Development of Ciprofloxacin HCl-Based Solid Lipid Nanoparticles Using Ouzo Effect: An Experimental Optimization and Comparative Study

This study was performed to develop solid lipid nanoparticles of water soluble drug ciprofloxacin HCl using quick solvent diffusion evaporation technique (ouzo effect). A statistical central composite rotatable design was used to study the effect of independent variables. In the subsequent step, optimized SLN were further compared with nanostructured lipid carriers and nanoemulsion for particle size, zeta potential, drug entrapment, drug release, and stability. Comparative study revealed that the drug encapsulation efficiencies were enhanced by adding the Capmul MCM C8 into the solid lipid nanoparticles. The in vitro drug release study of all three formulations showed rapid release for nanoemulsion while controlled release for SLN. Stability study of all the formulation proved that nanostructured lipid carrier and SLN could prevent the drug expulsion during the storage period. Results of the study suggested that the SLN and nanostructured lipid carriers produced by the principle of ouzo effect could potentially be exploited for better drug entrapment efficiency and controlled drug release of water soluble actives.     

Microencapsulation of Calcium Using Water-in-Oil-in-Water Double Emulsion Method

Calcium in the form of tricalcium phosphate was encapsulated in the inner water phase of water-in-oil-in-water emulsion. Efficiency and payload of microcapsules were optimized using a D-optimal mixture design with four components (gelatin, agar, primary water-in-oil emulsion, and water in outer phase). Release profiles of calcium from microcapsules were determined at 4°C over 12 days. It was found that microencapsulation efficiency increased by increasing of water-in-oil emulsion to 45% and then decreased at higher contents of this portion. However, payload increased continuously with increase of water-in-oil fraction. Less calcium was released when both biopolymers and water-in-oil emulsion contents were increased.     

Improvement of Sweep Efficiency by Alkaline Flooding for Heavy Oil Reservoirs

Severe viscous fingering during water flooding of heavy oil leaves a large amount of oil untouched in the reservoir. Improving sweep efficiency is vital for enhancing heavy oil recovery. This study presented a laboratory study for improving sweep efficiency by alkaline flooding in heavy oil Reservoirs. This included glass-etched micromodel flooding tests, one-dimensional flooding experiments and three-dimensional physical model study. The micromodel tests show that W/O droplet flow plays a prominent role in the alkaline flooding to improve sweep efficiency. There is a minimum alkaline concentration that generates the W/O droplet flow, and the W/O droplet flow is more obvious with the alkaline concentration increasing. A series of flood tests were conducted using 325 mPa · s, 2000 mPa · s, and 3950 mPa · s heavy oils to assess the effectiveness of W/O droplet flow in alkaline flooding for enhanced heavy oil recovery. The flood tests results demonstrate the considerable potential for improved heavy oil recovery by alkaline flooding, and moreover, the incremental oil recovery has been found to increase as the alkaline concentration increases. The result obtained in three-dimensional physical model study indicates that the sweep area can be greatly improved by the formation of W/O droplet flow in alkaline flooding.     

Stability of W/O Emulsions Encapsulating Polysaccharides

In the frame of formulation of W/O emulsions entrapping polysaccharides devoted to agricultural applications, the aim of this work was to study the stability over time of these emulsions, stabilized with either soybean lecithin or polyglycerol polyricinoleate (PGPR) as emulsifiers. Emulsifiers were dissolved in oil phase, and polysaccharides (carboxymethycellulose (CMC), guar, xanthan) in ultrapure water. Emulsions stability was studied through natural aging tests and accelerated aging tests, using bottle tests, microscopy and calorimetry. Experiments showed that PGPR was more efficient than lecithin to stabilize emulsions containing the polysaccharides studied, and that emulsions prepared with CMC showed the best stability.     

Cinnamoyl Alginate Microspheres: Effect of UV-Treatment on Release of FITC-Dextran

Cinnamoyl alginate microspheres were prepared using the water droplets of W/O emulsions as a template. Cinnamoyl alginates having variable content of the cinnamoyl group were prepared by a condensation reaction. The photo-dimerization degree of the cinnamoyl group increased as the molar ratio of pyranose unit/cinnamoyl group increased from 1:0.043 to 1:0.18. The air/water interfacial activity of cinnamoyl alginate also increased with increasing the molar ratio. Aqueous solution of cinnamoyl alginate was dispersed in mineral oil to obtain W/O emulsion. UV light (254 nm, 6 W) was irradiated to the emulsion to dimerize the cinnamoyl groups, and CaCl₂ was added to the emulsion to cross-link the cinnamoyl alginate. The surface of UV-treated microspheres was rougher than that of UV-untreated microspheres, possibly due to the photo-dimerization-induced tension on the alginate chains. The release degrees for 24 hours of fluorescein isothiocyanate-dextran (FITC-dextran; MW 4000) from UV-treated microspheres were markedly higher than those from UV-untreated ones. This is possibly due to the intramolecular dimerization of cinnamoyl group. The UV irradiation-induced percentage increase in the maximum release degree was greater as the content of cinnamoyl group was higher.     

Effect of Nanoparticle Hydrophobicity on Stability of Highly Concentrated Emulsions

The effect of hydrophobicity index (HI) of fumed nanosilica specimens on stability of water-in-oil (W/O) highly concentrated emulsions (HCE with ? = 90 vol%) with an overcooled dispersed phase was studied. A series of five silica with HI in the 0.60–1.34 range and HI > 3 were used separately and in combination with a low molecular weight traditional surfactant, Sorbitan MonoOleate (SMO). First, it was shown that SMO alone can stabilize W/O HCE whereas only silica nanoparticles with intermediate HI in the range 0.97 ≤ HI ≤ 1.34 could form W/O emulsions only up to 77–79 vol%. Then, on the contrary to SMO-based emulsions, Pickering emulsions are unstable under shearing. When mixed (silica plus SMO) emulsifier systems were used, firstly a thermodynamic consideration revealed that only SMO is likely to adsorb at the W/O interface and controls the emulsifying process by the decrease in the interfacial tension. Then, interestingly, all different kinds of emulsion stability investigated in this study demonstrate a breaking point (BP) at HI = 0.97. Below the BP the emulsions were found to be very unstable on shelf as well as under shear. Above the BP, a clear synergy between colloidal silica and SMO surfactant has been found.      

Smart Determination of Difference Index for Asphaltene Stability Evaluation

Precipitation and deposition of asphaltene during different stages of petroleum production is recognized as problematic in oil industry because of the increase in production cost and the inhibition of a consistent flow of crude oil in different medium. Numerous correlations have been developed to determine asphaltene stability in crude oil. In this study, a novel ONN method was used to estimate difference index from SARA fraction data for rapid, accurate, and cost-effective determination of asphaltene stability. Neural networks are highly in danger of trapping in local minima. To eliminate this flaw, a hybrid genetic algorithm-pattern search technique was used instead of common back-propagation algorithm for training the employed neural network. A comparison between neural network and optimized neural network indicated superiority of optimized neural network.      

Surfactant-Free Multiple Pickering Emulsions Stabilized by Combining Hydrophobic and Hydrophilic Nanoparticles

A series of W/O/W or O/W/O emulsion stabilized solely by two different types of solid nanoparticles were prepared by a two-step method. We explored the option of particular emulsifiers for the multiple Pickering emulsions, and a variety of nanoparticles (silica, iron oxide, and clay) only differing in their wettability was used. The primary W/O emulsion was obtained by the hydrophobic nanoparticles, and then the hydrophilic nanoparticles were used as emulsifier in the secondary emulsification to prepare the W/O/W emulsion. In a similar way, the primary O/W emulsion of the O/W/O emulsion was stabilized by the hydrophilic nanoparticles, while the secondary emulsification to prepare the O/W/O emulsion was effected with the hydrophobic nanoparticles. The resultant multiple Pickering emulsion was stable to coalescence for more than 3 months, except the W/O/W emulsions of which the secondary emulsion stabilized by clay nanoparticles became a simple O/W emulsion in a day after preparation. Moreover, the temperature and pH sensitive poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAm-co-MAA)) microgels were introduced as an emulsifier for the secondary emulsification to obtain the stimulus-responsive multiple W/O/W emulsion. Such microgel-stabilized multiple emulsions could realize the efficient controlled release of water-soluble dye, Rhodamine B (RB) on demand in a multiple-emulsion delivery system.      

A DOE Approach to Investigate the Influence of Process-Parameters and Composition on the Stability of Emulsions Stabilized by Marine Polysaccharides Prepared by High-Pressure Homogenization

The influence of pre-homogenization conditions (speed and duration at a rotor–stator system), homogenization pressure, and quantitative composition of the emulsions on the droplet size and stability of the resulting emulsions is investigated using design of experiments. A mix of marine polysaccharides (e.g., alginate and fucoidane) from Ascophyllum nodosum is used as emulsifier to form O/W-emulsions with medium-chained triglycerides. It was found that the amount of emulsifier is the most relevant parameter for emulsions' stability whereas the influence of the homogenization pressure is more distinct at low polysaccharide contents. In contrast, the parameters of pre-homogenization do not influence the droplet size significantly.      

Effect of Water Fraction on Rheological Properties of Waxy Crude Oil Emulsions

This article discusses the effect of water fraction on the rheological properties of waxy crude oil emulsions including gel point, yield stress, viscosity, and thixotropy. The experimental results reveal that the rheological behaviors of the w/o emulsion samples all intensify with the increase of water volume fraction within 60%. Of more significance is that a correlation for w/o emulsions between yield stress and water volume fraction is put forward with an average relative error of 6.75%. In addition, some mainstream viscosity prediction models of w/o emulsions are evaluated, and Elgibaly model is the best-fit for the emulsions in this study.     

Influence of Hydrophobically Associating Polyacrylamide on Dispersion Property of Water-Soluble Phenol-For-maldehyde Resin

To improve dispersion stability of water soluble phenol-fomaldehyde resin (PFR) in relatively low salinity water, the effect of hydrophobically associating polymer (HAP) on the dispersion property of PFR in NaCl solution was studied by the measurement of the size and zeta potential of PFR, HAP, and PFR/HAP molecule aggregates in NaCl solution, and the turbidity of PFR and PFR/HAP dispersions. The results show that due to the hydrophobically group on HAP molecule has similar structure as molecular structure of PFR and stronger hydrophobically association of HAP molecules in NaCl solution, HAP, and PFR molecules can form complex molecule aggregates together. The formation of the complex molecule aggregates enhanced the stability of PFR dispersion in NaCl solution.     

Study of Interactions and Association Thermodynamics Between Sudan Red and Sodium Dodecyl Sulfate in Microemulsions

The absorption spectrum of Sudan red III (SR) in oil solutions and a series of O/W microemulsion with surfactant sodium dodecyl sulfate (SDS) has been determined by the UV-Vis spectrophotometer. We found that an association interaction existed between the stain SR and anionic surfactant SDS in water/mixed oil/SDS microemulsions. By measuring the absorbance of Sudan red in a series of microemulsions which has different R values and using the appropriate association models to analyze the experimental data, we obtain the association constants of SR and SDS, and the values of thermodynamics functions of associationΔ_r G _m has also been calculated from the association constants.     

Castor Oil Based Organogels: I. Synthesis,Swelling, and Network Parameters

Linear and branched polyesters were prepared by transesterification of methyl recinoleate without or with diethylene glycol, trimethylol propane or pentaerithirtol for different durations. Molecular weight of the synthesized polyesters were determined using gel permeation chromatography and hydroxyl number. Their chemical structure were characterized by FTIR. Crosslinked polyesters were prepared using different weight ratios of trimethylolpropane triacrylate in presence of benzoyl peroxide initiator. These organogels were characterized through soluble fraction and toluene sorption capacity. Swelling kinetics and network parameters including polymer solvent interaction, effective and theoretical crosslink densities, average molecular weight between crosslinks and modulus of elasticity were determined.     

Factors in the Single-Step Bulk Process Preparation of a Triple Janus Emulsion

Some factors in the preparation of triple Janus emulsions in a single-step bulk process were investigated using optical microscopy. The emulsions consisted of water, O.097 weight fraction, a commercial surfactant, Tween 80, 0.03 weight fraction, a vegetable oil (VO), 0.18 weight fraction, and a silicone oil (SO), 0.72 weight fraction. A surprising connection was found between the state of the compounds prior to mixing and the final morphology as well as stability of the emulsion. Separately adding the compounds or with the surfactant dissolved in the vegetable oil, prior to mixing, did not result in a Janus emulsion. Instead, simpler emulsions with limited stability were attained even with prolonged mixing. Storing the compounds together without mixing for two days followed by mixing resulted in a Janus emulsion in which the (VO + SO)/W/VO drops were more sparsely populated with Janus drops, and emulsion stability was limited. Finally, preparing the emulsion from the aqueous surfactant solution and the two oils gave a (VO + SO)/W/VO/SO emulsion with the W drops heavily populated by Janus drops and with improved stability.