Effect Of Stabilizer Concentration Research Articles

Formulation and Process Optimization of Rauvolfia serpentina Nanosuspension by HPMC and In Vitro Evaluation of ACE Inhibitory Potential.

Angiotensin converting enzyme (ACE) overactivation is one of the primary causes of hypertension, which leads to cardiovascular disorders all over the world. In the scientific world, nanosuspension is a novel area of study that could offer an alternative treatment for active pharmaceuticals that are not well soluble in water. Since active compounds' bioavailability is reduced by their poor solubility, there are eventually fewer applications. Drug solubility, dissolving rate, and bioavailability are improved by nanosuspension, which shrinks medication particle size into the nanoscale range and boosts the surface area to volume ratio of the drug. There is a need to prepare Rauvolfia serpentina's nanosuspension in order to get around some of the major challenges that it faces because of its poor solubility and wide range of biological activities. Using the antisolvent precipitation approach, a nanosuspension of Rauvolfia serpentina was created with hydroxy propyl methyl cellulose (HPMC). Rouvolfia serpentina nanosuspensions were prepared using a design of expert (DOE) approach, which allowed for the evaluation of key process parameters. To get an optimal sample, the effects of stabilizer concentration and anti-solvent volume on particle size, zeta potential, and PdI using CCD-RSM were investigated. Using the substrate Hippuryl-histidyl-leucine, the in vitro ACE inhibitory potential was assessed. On human erythrocytes, the safety of nanosuspension was evaluated in vitro. The ideal value of independent variables was discovered to be 0.25% w/v in order to achieve the desired response. Using scanning electron microscopy, the morphology of optimized nanosuspension was discovered to be rod-shaped (SEM). Compared to nanoformulation, crude extract had higher ACE inhibitory potential (83.11%). Human erythrocytes were found to be unaffected by nano-sized particles.

Nanosuspension coated multiparticulates for controlled delivery of albendazole

Objective Improving solubility and bioavailability of albendazole (ALB). Significance ALB is a broad-spectrum anthelminthic BCS class II drug with aqueous solubility of solubility of 4.1 mg/l at 25 °C and oral bioavailability of <5%. Methods ALB nanosuspensions (NSs) were prepared by evaporative antisolvent precipitation using tocopherol polyethylene glycol succinate (TPGS) and polyvinyl pyrrolidone (PVP) as stabilizers and characterized for particle size, polydispersity index, and zeta potential. 32 factorial design was used to investigate effect of stabilizer concentration and speed of stirring on particle size. Concentration of TPGS was varied from 0.03 to 0.05% w/v and PVP K-30 was constant at 0.04% w/v. Stirring speed range was 1000–3000 rpm. Optimized NS was loaded on Espheres and coated with Eudragit S10& L100 and studied for friability, surface morphology and release kinetics. Results Factorial experiments revealed pronounced effect of TPGS on particle size. Optimized batch had particle size of 251 ± 7.2 nm and zeta potential −16.2 ± 2.68 mV. Saturation solubility showed increase of 16-fold in water whereas in phosphate buffer increase was fourfold. ALB-NS secondary coated Espheres released 94.3% drug in 10 h whereas ALB-MS (microsuspension) coated Espheres showed 58% release. A 1.3-fold increase in AUC0-10h was evident. Permeation from ALB-NS coated Espheres was 32% in 60 min while for ALB-MS coated Espheres it was 20%. Permeation increase occurred due to presence of TPGS which acts as a permeation enhancer.

Effect of stabilizer concentration on the size of silver nanoparticles synthesized through chemical route

In this study, we address the effect of concentration of the stabilizing agent, viz. trisodium citrate for tailoring the particle size and size distribution of silver nanoparticles produced via wet chemical method. The synthesized silver nanoparticles have been characterized by different structural and compositional characterization tools. The concentration of the stabilizing agent has been varied in different experimental runs and optimized to get stable particles with a mean size of 7 nm and a narrow size distribution.

Experimental investigation on the spread of aqueous foam over ethanol surface

Abstract The presence of ethanol has an adverse effect on foam spreading, and ethanol fire is difficult to extinguish with aqueous fire-fighting foams. Thus, it is necessary to explore the foam formulation suitable for ethanol fuels and study the spreading behavior of foam over ethanol surface. In the current work, stable foams based on hydrocarbon surfactant (SDS), fluorocarbon surfactant (FC1157), and polymers (XG) were prepared by using the compressed-air foam system. The spreading behaviors of foam on polar ethanol and non-polar heptane surface were observed and compared. Furthermore, the effects of stabilizer concentrations, foam flow rates and expansion ratios on foam spreading performance were investigated, respectively. The results indicate that aqueous SDS foam can spread on the heptane layer continuously, but it is difficult to cover the ethanol surface. The addition of XG and FC1157 can synergistically improve the spreading performance of aqueous foam over ethanol. Depending on stabilizer concentrations, there are remarkable differences in foam spreading behaviors. Besides, different foam application parameters including expansion ratios and foam flow rates significantly affect the foam spreading rate, despite the same foam formulation. The research methods and results guide the optimal design of foam formulations as well as the practical application of aqueous foam for ethanol fire extinguishment.

Effect of stabilizer concentration on the cavitation erosion resistance characteristics of the electroless nickel plated gray cast iron in seawater

In this study, electroless nickel (EN) plating was performed with stabilizer concentration to improve cavitation erosion resistance of gray cast iron under marine environment. Cavitation erosion tests were carried out in natural seawater solution in accordance with modified ASTM G32. The change of stabilizer concentration affected the plating rate, P content, and average crystal size of EN coating. The decrease of the plating rate with the stabilizer concentration and the flake-shaped graphite exposed to the gray cast iron surface negatively affected the cavitation erosion and corrosion prevention. In particular, cavitation erosion damage of EN coating was accelerated due to combined galvanic corrosion when the EN coating was destroyed and the substrate was exposed under the cavitation erosion environment.

Effect of surfactants and gelatin on the stability, rheology, and encapsulation efficiency of W1/O/W2 multiple emulsions containing avocado oil

AbstractThe main aim of this study was to determine the effect of emulsifiers on the stability, rheology. and encapsulation efficiency of W1/O/W2 multiple emulsions, which contain avocado oil and NaCl encapsulated. The primary emulsion contained 5 or 6 wt % polyglycerol polyricinoleate (PGPR) and 3 or 4 wt % gelatin, and the secondary emulsion contained 2 wt % Tween 40 or Tween 80. Each of the emulsions prepared presented non‐Newtonian shear thinning and concentrate solution behavior at 25 °C. Emulsions containing Tween 40 had a higher stability than those containing Tween 80. The best encapsulation efficiency was obtained for the emulsion containing 6 wt % PGPR, 3 wt % gelatin, and 2 wt % of Tween 40, which retained 92% of NaCl in the inner aqueous phase after 20 days of storage at 4 °C. Therefore, the use of Tween 40 combined with PGPR and gelatin has great potential to form stable multiple emulsions. Furthermore, emulsions combined with avocado oil can be associated with health benefits.Practical applicationsThis article presents a study on the effects of stabilizer concentrations on some properties of multiple emulsions prepared with avocado oil. Tween 40 was used as secondary emulsifier and was found to be a good alternative to Tween 80, one of the most commonly used emulsifiers in the food industry. Besides that, avocado oil has a great potential as food ingredient, due to its health benefits, but is scarcely used and studied. The characterization of multiple emulsions is presented along with a proposal of using them in the production of several food products.

Preparation and Evaluation of Ketoprofen Nanosuspension Using Solvent Evaporation Technique

The effective surface area of drug particle is increased by a reduction in the particle size. Since dissolution takes place at the surface of the solute, the larger the surface area, the further rapid is the rate of drug dissolution. Ketoprofen is class II type drug according to (Biopharmaceutics Classification System BCS) with low solubility and high permeability. The aim of this investigation was to increase the solubility and hence the dissolution rate by the preparation of ketoprofen nanosuspension using solvent evaporation method. Materials like PVP K30, poloxamer 188, HPMC E5, HPMC E15, HPMC E50, Tween 80 were used as stabilizers in perpetration of different formulas of Ketoprofen nanosuspensions. These formulas were evaluated for particle size, entrapment efficiency of drug (EE), effect of stabilizer type, effect of stabilizer concentration and in-vitro dissolution studies. All of the prepared Ketoprofen nanosuspensions formulas showed a particle size result within Nano range. The average particle size of Ketoprofen nanosuspensions formulas was observed from 9.4 nm to 997 nm. Entrapment efficiency was ranged from 79.23% to 95.41 %. The in vitro dissolution studies showed a significant (p<0.01) enhancement in dissolution rate of nanosuspension formulas compared to pure drug (drug alone) and physical mixture (drug and stabilizer). The results indicate the suitability of solvent evaporation method for Ketoprofen with improved in vitro dissolution rate and thus perhaps enhance fast onset of action for drug.

Preparation and Evaluation of Ketoprofen Nanosuspension Using Solvent Evaporation Technique

&#x0D; &#x0D; The effective surface area of drug particle is increased by a reduction in the particle size. Since dissolution takes place at the surface of the solute, the larger the surface area, the further rapid is the rate of drug dissolution. Ketoprofen is class II type drug according to (Biopharmaceutics Classification System BCS) with low solubility and high permeability. The aim of this investigation was to increase the solubility and hence the dissolution rate by the preparation of ketoprofen nanosuspension using solvent evaporation method. Materials like PVP K30, poloxamer 188, HPMC E5, HPMC E15, HPMC E50, Tween 80 were used as stabilizers in perpetration of different formulas of Ketoprofen nanosuspensions. These formulas were evaluated for particle size, entrapment efficiency of drug (EE), effect of stabilizer type, effect of stabilizer concentration and in-vitro dissolution studies. All of the prepared Ketoprofen nanosuspensions formulas showed a particle size result within Nano range. The average particle size of Ketoprofen nanosuspensions formulas was observed from 9.4 nm to 997 nm. Entrapment efficiency was ranged from 79.23% to 95.41 %. The in vitro dissolution studies showed a significant (p&lt;0.01) enhancement in dissolution rate of nanosuspension formulas compared to pure drug (drug alone) and physical mixture (drug and stabilizer). The results indicate the suitability of solvent evaporation method for Ketoprofen with improved in vitro dissolution rate and thus perhaps enhance fast onset of action for drug.

Investigation of effect of electric field on silver nanoparticles in order to separation of them from aqueous medium using electrocoagulation process

Abstract The behavior of silver nanoparticles (AgNPs) under an applied electric field depends primarily on their stabilizing agent. This research aimed at investigating the behavior of AgNPs and their stabilizers under the electrocoagulation (EC) process. In two separate experiments, sodium citrate and polyvinylpyrrolidone (PVP) were used as the nanoparticles’ stabilizers. Stability of the particles was studied while applying an electrical current with various voltages. Efficiency of the EC process was investigated for these different AgNPs sols. In the case of sodium citrate for various voltages, the plasmon resonance peak of the sample was disappeared after applying the electric field for 90 min, reflecting the removal of AgNPs in the sol by 99.91%. In the case of PVP for various voltages of the EC process for 10 min, the absorbance peak disappeared, and removal efficiency of AgNPs reached 99.98%. Effect of stabilizer concentration on the EC process was investigated. As sodium citrate concentration increased, the stability of AgNPs under an equall applied electric field increased, while the increase of the PVP concentration did not influence on the stability of AgNPs. Kinetic of AgNPs removal was also studied.

グルコース燃料電池のためのAu-Ptアノード触媒の電気化学特性に及ぼす安定剤濃度の効果

グルコース燃料電池のためのAu-Ptアノード触媒の電気化学特性に及ぼす安定剤濃度の効果

Structural and optical properties of ZnO thin films deposited by sol–gel method: effect of stabilizer concentration

Nanocrystalline thin films of ZnO were successfully deposited on Si substrate via sol–gel method using zinc acetate dehydrate as a precursor and 2-methoxy ethanol as a solvent. The effect of stabilizer concentration on the structural and optical properties of the ZnO thin film was investigated as the stabilizer concentration affects the growth orientation of ZnO thin films prepared by sol–gel method. The growth in (002) plane of hexagonal structure is preferred in many applications as the 2-dimensional Zn atoms population is highest in this orientation. The growth of (002)-oriented ZnO films was optimized with the concentration of the stabilizer (triethanolamine). The crystal structures of the samples were analyzed using X-ray diffractometer confirming the polycrystalline nature and hexagonal structure of films. In order to estimate the preferential crystallite orientation quantitatively, the texture coefficient (Tc) was calculated. The particle size and strain was also found to change with concentration of stabilizer. SEM results confirm the formation of nanocrystalline thin films with homogeneous morphology. Photoluminescence characteristics show a direct band gap transition which shifts towards lower wavelength with increase in stabilizer concentration. It was observed that the stabilizer concentration is the most important factor to grow a highly (002)-oriented ZnO film along c-axis.

Effect of formulation variables on preparation of celecoxib loaded polylactide-co-glycolide nanoparticles.

Polymer based nanoparticle formulations have been shown to increase drug bioavailability and/or reduce drug adverse effects. Nonsteroidal anti-inflammatory drugs (e.g. celecoxib) reduce prostaglandin synthesis and cause side effects such as gastrointestinal and renal complications. The aim of this study was to formulate celecoxib entrapped poly lactide-co-glycolide based nanoparticles through a solvent evaporation process using didodecyldimethylammonium bromide or poly vinyl alcohol as stabilizer. Nanoparticles were characterized for zeta potential, particle size, entrapment efficiency, and morphology. Effects of stabilizer concentration (0.1, 0.25, 0.5, and 1% w/v), drug amount (5, 10, 15, and 20 mg), and emulsifier (lecithin) on nanoparticle characterization were examined for formula optimization. The use of 0.1, 0.25, and 0.5% w/v didodecyldimethylammonium bromide resulted in a more than 5-fold increase in zeta potential and a more than 1.5-fold increase in entrapment efficiency with a reduction in particle size over 35%, when compared to stabilizer free formulation. Nanoparticle formulations were also highly influenced by emulsifier and drug amount. Using 0.25% w/v didodecyldimethylammonium bromide NP formulations, peak zeta potential was achieved using 15 mg celecoxib with emulsifier (17.15±0.36 mV) and 20 mg celecoxib without emulsifier (25.00±0.18 mV). Peak NP size reduction and entrapment efficiency was achieved using 5 mg celecoxib formulations with (70.87±1.24 nm and 95.55±0.66%, respectively) and without (92.97±0.51 nm and 95.93±0.27%, respectively) emulsifier. In conclusion, formulations using 5 mg celecoxib with 0.25% w/v didodecyldimethylammonium bromide concentrations produced nanoparticles exhibiting enhanced size reduction and entrapment efficiency. Furthermore, emulsifier free formulations demonstrated improved zeta potential when compared to formulations containing emulsifier (p<0.01). Therefore, our results suggest the use of emulsifier free 5 mg celecoxib drug formulations containing 0.25% w/v didodecyldimethylammonium bromide for production of polymeric NPs that demonstrate enhanced zeta potential, small particle size, and high entrapment efficiency.

Towards conducting inks: Polypyrrole–silver colloids

The oxidation of pyrrole with silver nitrate in the presence of suitable water-soluble polymers yields composite polypyrrole–silver colloids. The polypyrrole–silver nanoparticles stabilized with poly(N-vinylpyrrolidone) have a typical size around 350nm and polydispersity index 0.20, i.e. a moderate polydispersity in size. Similar results have been obtained with poly(vinyl alcohol) as stabilizer. The effect of stabilizer concentration on the particle size is marginal. In the present study, several types of stabilizers have been tested in addition to currently used poly(N-vinylpyrrolidone). Transmission electron microscopy and optical microscopy revealed the gemini morphology of polypyrrole and silver colloidal nanoparticles and confirmed their size and size-distribution determined by dynamic light scattering. The use of colloidal dispersions provides an efficient tool for the UV–vis and FT Raman spectroscopic characterization of polypyrrole, including the transition between polypyrrole salt and corresponding polypyrrole base. The dispersions were used for the preparation of coatings on polyethylene terephthalate foils, and the properties for polypyrrole–silver composites have been compared with those produced from polypyrrole colloids alone.

Formulation, characterization and optimization of Hepatitis B surface antigen (HBsAg)-loaded chitosan microspheres for oral delivery

Context: Approximately 400 million persons worldwide have chronic hepatitis B. This is due to problems associated with vaccine delivery, stability and cost. Hence the present challenge in vaccinology is to develop safer, cheaper and easy-to-deliver forms of vaccines. A novel needle-free oral vaccine will be an ideal tool to fight this silent killer disease.Objective: The aim of this work was to prepare and evaluate chitosan-loaded HBsAg microspheres for oral delivery.Materials and methods: Chitosan microspheres were prepared by emulsion solvent evaporation technique. To overcome the enzymatic and permeation barrier, protease inhibitors and permeation enhancers were also added. Studies were conducted to find the effect of stabilizer concentration, stirring speed, cross-linking agent and polymer concentration on microsphere size and entrapment efficiency. Formulations were characterized for their particle size, entrapment efficiency. They were also evaluated for the in vitro drug release, in vivo performances and the effect of different storage conditions.Results: HBsAg-loaded chitosan microspheres with bacitracin as protease inhibitor showed better protective levels of immunity after oral administration comparing with aprotinin as protease inhibitor. Stability at room temperature up to a period of four months reduces incomplete vaccine coverage and logistic requirements.Conclusion: The study signifies the potential of the formulated chitosan microspheres for effective oral administration of HBsAg.

Effect of Stabilizer Concentration, Pressure and Temperature on Polymerization Rate and Molecular Weight Development in RAFT Polymerization of MMA in scCO2

AbstractSummary: An experimental study on the effect of stabilizer concentration, pressure (100 to 500 bar), and temperature (65 to 85 °C) on polymerization rate and molecular weight development in the reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) in supercritical carbon dioxide (scCO2) is presented. AIBN was used as initiator, S‐Thiobenzoyl thioglycolic acid as RAFT agent, and Krytox® 257 FSL as stabilizer. It was observed that the polymerization proceeded in a controlled manner. High conversions can be reached in reasonable times. Fairly low polydispersities (around 1.2) are possible if either pressure or temperature are increased, but better results are obtained if the polymerization proceeds at the upper temperature value of 85 °C.

Effect of stabilizer concentration and controller structure and composition on polymerization rate and molecular weight development in RAFT polymerization of styrene in supercritical carbon dioxide

An experimental study on the reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene in supercritical carbon dioxide is presented. A 38 mL, high-pressure view cell with two frontal and two lateral sapphire windows was used as reactor. Poly(styrene-block-dimethylsiloxane) was used as stabilizer. The performance as RAFT controllers of S-thiobenzoyl thioglycolic acid, methyl naphthalene dithiobenzoate, 4-methyl allyl dithiobenzoate, and benzyl-N,N-dimethyldithiocarbamate was compared. The effect of stabilizer concentration and controller structure and concentration on polymerization rate and molecular weight development was analyzed. Good performance was obtained with the first three controllers, although simultaneous high polymerization rates and low polydispersities were not possible with either of them. The performance of the fourth RAFT controller was poor.

Dispersion polymerization of methyl methacrylate: Effect of stabilizer concentration

AbstractIn dispersion polymerizations of methyl methacrylate (MMA), little difference was found in the polymerization kinetics with varying stabilizer (PVP K‐30) concentration, indicating that in contrast to emulsion polymerization, the kinetics of these dispersion polymerizations are independent of the number of particles. Comparing MMA precipitation and dispersion polymerizations revealed that nuclei formation in the latter results from precipitation polymerization occurring in the continuous phase, which can contribute significantly to the kinetics, and especially to the molecular weight distributions. No change was found in the molecular weight distribution of the PVP during a dispersion polymerization, nor was there any measurable difference between using fresh and recycled stabilizer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Computer modelling of ion migration in zirconia

Defect structure and migration pathways of cations in cubic zirconia (ZrO2) have been calculated using two computer modelling techniques. The first is based on the Mott–Littleton method, which considers defects to be embedded in an otherwise perfect crystal, and the second is the supercell approach, which allows finite defect concentrations to be modelled. Using the first approach, migration pathways for both intrinsic and dopant cations have been calculated. Activation energies ranging from 3.1 to 5.8 eV have been calculated assuming a vacancy mechanism. For highly charged dopants a curved pathway was found to be favoured over a straight pathway. The effect of stabilizer concentration on the properties of the system investigated has been analysed using the supercell method; 3 × 3 × 3 and 4 × 4 × 4 supercells containing 3–40 mol% calcia (CaO) or yttria (Y2O3) have been constructed assuming a random distribution of both dopant cations and oxygen vacancies. After relaxation the oxygen vacancies were found to be located adjacent to the zirconium cations in the CaO-doped system, while remaining randomly ordered in the Y2O3-doped system. Also cation vacancies were created, and after relaxation they were surrounded in all systems (CaO-stabilized ZrO2 and Y2O3-stabilized ZrO2) on average by 2.7 oxygen vacancies.

A Theoretical Model for the Diffusion-Limited Thermal Oxidation of Elastomers at Medium Temperatures

Abstract A theoretical model is presented to describe the diffusion-limited thermal oxidation of stabilized elastomers, with no assumptions concerning the concentration of oxygen, the kinetic chain length, the ratio of termination rate constants, or the existence of a steady state for oxidation products. Model predictions are found to agree qualitatively with reported main features of elastomer thermal oxidation. The model is used to simulate the thermal ageing of thick natural rubber slabs under ambient air at 80–150 °C. Among others, the effect of stabilizer concentration and thickness of the aged parts on the evolution of the oxidation process is discussed. Conditions are also identified under which the oxidation process may be considered free of oxygen mass transfer limitations.

The effect of stabilizer concentration on the air-plasma-induced surface oxidation of crosslinked polydimethylsiloxane

The concentrations of three stabilizers—a hindered phenol (Irganox 1076), a hindered amine light stabilizer (Tinuvin 770) and a bifunctional stabilizer with chain-breaking hindered phenol and secondary amine and hydroperoxide-decomposing sulphide moieties (Irganox 565)—in crosslinked polydimethylsiloxane were varied using swelling solutions of the stabilizers at different concentrations. The concentration of the stabilizer in the rubber was assessed by UV-Vis spectroscopy of Soxhlet and microwave assisted extracts. Irganox 1076 and Tinuvin 770 were soluble in polydimethylsiloxane to at least 0.2–0.3 wt.%, whereas the solubility of Irganox 565 was considerably lower. The samples were exposed to GHz air plasma and the surface structures of the exposed samples were studied by X-ray photoelectron spectroscopy, and by optical and scanning electron microscopy after uniaxial stretching. The plasma exposure time required for the formation of an oxidised glassy layer increased in a linear fashion with increasing stabilizer concentration, suggesting that the consumption rate was constant in time during the plasma exposure. Tinuvin 770 showed the strongest overall protecting effect whereas Irganox 565 showed the strongest protecting effect per mass fraction of stabilizer. Irganox 1076 was of moderate efficiency. The results suggest that efficient protection towards air plasma is achieved with hindered amine stabilizers or with stabilizers combining chain-breaking and hydroperoxide-decomposing functions. Differential scanning calorimetry showed that Tinuvin 770 and Irganox 565 protected polydimethylsiloxane against thermal oxidation at elevated temperatures. The chemical consumption of these stabilizers followed basically the classical scheme with zero-order kinetics and a rate constant obeying the Arrhenius law.