Aqueous Dispersed Systems Research Articles

Development of Enteric Diclofenac Sodium Microparticles Through a Spray-Drying Process Facilitated by Different Aqueous Dispersion Systems

The objective of this study was to prepare enteric diclofenac sodium microparticles using an aqueous dispersion system via spray-drying. Two aqueous-based solvent systems, phosphate buffer at pH 7.0 and ammonium hydrogen carbonate solution, were employed as the feed dispersion media in the spray-drying process based on the solubility characteristics of Eudragit® L100. At a drug-to-polymer ratio of 1:1, the optimal solids concentration in the feed dispersion was determined to be 2% w/v, as it enabled an approximately 5-30 µm smooth-surfaced spherical microparticle with a high production yield. Diclofenac sodium was efficiently encapsulated within the microparticles, existing as solid dispersion in a partially amorphous form. Notably, the spray-drying conditions utilized in this study obviated the need for further heating for microparticles prepared using ammonium hydrogen carbonate solution, as the residual ammonium could be completely eliminated during the spray-drying process. The two-stage biorelevant drug release profile of enteric microparticles demonstrated their ability to inhibit drug dissolution under acidic conditions while facilitating drug release under basic conditions. The phosphate buffer-based microparticles exhibited greater protection efficiency under acidic conditions compared to ammonium hydrogen carbonate-based systems, despite residual alkaline salt being present in the microparticles. These results validate the potential of the developed microparticles for use as an enteric drug delivery system.

Unified approach for describing rheological behavior of soil and mineral substrates modified with polymers

Studies in the rheology of natural aqueous dispersions (soils and their mineral substrates) as well as the approaches to control rheological parameters of these systems are of the prime importance to progress in the modern agricultural technologies, geoengineering, construction, etc. To advance in these fundamental and applied directions both original processing of the experimental results and search for the promising modifying agents are required. In this paper, rheological behavior of a representative range of virgin and modified aqueous soils, quartz sand and clays was studied. Modification of the above aqueous dispersed systems with polyelectrolytes and their complexes provided variation of the basic viscoelastic parameters corresponding to the linear viscoelastic region (initial storage modulus G0′, initial loss modulus G0", and strain γ0) and to the transition to steady-state flow (storage modulus Gin′ and strain γin) within 1 – 2 orders of magnitude. For samples studied, correlations for these mechanical characteristics were found – with the growth in the values of G0′ and G0′′, the increase in the values of Gin′ and decrease in the values of γ0 and γin were observed. Based on these correlations the master curves for the strain dependences of storage and loss modulus as well as for loss tangent were constructed. The appearance of the master curves reflected the unified regularities of the rheological response of dispersed systems which were attributed to the general features of structural evolution caused by the mechanical loading. Procedure for prediction of the rheological behavior of aqueous soil samples based on the experimental measurement of only two experimental characteristics (initial values of storage and loss modulus G0′ and G0′′ respectively) was proposed. The validity of this approach was tested using independent experimental data. The original approach obtained can be used for express analysis of the rheology of natural aqueous dispersed materials.

Effects of soybean β-conglycinin subunits composition on its emulsifying properties and the mechanism

In the soybean β-conglycinin system, subunit composition has an important influence on its emulsification properties. To elucidate the mechanism of subunit action in the emulsification process, the separated and purified β-subunit and the mixture α- and α′-subunits (referred to αα′-subunit) were remixed in varying proportions, and then the physicochemical properties and structural properties of the subunit emulsifying system were characterized. The results demonstrated that when the ratio of αα'-subunit to β-subunit was 5:5, the subunit aqueous dispersion system exhibited a minimum particle size of 47.58 nm, a maximum solubility of 87.21%, and the emulsification stability and emulsification activity were also optimal. Scanning electron microscope (SEM) images revealed excellent cross-linking between αα′-subunit and β-subunit, forming a protein network structure that provided a structural basis for its emulsification. The emulsion with a subunit ratio of 5:5 exhibited the highest fraction of interfacial protein adsorption of 23.43% and the largest interfacial protein concentration of 11.79 mg/m2. Inter-subunit adsorption and emulsion formation were primarily driven by hydrophobic interactions, with the β-subunit exhibiting a higher affinity for adsorption than the αα′-subunit. The action mechanism of the subunits in the emulsion formation was proposed as a “three-stage” process, including establishing an initial weak protein network structure within the aqueous dispersion, followed by developing an emulsion interface layer and ultimately culminating in forming an emulsion gel network structure. Elucidating the emulsifying mechanism at the subunit level is crucial for enhancing the theoretical framework of soybean protein emulsification.

Novel Modified Styrene-Based Microspheres for Enhancing the Performance of Drilling Fluids at High Temperatures.

Ensuring wellbore stability is of utmost importance for safety when drilling in deep formations. However, high temperatures severely disrupt the drilling fluid gel system, leading to severe stability issues within ultra-deep formations containing micropores. This study focused on the development of a polymer-based plugging material capable of withstanding high temperatures up to 200 °C. A kind of microsphere, referred to as SST (styrene-sodium styrene sulfonate copolymer), was synthesized with a particle size of 322 nm. Compared to polystyrene, the thermal stability of SST is greatly improved, with a thermal decomposition temperature of 362 °C. Even after subjecting SST to hot rolling at 200 °C for 16 h, the particle size, elemental composition, and zeta potential remained stable within an aqueous dispersion system. The results of core displacement and NMR tests demonstrate that SST considerably reduces the pore diameter with a remarkable plugging efficiency of 78.9%. Additionally, when drilling fluids reach 200 °C, SST still enhances drilling fluid suspension and dispersion, and reduces fluid loss by over 36% by facilitating the dispersion of clay particles, improving the gel structure of the drilling fluid, resisting clay dehydration, and promoting plugging. The development of SST provides valuable insights into the preparation of high-temperature-resistant microspheres and the formulation of effective plugging agents for deep-well drilling fluids.

Measurement Precision and Thermal and Absorption Properties of Nanostructures in Aqueous Solutions by Transient and Steady-State Thermal-Lens Spectrometry

A simultaneous steady-state and transient photothermal-lens modality was used for both the thermal and optical parameters of aqueous dispersed systems (carbon and silica nanoparticles, metal iodides, surfactants, heme proteins, albumin, and their complexes). Heat-transfer parameters (thermal diffusivity and thermal effusivity), the temperature gradient of the refractive index, light absorption, and concentration parameters were assessed. To simultaneously measure thermal and optical parameters, the time scale of thermal lensing (characteristic time, tc) should correspond to an excitation beam size of 60–300 µm, and the relative time intervals 0.5÷5tc and (5÷20)tc should be selected for transient and steady-state measurements, respectively. Dual-beam thermal-lens spectrometers in a mode-mismatched optical schematic at various excitation wavelengths were built. The spectrometers implement back-synchronized detection, providing different measurement conditions for the heating and cooling parts of the thermal-lens cycle. By varying the measurement parameters depending on the dispersed system, the conditions providing the suitable precision (replicability, repeatability, and reproducibility) of thermal-lens measurements were found; setups with a broad excitation beam (waist size, 150 and 300 μm) provide longer times to attain a thermal equilibrium and, thus, the better precision of measurements of thermal diffusivity.

High water-stable, hard and strong-adhesive antistatic films from waterborne PEDOT:PSS composites

Electrostatic discharge (ESD) protection is quite necessary for the electronic industry and modern life. Antistatic materials based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) have been widely used in these fields such as electronic devices, smart windows, specialty papers, photographic films, glass coatings, fabrics and so on. To solve the critical shortcomings of PEDOT:PSS in high commercial price, high water absorption accompanying dramatically decreased structure stability, mechanical damage vulnerability, and insufficient substrate adhesion ability, etc., herein, we prepared an antistatic PEDOT:PSS/Epoxy films from self-made PEDOT:PSS aqueous dispersion and waterborne epoxy system by facile mechanical mixing and drop-casting on glass substrates. The surface morphology, volume resistivity, surface wettability and water immersion stability of these films were systematically studied. In addition, the substrate adhesion and surface hardness of the films after the introduction of polyhedral oligomeric silsesquioxane (POSS) and silane coupling agent (SCA) in such composite systems were investigated. The optimized PEDOT:PSS/Epoxy/POSS/SCA films exhibited fine antistatic ability, increased hydrophobicity, improved water stability, high hardness (HB) and good adhesion (level 1) on glass substrates. Such conductive films together with their design principle and their environmentally friendly waterborne mother dispersions will promote the further use of PEDOT:PSS in ESD protection materials or others in organic film electronics including vigorously developed flexible and wearable electronic devices.

Selective copper-catalysed atom transfer radical addition (ATRA) in water under environmentally benign conditions.

Simple and green conditions for copper-catalysed ATRA reactions in water have been developed. Firstly, [Cu(ADPA)(H2O)(ClO4)2] (1b, ADPA = 9-[(2,2'-dipicolylamino)methyl]anthracene) was demonstrated to be capable of selectively catalysing the ATRA of CCl4 to styrene using L-ascorbic acid (AsH2) as a reducing agent in organic solvent mixtures under ambient atmosphere. Mechanistic investigation suggested that our ATRA reaction proceeded via a single-electron transfer (SET) mechanism through an inner-sphere complex, which is consistent with the widely accepted mechanism for copper-catalysed ATRA. To perform the reaction in water as a sole solvent, a biocompatible surfactant (2 wt% Tween 20 or Tween 80) was added to improve solubility and increase the local concentration of organic reagents and the copper catalyst. Without the need for a complicated oxygen-free set-up, the ATRA reaction catalysed by this simple aqueous-dispersed system can be performed at a mild temperature (60 °C) and a relatively short reaction time (6 h) using 1 mol% of the catalyst. Furthermore, this facile protocol is also applicable for other alkene substrates demonstrated in this work, resulting in satisfactory to excellent substrate conversion and product yields.

КОМБІНОВАНІ РОЗЧИНИ НЕРОЗЧИННИХ У ВОДІ БІОЛОГІЧНО АКТИВНИХ СПОЛУК З ВИКОРИСТАННЯМ БІОСУРФАКТАНТІВ

Solutions of biologically active substances insoluble in water (thiosulfoesters, anthraquinone derivatives, pyrazoline) were obtained using a combined solvent and biogenic surfactants. For this purpose were used rhamnolipids, their biocomplex with polysaccharides synthesized by the Pseudomonas SP strain. PS-17, trehalosolipids of the Rhodococcus erythropolis AU-1 strain, and the commercial biosurfactant surfactant. Aqueous dispersed systems of the studied substances were also obtained. The research results have prospects for use in pharmacy.

Application of Vinyl ether Copolymers for Surface Modification of Carbon Black

In this work, the possibility of stabilizing aqueous dispersed systems of carbon with vinyl ether copolymers of various composition and structure was investigated. It was shown that the presence of hydrophobic fragments in the macromolecule chain plays a significant role and positively affects the results of stabilization of aqueous dispersions of carbon particles. It was shown that the composition and molecular architecture of the stabilizing copolymer strongly affects the stabilizing ability in studied systems. Studies have shown that the use of a polymeric stabilizer in combination with ultrasonic treatment of dispersed systems makes it possible to obtain stable, homogeneous, highly dispersed suspensions. At the same time, it was demonstrated that a strong increase in the time and intensity of ultrasonic treatment of the system does not lead to a significant improvement in the results

Stabilization of Aqueous Dispersions of Inorganic Microparticles Under Mechanical Activation

The stability of aqueous dispersed systems of TiO2 and Fe2O3 microparticles in the presence of a water-soluble polymer - ethylhydroxyethylcellulose (EHEC) - has been studied under the condition of using two methods of mechanoactivation of the pigment surface - processing them in a disintegrator and in an ultrasonic field. It is shown that in the absence of a polymer stabilizer, an intense effect on aqueous dispersed systems of pigments leads to rapid coagulation of particles. In the presence of EHEC, a small stabilizing effect is observed, which is significantly enhanced when processing dispersed systems in a disintegrator and in an ultrasonic field. In this case, the stability of dispersed systems depends little on the method of mechanoactivation of their surface, but significantly depends on the duration of the intense exposure.

Fluorescence characteristics of aqueous dispersed systems of succinic acid as potential markers of their self-organization and bioeffects in low concentration range

Abstract The issue of protecting aquatic ecosystems from biologically active compounds (BACs) such as pesticides and pharmaceuticals detected in aquatic environments at low concentrations has become urgent. Presently, literature provides much information about BACs that at low concentrations cause significant damage to hydrobionts, but a physicochemical explanation for these phenomena has appeared only relatively recently. Experimental findings have shown that diluted aqueous solutions of BACs are self-organized disperse systems, whose disperse phase (nanoassociates) rearranges upon dilution, which is accompanied by nonmonotonous changes in the physicochemical and biological properties of the system. This work introduces the study of fluorescence and UV absorption of aqueous diluted systems of a biogenic succinic acid (SA), used as an antihypoxic and antioxidant pharmaceutical. It is shown for the first time that the fluorescence spectra ( λ e x at 225 nm) of SA systems are informative at the calculated concentrations range from 1 ⋅ 10−17 to 1 ⋅ 10−5 M. The nonmonotonous concentration dependence of fluorescence intensity ( λ e x at 225 nm, λ e m at 350 nm) is in good agreement with the data on nanoassociates’ size, as well as with both the physicochemical properties of SA systems and their biotesting results, which were obtained using the certified procedures for monitoring the toxicity of natural waters and wastewater. The observed coherence between the fluorescence intensity of SA systems and the nanoassociates’ size allows for the conclusion that it may be possible to consider fluorescence as a potential marker of self-organization and bioeffects of diluted aqueous BACs systems.

Co-Delivery of Imiquimod and Curcumin by Nanoemugel for Improved Topical Delivery and Reduced Psoriasis-Like Skin Lesions.

The current investigation aimed to improve the topical efficacy of imiquimod in combination with curcumin using the nanoemulsion-based delivery system through a combinatorial approach. Co-delivery of curcumin acts as an adjuvant therapeutic and to minimize the adverse skin reactions that are frequently associated with the topical therapy of imiquimod for the treatment of cutaneous infections and basal cell carcinomas. The low-energy emulsification method was used for the nano-encapsulation of imiquimod and curcumin in the nanodroplet oil phase, which was stabilized using Tween 20 in an aqueous dispersion system. The weak base property of imiquimod helped to increase its solubility in oleic acid compared with ethyl oleate, which indicates that fatty acids should be preferred as the oil phase for the design of imiquimod-loaded topical nanoemulsion compared with fatty acid esters. The phase diagram method was used to optimize the percentage composition of the nanoemulsion formulation. The mean droplet size of the optimized nanoemulsion was 76.93 nm, with a polydispersity index (PdI) value of 0.121 and zeta potential value of −20.5 mV. The optimized imiquimod-loaded nanoemulsion was uniformly dispersed in carbopol 934 hydrogel to develop into a nanoemulgel delivery system. The imiquimod nanoemulgel exhibited significant improvement (p < 0.05) in skin permeability and deposition profile after topical application. The in vivo effectiveness of the combination of imiquimod and curcumin nanoemulgel was compared to the imiquimod nanoemulgel and imiquimod gel formulation through topical application for ten days in BALB/c mice. The combination of curcumin with imiquimod in the nanoemulgel system prevented the appearance of psoriasis-like symptoms compared with the imiquimod nanoemulgel and imiquimod gel formulation entirely. Further, the imiquimod nanoemulgel as a mono-preparation slowed and reduced the psoriasis-like skin reaction when compared with the conventional imiquimod gel, and that was contributed to by the control release property of the nano-encapsulation approach.

Low Ppm Atom Transfer Radical Polymerization in (Mini)Emulsion Systems.

In the last decade, unceasing interest in atom transfer radical polymerization (ATRP) has been noted, especially in aqueous dispersion systems. Emulsion or miniemulsion is a preferred environment for industrial polymerization due to easier heat dissipation and lower production costs associated with the use of water as a dispersant. The main purpose of this review is to summarize ATRP methods used in emulsion media with different variants of initiating systems. A comparison of a dual over single catalytic approache by interfacial and ion pair catalysis is presented. In addition, future development directions for these methods are suggested for better use in biomedical and electronics industries.

To the Question of Structure Formation of Dispersed Systems in Cement Technology

In the this publication, readers will find the results of the analytical and experimental research into the physical and chemical processes in the consecutive formation of structures at the major technological stages of the present-day production of portland cement. Dispersed systems of raw mixtures, which in different methods of production are formed at the stage of grinding, mixing and homogenization of raw materials, belong to different classification groups. In wet and combined methods is produced cement sludge - aqueous dispersed system, which belongs to the 2nd group: two-phase systems such as solid dispersed phase - liquid dispersion medium. In the dry method dispersed system is formed, which belongs to the 3rd group: three-phase systems such as solid dispersed phase - water-liquid and air-gas dispersion medium. The structural-mechanical and rheological properties of the coagulation structure of cement slurries, wich differ in the main raw material components, are shown. The study of deformation processes of aqueous dispersed systems showed that the nature of the development of deformations - rapid elastic ε₀’, slow elastic ε₂’ and plastic ε₁’τ sludge samples belong to different structural - mechanical types. At the same time differences in quantitative values and a ratio of the specified types of deformation are noted. Readers will also find the particularities of the phase changes in the process of the crystallization structure formation at baking to maximum temperature 1450°С.

An environment-friendly fabrication of nano-Co3O4 coating by aqueous electrophoretic deposition

Co3O4 coating is one of most studied transition metal oxide due to its wide application in many fields such as gas sensors, electrochromic thin films, supercapacitors, and solar selective absorber. Aqueous electrophoretic deposition (EPD), which is considered as a cost-effective and environment-friendly coating technology, was successfully employed in preparing nano-Co3O4 coating in this study. For the EPD process with the solid loading of 1 g L−1, 2.0 mM nitric acid was employed as suitable additive and 5 V was employed as deposition voltage. The prepared nano-Co3O4 coating exhibited good film characteristics, which was proved by scanning electron microscopy (SEM) technology. The result suggests that a rapid preparation of nano-Co3O4 coating in aqueous dispersion system can be easily accomplished. Moreover, the optimum concentrations of the added nitric acid would increase with the solid loading of Co3O4 nanoparticle, but the growth rate of the former was obviously lower than that of the latter.

Photopolymerization synthesis of polyacrylic acid dispersant with methoxysilicon end groups and its application in a nano‐SiO2 aqueous system

AbstractIn order to improve the dispersity and stability of the nano‐SiO2 aqueous system with high solid content, a kind of polyacrylic acid dispersant with methoxysilicon end groups (KH590‐PAA) was synthesized by photopolymerization of acrylic acid (AA) initiated with (3‐mercaptopropyl)trimethoxysilane (KH590). After adding KH590‐PAA into the nano‐SiO2 aqueous dispersion system (20 wt% solid content), the viscosity and the curing time of the system were measured with a rotational viscometer and the inverted bottle method. Moreover, the dispersion mechanism of KH590‐PAA for the nano‐SiO2 aqueous system was researched by measuring the adsorption capacity, the particle size and the zeta potential of the nanoparticles with a conductivity meter, dynamic light scattering, SEM and TEM, respectively. The results showed that the methoxysilicon groups in KH590‐PAA could react with hydroxyl groups on the surface of nano‐SiO2 in the process of stirring, which enhanced the adsorption capacity of the dispersant and then increased the surface charge of the particles. Therefore, electrostatic repulsion and steric hindrance effects between the SiO2 nanoparticles could be further enhanced by adding the KH590‐PAA dispersant, and then the nano‐SiO2 aqueous system exhibited better dispersity and stability. Besides, the dispersion properties of SiO2 nanoparticles in water were closely related to the addition amount and the molecular weight of the KH590‐PAA dispersant. © 2018 Society of Chemical Industry

Fabrication of nanocellulose/PEGDA hydrogel by 3D printing

PurposeNanocellulose is characterised by favourable biocompatibility, degradability, nanostructure effect, high modulus and high tensile strength and has been widely applied in various fields. The current research in the field of new nanocellulose materials mainly focuses on the hydrogel, aerogel and the tissue engineering scaffold. All of these are three-dimensional (3D) porous materials, but conventional manufacturing technology fails to realise precise control. Therefore, the method of preparing structural materials using 3D printing and adopting the nanocellulose as the 3D printing material has been proposed. Then, how to realise 3D printing of nanocellulose is the problem that should be solved.Design/methodology/approachBy adding the photosensitive component polyethyleneglycol diacrylate (PEGDA) in the aqueous dispersion system of nanocellulose, the nanocellulose was endowed with photosensitivity. Then, nanocellulose/PEGDA hydrogels were prepared by the additive manufacturing of nanocellulose through light curing.FindingsThe results showed that the nanocellulose/PEGDA hydrogels had a uniform shape and a controllable structure. The nanocellulose supported the scaffold structure in the hydrogels. Prepared with 1.8 per cent nanocellulose through 40 s of light curing, the nanocellulose/PEGDA hydrogels had a maximum compression modulus of 0.91 MPa. The equilibrium swelling ratio of the nanocellulose/PEGDA hydrogel prepared with 1.8 per cent nanocellulose was 13.56, which increased by 44 per cent compared with that of the PEGDA hydrogel without nanocellulose.Originality/valueThe paper proposed a method for rapidly prototyping the nanocellulose with expected properties, which provided a theoretical basis and technological reference for the 3D additive manufacturing of nanocellulose 3D structure materials with a controlled accurate architecture.

Characterisation of Andalusian peats for skin health care formulations

Abstract Composition and properties of three different peat strata from “El Padul” peatbog have been studied and peat pastes have been formulated to prepare skin health care products. As for composition, the main phase of each stratum was constituted of smectites (outer stratum), organic matters (intermediate) or carbonates (inner). Pristine strata and their aqueous dispersed systems were characterized for such properties (pH, rheology and cooling kinetics) that are considered determinant in view of their topical application. Main phases of each stratum influenced pH and rheology but not cooling kinetics. Combination of the strata in different w/w ratios led to peat pastes with improved performance for skin administration.

Surface-Enhanced Resonance Raman Scattering of Rhodamine 6G in Dispersions and on Films of Confeito-Like Au Nanoparticles.

Surface-enhanced resonance Raman scattering (SERRS) of rhodamine 6G was measured on confeito-like Au nanoparticles (CAuNPs). The large CAuNPs (100 nm in diameter) in aqueous dispersion systems showed stronger enhancing effect (analytical enhancement factor: over 105) of SERRS than the small CAuNPs (50 nm in diameter), while the spherical Au nanoparticles (20 nm in diameter) displayed rather weak intensities. Especially, minor bands in 1400–1600 cm−1 were uniquely enhanced by the resonance effect of CAuNPs. The enhancement factors revealed a concentration dependence of the enhancing effect at low concentration of rhodamine 6G. This dependency was due to a large capacity of hot-spots on CAuNPs, which were formed without agglomeration. The surface-enhancing behaviour in the film systems was similar to that in the dispersions, although the large CAuNPs had lower enhancing effect in the films, and the small CAuNPs and the spherical Au nanoparticles were more effective in their films. These results suggest that the CAuNPs have an advantage in ultrasensitive devices both in dispersions and films, compared to the agglomerate of spherical Au nanoparticles.

Coagulation and heterocoagulation interactions of components in aqueous dispersed systems microcrystalline cellulose–TiO2, microcrystalline cellulose–TiOSO4, and TiO2–TiOSO4

A procedure was developed for recovery and concentration of residual palladium(II) from a “lean” refining solution by extraction with 1Н-1,2,4-triazole derivatives. Palladium(II) is extracted quantitatively from 1 M hydrochloric acid solutions and under optimum conditions is selectively separated from platinum(IV) and rhodium(III).