Effect Of Various Stabilizers Research Articles

Effect of a stabilizer on the structure, synthesis, and tribological properties of silver nanoparticles

The structure and properties of nanoparticles are greatly influenced by the synthesis method and the stabilizer used in their preparation. The paper presents the results of the effect of various stabilizers (gelatin, sodium citrate, sodium borohydride) on the structure, synthesis, and tribotechnical properties of silver nanoparticles. The mechanism of the formation and growth of silver nanoclusters was investigated using quantum-chemical calculations with full optimization of all parameters using the density functional theory (DFT) PBEPBE/Lanl2DZ method. It is shown that the use of organic stabilizers (for example, gelatin) leads to an increase in the stability of stabilized silver clusters. Such systems have greater conformational flexibility and a large number of molecular donor oxygen centres in their composition. The effect of the stabilizer on the structure of the Ag13 silver cluster was revealed in four model systems: gelatin, ammonium chloride NH4Cl, sodium borohydride NaBH4, and trisodium citrate Na3C6H5O (Na3Cit). Silver nanoparticles (AgNPs) obtained by the sonoelectrochemical, citrate, borohydride, and citrate-borohydride method varied in size from nanometers to several tens of nanometers. As a result of tribotechnical tests of lubricants with the obtained silver nanoparticles, a positive effect of stabilized silver clusters was revealed in the composition of lubricant compositions. The best tribotechnical characteristics were shown by lubricating compositions containing AgNPs stabilized with gelatin. It was found that a decrease in the size of gelatin stabilized AgNPs, when added to lubricants, leads to an increase in the tribological properties.

Biodegradable Polymers-Based Smart Nanocrystals for Loxoprofen Delivery with Enhanced Solubility: Design, Fabrication and Physical Characterizations.

Nanocrystals are carrier-free, submicron-sized, colloidal drug delivery systems with particle sizes in the mean nanometer range. Nanocrystals have high bioavailability and fast absorption because of their high dissolution velocity and enhanced adhesiveness to cell membranes. Loxoprofen, a nonsteroidal anti-inflammatory drug belonging to the Biopharmaceutical Classification System (BCS) II drug class, was selected as the model drug. The aim of this study was to formulate nanocrystals of loxoprofen. A total of 12 formulations (F1 to F12) were prepared. An antisolvent technique was used to determine the effects of various stabilizers and processing conditions on the optimization of formulations. The various stabilizers used were hydroxypropyl methylcellulose (0.5%), polyvinylpyrrolidone (0.5%), and sodium lauryl sulfate (0.1%). The various characterizations conducted for this research included stability studies at 25 °C and 4 °C, scanning electron microscopy, transmission electron microscopy (TEM), X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), zeta potentials, polydispersity indexes, and dissolution studies. F10 was the optimized formulation that showed stability at room temperature, as well as at a refrigerated temperature, for 30 days. A high dissolution rate (100% within the first 10 min) was shown by comparative dissolution studies of nano-suspensions with the micro-suspension and raw loxoprofen. F10 formulation had a non-porous and crystalline morphology on evaluation by TEM and XRPD, respectively, and the average particle size was 300 ± 0.3 nm as confirmed by TEM. DSC recorded a reduction in the melting point (180 °C processed and 200 °C unprocessed melting points). The dissolution rate and solubility of the formulated loxoprofen nanocrystals were significantly enhanced. It can be concluded that selecting suitable stabilizers (i.e., polymers and surfactants) can produce stable nanocrystals, and this can potentially lead to a scaling up of the process for commercialization.

A rapid method for approximative evaluation of thermooxidative stability of organic materials.

In this work, a novel procedure for fast assessment of the material residual stability is proposed. The method resides in integral isoconversional kinetic analysis of the thermal oxidation of unaged material employing the Berthelot–Hood temperature function. Subsequently, the obtained conversion-independent kinetic parameter D is also employed for samples aged in various regimes. The value of conversion-dependent parameter A for aged samples is calculated from the oxidation onset temperature measured at 5 °C min−1. The residual stabilities are then calculated as a simple ratio of the parameter A of aged material to that of the unaged one. The method has been applied and verified for the samples of low-density polyethylene aged by thermal, radiation and combined ageing. The method can also be employed for high-throughput screening of the effect of various stabilizers and antioxidants in a given organic matrix.

Effect of various stabilizers on the stability of lansoprazole nanosuspension prepared using high shear homogenization: Preliminary investigation

The purpose of the current research work was to prepare a nanosuspension of the model drug lansoprazole (LSP) and investigate the effect of various stabilizers on the stability of the nanosuspension prepared using the high shear homogenization technique. In this study, polymeric stabilizers like polyvinylpyrrolidone K-30, polyvinylpyrrolidone K-90, polyvinyl alcohol, sodium alginate, and hydroxypropyl methylcellulose E15 and surfactants like sodium lauryl sulfate and Tween 80 were explored. The prepared nanosuspensions were evaluated for particle size distribution (PSD), polydispersity index (PI), zeta potential, and drug loading. Saturation solubility and in-vitro dissolution studies of optimized nanosuspension and coarse LSP powder were also carried out to determine the extent of solubility enhancement. PSD and zeta potential revealed that all the stabilizers when used alone could not significantly reduce the particle size and stabilize the colloidal dispersion. However, a combination of polymeric stabilizer and surfactant showed significant particle size reduction with an average particle size of 428.5 nm, PI 0.363, and a stable zeta potential value of −25.8 mV. Therefore, it can be concluded that LSP nanosuspension prepared by the high shear homogenization technique can be effectively stabilized by a combination of stabilizers.

Solvothermal Synthesis of YF<sub>3</sub>:Ce<sup>3+</sup> Nanophosphors for Medical Applications

In this paper, the time effect of hydrothermal synthesis on YF3 morphology particles is considered. The work was carried out on X-ray-excited YF3:Ce3+ phosphors. The synthesis was carried out by the hydrothermal method, since it avoids high temperatures leading to particle agglomeration. The first stage of research consisted in identifying the most favorable medium for obtaining the required phase and size - water or organic matter (ethylene glycol and ethanol). Research has shown that ethylene glycol has all the advantages: it prevents agglomeration, allows us to get the required phase. Hydrothermal synthesis of YF3 samples to determine the optimal synthesis time was carried out according to the same scheme - in an organic medium of ethylene glycol without using stabilizers for 4, 8, 12, 16, 20 hours. Our study showed that it is possible to obtain a YF3 sample that meets the necessary requirements (including nanoscale) within 16 hours, moreover, without the use of stabilizers. In parallel with the study of the synthesis duration, an experiment was carried out on the effect of various stabilizers on the properties of the YF3:Ce3+ phosphors (5%). The synthesized nanophosphors possessed effective X-ray luminescence with a maximum in the region of 300 nm, which makes it possible to use them in the composition of preparations for PDT.

Synthesis and Luminescent Properties of Perovskite Quantum Dots

In this paper, we obtained nanoparticles based on ABX3 type of metal halide perovskites using the growth method of colloidal quantum dots in non-polar environment. The development of technological processes allowed us to synthesize the studied nanoparticles with room temperatures. The dependence of the photoluminescence intensity of the concentration of sols dots was determined using the photoluminescence method in the range from 400 to 700 nm. The effect of various stabilizers on the optical properties of nanoparticles was studied and the optimal composition of the stabilizer was defined. The method of dynamic light scattering was used to estimate the approximate dimensions of the synthesized ABX3 type of metal halide nanoparticles.

Effect of Stabilizers on Encapsulation Efficiency and Release Behavior of Exenatide-Loaded PLGA Microsphere Prepared by the W/O/W Solvent Evaporation Method.

The aim of this study was to investigate the effects of various stabilizers on the encapsulation efficiency and release of exenatide-loaded PLGA (poly(lactic-co-glycolic acid)) microspheres prepared by the water-in-oil-in-water (W/O/W) solvent evaporation (SE) method. It was shown that the stabilizers affected exenatide stability in aqueous solutions, at water/dichloromethane interfaces, on PLGA surfaces, or during freeze-thawing and freeze-drying procedures. Sucrose predominantly reduces instability generated during freeze-thawing and freeze-drying. Phenylalanine prevents the destabilization at the water–dichloromethane (DCM) interface through decreased adsorption. Poloxamer 188 enhances stability in aqueous solutions and prevents adsorption to PLGA. Proline and lysine decrease adsorption on PLGA surfaces. Fourier transform infra-red spectroscopy (FT-IR) was used to find the molecular interaction of additives with exenatide or PLGA. Additives used in stability assessments were then added stepwise into the inner or outer water phase of the W/O/W double emulsion, and exenatide-loaded microspheres were prepared using the solvent evaporation method. The effect of each stabilizer on the encapsulation efficiency and release behavior of microspheres correlated well with the stability assessment results, except for the negative effect of poloxamer 188. Particle size analysis using laser diffractometry, scanning electron microscopy (SEM), water vapor sorption analysis, differential scanning calorimetry (DSC), and circular dichroism (CD) spectroscopy were also employed to characterize the prepared exenatide-loaded PLGA microsphere. This study demonstrated that an adequate formulation can be obtained by the study about the effect of stabilizers on peptide stability at the preformulation step. In addition, it can help to overcome various problems that can cause the destabilization of a peptide during the microsphere-manufacturing process and sustained drug release.

The Effect of Various Stabilizers on Preserving Immunogenicity of Lyophilized Mumps Vaccines.

Chemical stabilizers are added to live attenuated vaccines for enhancing the virus stability. The aim of this study was to evaluate the effect of various stabilizers on preserving immunogenicity of lyophilized mumps vaccines. An experimental study. Three mumps vaccines with different formulations were inoculated to three groups of Guinea pigs. Sterile water was injected to eight Guinea pigs as a control group. Blood samples were collected before inoculation and on 14, 28 and 42 d after vaccine injection. Mumps antibodies in the sera were measured using hemagglutination inhibition assay (HAI). All three formulated mumps vaccines induced antibody in Guinea pigs after two weeks. Formulation 1 containing trehalose dihydrate and formulation 2 comprised human serum albumin stimulated antibodies in the higher level than Razi routine formulation. Various stabilizers have different preservation potencies that differently affect immune response against virus. More stable and more immunogenic vaccines can be produced using stabilizers containing trehalose dihydrate.

Enhanced Solubility and Dissolution Rate of Clopidogrel by Nanosuspension: Formulation via High Pressure Homogenization Technique and Optimization Using Box Behnken Design Response Surface Methodology

Effect of various stabilizers on the stability of lansoprazole nanosuspension prepared using high shear homogenization: Preliminary investigationShobha Ubgade, Aditi Bapat, Vaishali Kilor

Effects of Various Stabilizers on Sensorial Quality of Yoghurt

This research was aimed to preserve the yoghurts using stabilizers without refrigeration in terms of syneresis and sensory analysis. Yoghurts were prepared using three stabilizers viz., gelatin, carboxymethylcellulose and sodium alginate and a control (without stabilizer). For which set type yoghurt was prepared with 2% starter culture inoculation and was incubated at 43⁰C for 3 hours and was stored at 5-7⁰C. Statistical analysis of all the treatments showed that 0.2 % stabilizer containing samples were significantly superior (p<0.05). The best samples with stabilizers containing 0.2% were again compared with control. From this, 0.2% gelatin added sample had significantly superior (p<0.05) scores. Shelf life of the sample was observed and it was compared with control at refrigerated condition. Sensorial gelatin added sample was best up to eleventh days while the control was best up to seventh days. Gelatin added sample showed less syneresis compared to control and adding stabilizer seems slower the acid development and syneresis of yoghurt in terms of storage time.Sunsari Technical College Journal 2015,2(1):7-12

Application of Real-Time PCR method for evaluation of measles vaccine heat stability

The Plaque Forming Unit (PFU) and Tissue Culture Infectious Dose50 (TCID 50 ) methods are used for evaluation of vaccine heat stability and effect of various stabilizers on thermal stability of vaccines. The aim of present study is using Real-Time PCRtechniquefor estimation of vaccine degradation rate and thermal stability of measles vaccines. Lyophilized measles vaccines containing three various stabilizers were reconstituted with distilled water. Three vial of each vaccine incubated at25˚C for 0, 4 and 8 hours. Titer of virus in vaccines calculated by TCID 50 method. Also after RNA Extraction and cDNA synthesis, the RNA copy numbers of viruses in vaccines were estimated by absolute quantitative Real-Time PCRtesting. The data were analyzedby SPSS 19 and Sigma Plot 11 software.The result of this study showed there is a significant relationshipbetween vaccine degradation rate calculated with TCID 50 and Real-Time PCR method (p<0.05). ThereforeReal-Time PCR is a good complement or appropriate replacement to traditional methods.Titration methods based on cell culture are gold tests for titration of viral vaccines and estimation of heat stability but Real-Time PCR technique can also be used for this goals. This method is faster, cheaper and easier than TCID 50 .

Inhalation of alendronate nanoparticles as dry powder inhaler for the treatment of osteoporosis

The precipitation technique was used to prepare non-polymeric alendronate nanoparticles. The influence of various formulation parameters on the average particle size was investigated and the effect of various stabilizers (PVA, tween, chitosan, alginate, PEG, HPMC, poloxomers) was evaluated. The selection of surfactant was a key factor to produce particles with desired properties. Poloxomer F68 was found best in achieving the minimum particle size and providing physical stability to the drug. On basis of preliminary trials, a central composite design was employed to study the effect of independent variables, drug concentration (X1), antisolvent volume (X2), stirring speed (X3), and stabilizer concentration (X4) on the average particle size. The drug and stabilizer concentrations exhibited a more significant effect on a dependent variable. The particle size varied from 62 to 803.3 nm depending upon the significant terms. The validation of optimization study, performed using six confirmatory runs, indicated very high degree of prognostic ability of response surface methodology, with mean percentage error (±SD) as −2.32 ± 2.47. The minimum particle size (44.11 nm) was predicted at 10 mg/ml drug concentration, 20 ml antisolvent volume, 925 rpm stirring speed, and 8.5% stabilizer concentration with 98.16% experimental validity. Respirable fraction for optimized nanosized alendronate (43.85% ± 0.52%) was significantly higher when compared with commercial alendronate (17.6 ± 0.32). Mass median aerodynamic diameter of designed particles was 3.45 µm with geometric standard deviation of 2.10.

Development and Evaluation of Novel Polymeric Nanoparticles of Brimonidine Tartrate

Micro and nanoparticulate carriers have been in focus in ophthalmic drug delivery with the objective of improving bioavailability, drug targeting and reducing pulse entry of the drug in ocular cul de sac. Polymeric nanoparticles for ocular purpose have potential in reducing the pulse entry and frequency of dosing, thus improving patient compliance. In the present study, mucoadhesive sodium alginate nanoparticles were developed for Brimonidine Tartrate (BT) as a model antiglaucoma drug by controlled ionic gelation technique. These nanoparticles would not only prolong drugs residence time but also reduce pulse entry in cul de sac. Nanoparticles were evaluated for morphology, surface characteristics, drug polymer interactions, particle size, polydispersibility index, zeta potential, entrapment efficiency, in vitro release profile and in vivo efficacy. The effect of various stabilizers on stabilization of blank and drug loaded nanoparticles was investigated. Irregular shape and loss of crystallinity for BT loaded sodium alginate nanoparticles was observed by TEM and SEM images respectively. IR spectra and DSC thermograms revealed the physicochemical interaction was involved during sodium alginate nanoparticle formation and entrapment of BT. The developed nanoparticles have average particle size of 450nm with PI 0.65, the entrapment efficiency ranged from 4-18 % and zeta potential values ranged from -27.5 mV to -24.1 mV. In vitro release profile showed a gradual drug release over the period of 3 hrs. In-vivo experiments showed that it was possible to prolong the drug release over a period of 8 hr, on topical instillation of BT loaded nanoparticles to albino rabbits, hence reducing the dosage frequency.

Effect of stabilizers on the tolerance of copper nanopowders for oxidation by molecular oxygen

The effect of various stabilizers, phenol, 1-naphthol, hydroquinone, hydroxylamine sulfate, metol, guanidine, and dimethylphenylbenzylammonium chloride, on the rate of oxidation of copper nanopowders by molecular oxygen was studied.

Infrared study of the photochemical behaviour of aromatic poly(ether urethanes): effect of various stabilizers

AbstractThe influence of various additives on poly(ether-urethane) UV stability is evaluated. The extent of the photo degradation has been studied by FTIR spectroscopy. The photo-stabilizer 2-hydroxy-benzophenone decreases the photooxidation on both hard and soft segment, whereas the effect of the phenolic antioxidant 2,6-di-t-butyl-4-hydroxytoluene is more significant on the soft segment. However, the effect of the nickel chelate, 2,2’-thiobis(4-t-octylphenolate)-nbutylamine of nickel, depends on the polyurethane nature.

Stabilization of Hard Gelatin Capsule Shells Filled with Polyethylene Glycol Matrices

The purpose of this study was to evaluate the effects of various stabilizers on the dissolution stability of liquid-filled capsule dosage forms containing a potent drug dissolved in polyethylene glycols. A systematic dissolution slowdown was observed in gelatin capsule formulations without a stabilizer and was exaggerated under stress storage conditions. This slowdown is attributed to cross-linking of the gelatin shells. Addition of butylated hydroxyanisole (BHA) delayed the onset of gelatin cross-linking, and a combination of BHA with water added to this formulation effectively prevented product dissolution slowdown. For similar formulations filled into hypromellose capsule shells, no dissolution slowdown was observed, even in the absence of stabilizers.

Effect of Various Stabilizers on Whey Separation (Syneresis) and Quality of Yoghurt

This study was carried out to investigate the effect of various stabilizers on whey separation (syneresis) and the quality of set yoghurt. Yoghurt was prepared by using seven various stabilizers like pectin, guargum, carboxymethyl cellulose (CMC), carrageenan, sodium alginate, cornstarch and gelatin @ 0.4% in milk containing 3.5% milk fat and total solids 16.6%. Various determinations such as pH, acidity, lactose and syneresis level were made at 0, 5, 10 and 15 days of storage interval. It was observed that there was gradual decrease in pH and increase in acidity in all samples during 15 days at 10 degree centigrade plus-minus 1. Lactose contents decrease in all Yoghurt samples during storage due to its conversion into lactic acid. It was observed that cornstarch tend to reduce syneresis followed by gelatin, pectin, guargum, CMC, Carrageenan, sodium alginate while comparing with control.

Influence of various stabilizer systems on the ageing behavior of PE–MD—II. Ageing of pipe specimens in air and water at elevated temperatures

In this series of five papers an attempt is undertaken to study systematically the effect of various stabilizers and stabilizer systems on the long-term ageing behavior of a given medium density poly(ethylene) type (PE–MD) under various environmental and mechanical loading conditions. In Part I, the effect of hot water ageing at temperatures of 95 and 105°C on changes in the degree of crystallinity, on the residual thermo-oxidative stability, and on uniaxial tensile properties was described for seven different PE–MD/stabilizer compounds. Part II of this series extends these studies for two materials (unstabilized PE–MD and PE–MD containing a primary/secondary antioxidant mixture) over a wider temperature range from 40 to 105°C, including both air and water exposure. Thermo-analytical measurements to characterize the residual thermo-oxidative stability in terms of oxidation temperature and oxidation induction time together with high performance liquid chromatography (HPLC) were carried out to provide more insight into the underlying mechanisms of ageing in both environments. In contrast to Part I, where compression molded specimens were used, extruded pipe specimens were produced for the investigations described in Part II to more closely resemble the situation of practical pipe applications.

E.S.R. Investigations of Polypentenamers Degradation

Abstract Electron spin resonance investigations of the thermo-oxidative degradation of trans-polypentenamer rubbers, containing various stabilizers, are reported. The dependence of the resonance line parameters on the degradation time and temperature as well as the effect of various stabilizers on the resonance line are studied in detail. The activation energies for the generation of free radicals, the reaction order for the overall generation of free radicals and the associated constant rate, are estimated.

III. Chemical compatibility study of gap based propellant by the DVST

Abstract To produce a clean propellant, we must use new energetic materials, whose effect on the chemical stability during long-term storage is unknown. A formulation including ammonium nitrate (AN), GAP, and BDNPAF was studied. This study was based on accelerated aging and gas evolution, using the vacuum stability test in conjunction with gas chromatography. Incompatibility between AN and the other ingredients was found to be responsible for the chemical degradation. The effect of various stabilizers was evaluated and N-methyl-4-nitroaniline proved to be the most efficient stabilizer for the formulation investigated.