrated by the Emulsion-Diffusion Process

2006 ◽  
Vol 6 (9) ◽  
pp. 2664-2681 ◽  
Author(s):  
D. Moinard-Checot ◽  
Y. Chevalier ◽  
S. Briançon ◽  
H. Fessi ◽  
S. Guinebretière
Keyword(s):  
Drug Delivery ◽  
Diffusion Process ◽  
Process Development ◽  
Colloidal Suspensions ◽  
Polymeric Membrane ◽  
Physical Mechanisms ◽  
Pharmaceutical Application ◽  
Simple Scaling ◽  
Soft Particles

The elaboration of nanoparticles aqueous suspensions aimed at the drug delivery and related process development appear as difficult tasks, due to specificities related to the nanometric size. Such small sizes are required for specific applications in pharmacy. The switch of micrometric to nanometric field represents an actual challenge and cannot be considered as a simple scaling-down of chemical engineers. Ideas and concepts developed first in nanosciences have been adapted to the pharmaceutical application in drug delivery. In spite of drastic constraints due to pharmaceutical application, some parameters allow the control. A brief and not exhaustive review of the state-of-the-art on polymer particles used in the drug delivery field is presented. Attention was more particularly paid on preparation processes and their constraints by describing advantages and drawbacks of each process. The adaptation to the pharmaceutical field, the difficulties and pitfalls which are shared, with most research works in nanoscience, are illustrated thanks to our own results on nanocapsules obtained by "emulsion-diffusion" process presented as a case-study. Thanks to these results, we illustrate the peculiar features and difficulties encountered regarding nanocapsules preparation and characterization. Indeed, such a process allows to prepare nanocapsules of few hundreds nanometers diameter having an oil core surrounded by a polymeric membrane. The characterization of such soft particles colloidal suspensions is often difficult and involves heavy investigation techniques in order to highlight physical mechanisms leading to the nanocapsule properties. This is a key step regarding the final properties as a drug delivery system.

scholarly journals Preparation, Characterization and Biological Efficacy of Eucalyptus Oil Nanoemulsion against the Stored Grain Insects

2020 ◽  
pp. 41-51
Author(s):  
Tahany G. M. Mohammed ◽  
M. E. H. Nasr
Keyword(s):  
Control Strategies ◽  
Physical Stability ◽  
Sitophilus Oryzae ◽  
Contact Toxicity ◽  
Fumigant Toxicity ◽  
Stored Grain ◽  
Spontaneous Emulsification ◽  
Eucalyptus Oil ◽  
Rhizopertha Dominica ◽  
Stored Grain Insects

Nanotechnology has enormous potential for developing alternative pest control strategies and reducing the risk of insecticide molecules. The present study aimed to develop a stable nanoemulsion (NE) of eucalyptus oil (EO) by the spontaneous emulsification method and evaluate its insecticidal and repellent effect against Sitophilus oryzae (L.), Rhizopertha dominica (F.) and Tribolium-castaneum (Herbst.). The prepared nanoemulsion formulation having a small particle size 8.57 nm with polydispersity index (PDI) 0.28. The study of the stability and physicochemical properties showed that the prepared formulation had good physical stability without any change in the macroscopic parameters. In addition, results showed that theinsecticidal activity of the prepared NE was higher than the original EO against the three tested insect speciesand the mortality increased with increasing concentrations and extending of exposure time. The contact toxicity of NE film revealed that, adults of R. dominica was more susceptible to all treatments followed by S. oryzae adults, while adults of T. castaneum was the least susceptible one, however, adults of S. oryzae was more susceptible followed by T. castaneum adults while, adults of                    R. dominica was the least susceptible one according to the fumigant toxicity and repellency. Our results suggested that the prepared formulation may be used in an integrated pest managementprogramfor controlling stored grain insects.

scholarly journals Stability of a colloidal system based on avocado (Persea americana Mill. cv. Hass) and others: Effect of process and composition

2017 ◽  
Vol 66 (3) ◽  
pp. 338-346
Author(s):  
Eliana María Estrada Mesa ◽  
Misael Cortés Rodríguez ◽  
Guillermo Antonio Correa Londono
Keyword(s):  
Physical Stability ◽  
Stability Index ◽  
Persea Americana ◽  
System Stability ◽  
Colloidal System ◽  
Drying Process ◽  
Homogenization Time ◽  
Central Composite Experimental Design ◽  
Nutritional Benefits ◽  
Potential Use

Avocado (Persea americana Mill. cv. Hass), is a perishable fruit, which compositionally presents nutritional benefits, which has led to its productive chain to look for new alternatives of agroindustrialization to improve its competitiveness in the market, being guacamole a potential option. The aim of this research was to evaluate the influence of composition and homogenization process on the colloidal system stability based on avocado and other ingredients for a potential use in the aspersion drying process. We used the surface response methodology and a central composite experimental design for experimental optimization of the process, considering three independent variables as follows: avocado dry solids (DSavocado), homogenization time and tert-butylhydroquinone concentration (TBHQ), and six dependent variables: zeta potential (-ζ), color (L *: brightness, a *: green-red chromaticity, b *: yellow-blue chromaticity), viscosity (μ), spectral absorption stability index, peroxide index (PI) and particle size (D10, D50 and D90). The best emulsion and process formulation was achieved with 47.1% of DSavocado, 5 min of homogenization and 100 mg.kg-1 of TBHQ, obtaining an emulsion with -ζ = -27.67 ± 0.29, L * = 51.3 ± 1.0, a * = -5.8 ± 0.8 and b * = 30.0 ± 1.9, μ = 1034.56 ± 95.91 cP , R = 0.78 ± 0.03, IP = 0.73 ± 0.30 meq H2O2.Kg-1 emulsion, D10 = 8.1 ± 0.7 μm, D50 = 56.2 ± 11.5 μm and D90 = 346.6 ± 94.6 μm. The emulsion based on avocado and other ingredients, presents a physico-chemical, physical stability adequate stability, which guarantees a potential use for aspersion-drying process, since it meets with the criteria design for viscosity and total solids, of the pilot unit PSALAB, Vibrasec S.A.

scholarly journals Thermosensitive Brinzolamide in situ Gel Nanoemulsions, in vitro and ex vivo Evaluation

2020 ◽  
Vol 11 (1) ◽  
pp. 7754-7764
Keyword(s):  
Carbonic Anhydrase ◽  
Ex Vivo ◽  
Physical Stability ◽  
Topical Administration ◽  
Physicochemical Characteristics ◽  
Spontaneous Emulsification ◽  
In Situ Gel ◽  
Physicochemical Features

Brinzolamide (BZ) is a carbonic anhydrase inhibitor with selectivity and affinity for the carbonic anhydrase type II isoenzyme that administrated topically as an ophthalmic suspension for reducing intraocular pressure. In this study, BZ in situ gel nanoemulsions (NEs) were developed and evaluated for transcorneal permeation via the bovine corneal membrane. The spontaneous emulsification method was employed to prepare BZ in situ gel NEs. Various physicochemical characteristics, including particle size, polydispersity index, pH, refractive index, and viscosity, were evaluated. Accelerated physical stability and in vitro drug release, as well as transcorneal permeation studies was performed by applying the Franz-type diffusion cells. Thermosensitive BZ in situ gel NEs with desired physicochemical features and sustained release profiles were designed in the current study. Optimized Formulations exhibited physical stability under different conditions. The transcorneal permeation of formulations was higher than that of suspension, especially for F3b formulation. According to the present in vitro and ex vivo evaluations, it is concluded that in situ gel NEs could be a topical administration of BZ as a suitable ocular drug delivery system.

scholarly journals Microemulsion Stability of Virgin Coconut Oil Based on Tradition of Melala Sumbawa's Society

2021 ◽  
Vol 4 (2) ◽  
pp. 120-126
Author(s):  
Devi Ayu Septiani ◽  
Jono Irawan ◽  
Hermansyah Hermansyah ◽  
Yayuk Andayani
Keyword(s):  
Laboratory Experiments ◽  
Physical Stability ◽  
Coconut Oil ◽  
Coconut Milk ◽  
Colloidal System ◽  
Virgin Coconut Oil ◽  
Colloid System ◽  
Oil In Water ◽  
Isolation Methods ◽  
The Stability

The Melala is a tradition of the Sumbawa people who use coconut milk to obtain Sumbawa oil for traditional medicine. Coconut milk is a colloidal system of stable oil in water (O/W) microemulsion. Within a particular time, the emulsion will split to produce oil (VCO), protein, and water due to the colloid equilibrium on the stability of the coconut milk emulsion. The purpose of this study was to compare the microemulsion stability of the coconut milk colloid system. The VCO was isolated by heating, enzymatically, acidifying, and adding whiting methods for comparison. The physical stability of the O/W microemulsion was measured by the volume of VCO produced from various isolation methods in simple laboratory experiments. The results showed that the physical stability of the O/W microemulsion on VCO isolation by enzymatic method using papain enzyme was the least.

Interplay between slow interfacial water diffusion and colloid dynamics: A way to probe colloidal transitions.

2003 ◽  
Vol 790 ◽  
Author(s):  
P.E. Levitz
Keyword(s):  
Fluid Dynamics ◽  
Phase Transition ◽  
Particle Surface ◽  
Low Frequency ◽  
Colloidal Suspensions ◽  
Molecular Structures ◽  
Lyotropic Liquid Crystals ◽  
Water Dynamics ◽  
Colloidal System ◽  
Confined Water

ABSTRACTParticle fluctuations in colloidal suspensions are generally considered to be much slower than the embedded fluid dynamics. It was recently proposed that the fluid self-diffusion nearby an interface follows Lévy statistics, extending the time domain of the fluid dynamics towards the low frequency range. It is then possible to probe colloidal particle motion and especially its evolution during a phase transition looking at the slow dynamics of the fluid molecule close to an particle surface. Using field cycling NMR relaxometry, we show how the slow and confined water dynamics at proximity of a colloidal surface provide an original way to follow the glass transition of a colloidal system made of plate-like Laponite particles, a synthetic clay. The interplay between fluid Levy dynamics and particle jamming is discussed. An analytical model involving correlated elementary water time steps on the colloidal interface is proposed and critically compared to our experimental data. The method permits probing of colloidal motions and especially their evolution during a phase transition in a new way. This method can be extended to other systems including mineral lyotropic liquid crystals and biological molecular structures.

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