Higher Dissolution Rate Research Articles

Determination of the maximum dissolution rates of the Belgian reference glasses at very alkaline pH and 30 °C

To assess the chemical durability of the Belgian reference glasses SON68, SM513, and SM539 under hyper-alkaline conditions, maximum glass dissolution rates were measured at 30 °C and pH 13.5 by performing Single-Pass Flow-Through tests with a KOH solution and a synthetic young cementitious water containing Ca (YCWCa). In both leachants, the highest dissolution rate was determined for the Al-rich glass SM539, while similar rates were found for SM513 and SON68 glasses, whose compositions are comparable. For all glasses, the dissolution rates in YCWCa were lower than in KOH due to the presence of Ca, which leads to the formation of a slightly protective calcium silicate layer. The dissolution rates in YCWCa were similar to those determined from glass monolith mass losses in static tests carried out at 30 °C in YCWCa in the presence of hardened Ordinary Portland Cement paste powder with a cement-to-glass ratio of 1.Graphical abstract

Effects of Y substituting Gd on the microstructure evolution, mechanical properties and dissolution behaviors in the Mg-Gd-Ni alloys used as fracturing plugging tools

In this work, the effects of substituting 3 wt% Gd with 3 wt% Y on the microstructure, mechanical properties, and corrosion behaviors in the Mg-Gd-Ni alloys were investigated. By substituting Gd with Y, the area fraction of bulk-shaped long-period stacking ordered phases (LPSO) increases, while one of eutectic Mg2Ni phase decreases slightly. Moreover, it also promotes the precipitations of lamellar LPSO phase and nanoscale stacking faults (SFs). The tensile tests showed that the addition of Y increased the yield strength by about 40 MPa, mainly due to the strengthening of the kink deformation of the bulk shaped LPSO phase, the hindering effect of the lamellar LPSO and SF on dislocation movement, and the strengthening caused by grain refinement. As a result, the Mg-5Gd-3Y–5Ni (MGYN) alloy exhibits excellent mechanical properties with tensile yield strength (TYS) of 288 MPa, ultimate tensile strength (UTS) of 364 MPa, and elongation (EL) of 8.3 %. Moreover, although the fraction of Mg2Ni phase with high electrochemical potential is decreased, the reduction in dissolution rate is not significant because the discontinuous distribution of lamellar LPSO in the grains intensifies the galvanic corrosion by increasing the proportion of cathode phase. As a result, the coexistence of Mg2Ni and LPSO phases can observably improve the dissolution rate. Finally, the highest dissolution rate (234.56 mg cm−2 h−1 in 3 wt% KCl solution at 93 °C) reported so far for the dissoluble magnesium alloys can be attained for MGYN alloy in this study. This work provides an economical material selection with high dissolution rate and sufficient strength for the fabrication of the fracturing plugging tools.

Muddy sediments are an important potential source of silicon in coastal and continental margin zones

The dissolution of silicate minerals on the seafloor releases an important amount of dissolved silicon (dSi), which is necessary for maintaining high diatom production in Coastal and Continental Margin Zones (CCMZs). However, the dissolution of silicate minerals along the continental shelves is variable, which hinders our understanding of the marine Si cycle on both a regional and global scale. To understand the discrepancy of silicon (Si) released in different sediment matrices and its potential controlling factors, we investigated surface sediments of typical CCMZs of the Chinese marginal Seas using a continuous alkaline extraction technique, grain size and chemical (carbon and total nitrogen) analysis as well as a qualitative measurement of clay mineral composition by X-ray diffraction. The results showed that the amount of Si and aluminum (Al) leached from muddy sediments were 2 times greater than those released from sandy sediments. High dissolution rates (> 0.20 mg-SiO2 g−1 min−1) of silicate minerals are caused by a large sediment-specific surface area. Further, our data showed that biogenic silica (bSi) with high Al content (Si:Al < 40) has low reactivity and that the source of Al incorporated in bSi is silicate minerals undergoing dissolution. We show that although the dissolution of silicate minerals is less active than that of bSi, it still potentially releases more bio-available Si and Al to seawater due to its dominant presence on the seafloor (70.3% − 99.0%wt). This study highlights silicate minerals as an important potential marine Si source and emphasizes the need for a better understanding of the roles of silicate minerals in the Si cycle of marginal seas in future studies.

Evaluation of toxicity using zebrafish embryo model and preparation of enteric-coated pellets containing Panax notoginseng saponins

Panax notoginseng saponins (PNS) extracted from the root of Panax notoginseng (Burk.) F. H. Chen are the main biologically active substances. However, PNS have low permeability and degradation in the acid gastric environment, leading to their limited bioavailability. This study aimed to determine the acute toxicity of PNS in zebrafish larvae and prepare enteric-coated pellets of PNS to enhance their permeability and stability. The survival proportion, the morphological abnormalities, and the heartbeat of zebrafish embryos were performed at treated doses of PNS ranging from 0.01 to 50 μg/ml. Administration of PNS at doses greater than 10 μg/ml may result significantly in morphological alterations such as pericardial edema and curved tail. The core pellets containing PNS, polyethylene glycols, and absorption enhancers were fabricated by the dripping method. Then, the dripping pellets were coated using Eudragit L100 as an enteric coating polymer. The characterizations of core pellets and enteric-coated pellets were evaluated. The produced dripping pellets showed advantageous features, such as ease of preparation, excellent uniformity, notable friability, high dissolution rate, and good stability. In addition, absorption enhancers were successfully incorporated into the core pellets to improve the permeability of PNS. Differential scanning calorimetry, X-ray powder diffraction, and Fourier-transform infrared spectroscopy profiles revealed that the drug was maintained in an amorphous state and did not interact with the excipients during the pellet preparation process. Histological evaluation showed that dripping pellets caused a minor effect on the surface of the jejunal mucosa. The enteric-coated pellets displayed smooth surface morphology, desirable sphericity, good flowability, uniform content, and stability in an acidic pH 1.2 environment and rapid drug release in a pH 6.8 buffer solution. Based on the findings, the enteric-coated pellets may improve the absorption and stability of PNS.

Design and Characterization of a Melt Electrostatic Precipitator for Advanced Drug Formulations

Electrostatic precipitators (ESP) are especially known for the efficient separation of micron and submicron particles from aerosols. Wet electrostatic precipitators are particularly suitable for highly resistive materials. Using these, particles can be directly transferred into a liquid for further processing or safer handling, which is advantageous for either hazardous or valuable materials. In this work, a wet ESP, which enables the separation of highly resistive particles into a heated liquid, was designed and investigated. To do this, spray-dried drug particles were embedded in a molten sugar alcohol to enhance the drug dissolution rate. After cooling, the solidified product showed advantageous properties such as a high drug dissolution rate and easy handling for further processing. For the design of the wet ESP, different discharge electrode configurations were tested. A wall film served as the collection electrode, which was generated by a specially designed distributer die. A laminar flow regime was achieved with a homogeneous film serving as the collection electrode, which is particularly important for a high separation efficiency. A prototype was designed and constructed in this respect. The particle separation into hot liquids or onto hot surfaces is challenging due to thermal effects in ESPs. The influence of thermophoresis and drag force on the particle transport was investigated, and optimum operation parameters were found for the present ESP. A broad field of applications can be covered with the presented device, where particles are embedded in even hot liquids to form liquid suspensions or, as it is presented here, solid dispersions. The dissolution of the drug-containing solid dispersion was studied in vitro. A remarkably faster drug dissolution was observed from the solid dispersion, as compared to a powder mixture of the drug and xylitol.

Research on organic polyacid system suitable for water injection wells in low permeability reservoirs

Abstract Currently, the pollution and clogging problems of injection wells in low-permeability reservoirs are becoming more and more serious, leading to a series of issues, such as the decline of fluid production in wells and the increase of pressure in injection wells. To cope with these challenges, SY organic polyacid solution was developed in this paper and its dissolution efficiency was thoroughly investigated. The experimental results show that SY organic polyacid solution has a high dissolution rate of 88.7%, which exhibits excellent scale dissolution effect, and the solvent's dissolution has a good slow-release performance to ensure the long-lasting action time. At the same time, the corrosion rate of the solvent on the N80 steel sheet is only 0.6291 g/m²-h, much lower than the industry standard, which effectively protects the safety of the construction pipeline and production column. In addition, the dissolution rate of SY organic polyacid on clay reaches 10.14% in five minutes, indicating that it prevents the ground collapse caused by excessive dissolution of clay and has good profound penetration ability. In summary, using SY organic polyacid solution can effectively solve multiple problems such as reservoir mud, inorganic scale, organic scale and water injection fouling oil, which provides an effective solution for the contamination and clogging of water injection wells in low permeability reservoirs.

Design of a multi-functional ionic liquid for electron stripping and coordinated complexation and its noble metal dissolution mechanism

A task-specific ionic liquid ([dibmim]Cl) showing a high dissolution rate for noble metals was reported herein, and the dissolution mechanism of Pd as representative of noble metals, was deduced from a series of characterization. The electron stripping and dissolution mechanism process was further verified using DFT calculation.

Effects of N/Si ratio on mechanical properties of amorphous silicon nitride coating

The utilization of silicon nitride coatings has been proposed as an effective method to enhance wear resistance and mitigate the release of metallic ions from biomedical implants. However, the relatively high dissolution rate of low-density coatings remains an obstacle to their implementation. Here, chemical vapour deposition techniques may have advantages over the typically used physical vapour deposition (PVD) methods. Therefore, in this study, silicon nitride coatings were obtained by low-pressure chemical vapor deposition (LPCVD). Since the nitrogen-to-silicon (N/Si) ratio and deposition temperature have been reported as major factors affecting the performance of the coatings, the effects of ammonia (NH3) to dichlorosilane (SiH2Cl2) flow ratio and deposition temperature were systemically investigated in the form of microstructure, mechanical and tribological properties of the coatings. The results revealed that the coatings exhibited a dense structure. As the ammonia flow ratio increased, the surface became smoother, and the hardness and elastic modulus increased and reached the maximum at a flow ratio of 4, giving a hardness of around 27 GPa and an elastic modulus of 290 GPa, respectively. The higher mechanical properties of the coatings deposited at a flow ratio of 4 are attributed to the stronger covalent Si-N bonding, as confirmed by XPS results. However, the coatings deposited at a flow ratio of 2 exhibited the lowest wear rate, at 9.5 10−7 mm3 Nm−1, around one-third of the value of the coatings deposited at a flow ratio of 6, likely due to the high silicon content of these coatings. Increasing the temperature resulted in an increased deposition rate, higher hardness and elastic modulus as well as a lower wear rate, likely due to incomplete reactions at lower temperatures. The generally high hardness and low wear rate indicate that the coatings deposited by LPCVD are promising for application in spinal implants.

Preparation, properties and in vitro osteogensis of self-reinforcing injectable hydrogel

As an attractive biomaterial for bone reconstruction, injectable biomaterials have many prominent characteristics such as good biocompatibility and bone-filling ability. However, there are weak as load-bearing scaffolds. In this study, polyvinyl alcohol (PVA) and bioactive glass (BAG) were interpenetrated into sodium alginate (SA) network to obtain self-enhanced injectable hydrogel. The optimum ratio of PVA/SA/BAG hydrogel was determined based on injectability, gelation time and chemical characterization. Results showed that the selected ratio had the shortest gelation time of 3.5min, and the hydrogel had a rough surface and good coagulation property. The hydrogel was capable of carrying 1kg of weight by mineralization for 14 d The compressive strength, compressive modulus, and fracture energy of the hydrogel reached 0.12MPa, 0.376MPa and 17.750kJ m−2, respectively. Meanwhile, the hydrogel had high moisture content and dissolution rate, and it was sensitive to temperature and ionic strength. Hydroxyapatite was generated on the hydrogel surface, and the hydrogel pores increased, and the pore size enlarged. The biocompatibility of PVA/SA/BAG hydrogel was analyzed using hemolysis and cytotoxicity assays. Results revealed its good biocompatibility with low hemolysis rate and no cytotoxicity to MC3T3-E1 cells. The hydrogel was also found to promote the differentiation of MC3T3-E1 cells with significantly increased in ALP activity and expression of relevant differentiation factors. In vitro mineralization assay showed an increase in calcium nodules and calcification area, indicating the ability of hydrogel to promote mineralization MC3T3-E1 cells. These findings indicated that PVA/SA/BAG hydrogel had potential uses in the field of irregular bone-defect repair due to its injectability, cytocompatibility, and tailorable functionality.

Experimental investigation of multiple industrial wastes for carbon dioxide removal strategies

Industrial solid waste by-products are being increasingly employed for geochemical carbon dioxide removal (CDR) strategies due to their fine grain size, accessibility, and large annual production tonnages. Here, a range of such by-products has been tested experimentally for their reactivities with CO2 and water. Sample solutions were monitored for 100 h for changes in chemistry, and solid samples were characterised pre- and post-experiment. Samples rich in Ca- and Mg-bearing minerals, such as dunite, kimberlite, and ilmenite mine tailings, as well as marble quarry cuttings, were key cation sources. Ni sulphide, fluorite and borax tailings, coal-fired power plant fly ashes, and red mud samples showed high dissolution rates. The highest reaction rates were often observed during the initial few hours, and compared well to rates determined for rocks typically targeted for CDR purposes, such as basalt and gabbro. Several samples also showed secondary carbonate precipitation, suggesting opportunities for the development of single-step CDR technologies. Overall, the results of this study indicate that several industrial by-products can provide sufficient cations at favourable dissolution rates for geochemical CDR purposes. Any on-site or near-site conditions for reaction acceleration such as heat, concentrated CO2 or microbes, could further increase favourability for geochemical CDR opportunities.

Coupled fluid flow, solute transport and dissolution processes in discrete fracture networks: An advanced Discontinuous Galerkin model

Modeling dissolution processes in discrete fracture networks (DFNs) is a challenging task. Challenges are related to the highly nonlinear coupling between flow, mass transport, and reactive processes associated with fracture aperture evolution by dissolution. Further, advection-dominated transport due to fast fluid flow in fractures renders the problem more complex from a computational point of view, as traditional numerical methods may introduce unphysical oscillations or excessive numerical diffusion. The Discontinuous Galerkin (DG) method is known to be suitable for the simulation of advection-dominated transport. In this work, an advanced DG model is developed to model transport with dissolution in DFNs. We propose an upwind formulation to deal with the upstream concentration at the intersection of several fractures. The upstream concentration at an intersection node is calculated based on the average nodal concentrations of all the fractures having an inflow at that node, weighted by the volumetric fluxes of these fractures. The dispersion term is discretized with the Mixed Finite Element (MFE) method, which ensures the continuity of the dispersive flux at the intersection of fractures with different apertures. The obtained nonlinear coupled flow-transport-dissolution equations are discretized in time with a high-order scheme via the method of lines (MOL). Numerical examples and comparisons with standard finite element (FE) and finite volume (FV) solutions are performed to investigate the correctness and efficiency of the developed model. Results show that the new DG-DFN model avoids unphysical oscillations encountered with the standard FE method and strongly reduces the numerical diffusion observed with the upwind FV scheme. The DG-DFN model is then used to investigate the effect of the dissolution rate on the flow, transport, and aperture evolution processes for a single fracture and for a DFN. A quasi-linear evolution of the fracture aperture is observed for low dissolution rates. For high dissolution rates, a funnel-shaped enlargement is observed with a significant widening for the fractures near the inlet and minor effects for those away from the injection location.

Emerging Applications of Hydroxypropyl Methylcellulose Acetate Succinate: Different Aspects in Drug Delivery and Its Commercial Potential.

Hydroxypropyl methylcellulose acetate succinate (HPMCAS) has multi-disciplinary applications spanning across the development of drug delivery systems, in 3D printing, and in tissue engineering, etc. HPMCAS helps in maintaining the drug in a super-saturated condition by inhibiting its precipitation, thereby increasing the rate and extent of dissolution in the aqueous media. HPMCAS has several distinctive characteristics, such as being amphiphilic in nature, having an ionization pH, and a succinyl and acetyl substitution ratio, all of which are beneficial while developing formulations. This review provides insights regarding the various types of formulations being developed using HPMCAS, including amorphous solid dispersion (ASD), amorphous nanoparticles, dry coating, and 3D printing, along with their applicability in drug delivery and biomedical fields. Furthermore, HPMCAS, compared with other carbohydrate polymers, shows several benefits in drug delivery, including proficiency in imparting stable ASD with a high dissolution rate, being easily processable, and enhancing bioavailability. The various commercially available formulations, regulatory considerations, and key patents containing the HPMCAS have been discussed in this review.

Preformulation study for the selection of a suitable polymer for the development of ellagic acid-based solid dispersion using hot-melt extrusion

Ellagic acid is one of the most studied polyphenolic compounds due to its numerous promising therapeutic properties. However, this therapeutic potential remains difficult to exploit owing to its low solubility and low permeability, resulting in low oral bioavailability. In order to allow an effective therapeutic application of EA, it is therefore necessary to develop strategies that sufficiently enhance its solubility, dissolution rate and bioavailability. For this purpose, solid dispersions based on pre-selected polymers such as Eudragit® EPO, Soluplus® and Kollidon® VA 64, with 5% w/w ellagic acid loading were prepared by hot extrusion and characterized by X-ray diffraction, FTIR spectroscopy and in vitro dissolution tests in order to select the most suitable polymer for future investigations. The results showed that Eudragit® EPO was the most promising polymer for ellagic acid solid dispersions development because its extrudates allowed to obtain a solution supersaturated in ellagic acid that was stable for at least 90 min. Moreover, the resulting apparent solubility was 20 times higher than the actual solubility of ellagic acid. The extrudates also showed a high dissolution rate of ellagic acid (96.25% in 15 min), compared to the corresponding physical mixture (6.52% in 15 min) or the pure drug (1.56% in 15 min). Furthermore, increasing the loading rate of ellagic acid up to 12% in extrudates based on this polymer did not negatively influence its release profile through dissolution tests.

A Comparative Study of the Biodurability and Persistence of Gold, Silver and Titanium Dioxide Nanoparticles Using the Continuous Flow through System.

The potential for nanoparticles to cause harm to human health and the environment is correlated with their biodurability in the human body and persistence in the environment. Dissolution testing serves to predict biodurability and nanoparticle environmental persistence. In this study, dissolution testing using the continuous flow through system was used to investigate the biodurability and persistence of gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO2 NPs) in five different simulated biological fluids and two synthetic environmental media to predict their behaviour in real life situations. This study examined the physicochemical properties and agglomeration state of gold, silver and titanium dioxide nanoparticles before and after dissolution tests using three different techniques (UV-vis, XRD and TEM). The UV-vis spectra revealed that all three nanoparticles shifted to higher wavelengths after being exposed to simulated fluids. The titanium powder was found to be mixed with both rutile and anatase, according to XRD examination. The average diameter of gold nanoparticles was 14 nm, silver nanoparticles were 10 nm and titanium dioxide nanoparticles were 25 nm, according to TEM images. The gold and silver nanoparticles were observed to be spherical, but the titanium dioxide nanoparticles were irregular in shape, with some being spherical. The level of dissolved nanoparticles in simulated acidic media was higher in magnitude compared to that dissolved in simulated alkaline media. The results obtained via the continuous flow through dissolution system also displayed very significant dissolution rates. For TiO2 NPs the calculated half-times were in the range of 13-14 days, followed by AuNPs ranging between 4-12 days, significantly longer if compared to the half-times of AgNPs ranging between 2-7 days. AuNPs and TiO2 NPs were characterized by low dissolution rates therefore are expected to be (bio)durable in physiological surroundings and persistent in the environment thus, they might impose long-term effects on humans and the environment. In contrast, AgNPs have high dissolution rates and not (bio)durable and hence may cause short-term effects. The results suggest a hierarchy of biodurability and persistence of TiO2 NPs > AuNPs > AgNPs. It is recommended that nanoparticle product developers should follow the test guidelines stipulated by the OECD to ensure product safety for use before it is taken to the market.

球状多孔質β型リン酸三カルシウム顆粒を用いたセメントの作製と評価

Calcium phosphate cements (CPCs) with macropores and micropores for high bone regeneration ability are desired. CPCs with macropores and micropores which were prepared by combining porous granules have been reported. In this study, the cement system composed of β-tricalcium phosphate (β-TCP) granules and phosphoric acid solution was selected, and the effects of the characteristics of granules on the microstructures and properties of the cements were examined. The spherical porous β-TCP granules with high porosity and irregular porous β-TCP granules with low porosity were prepared, and they were mixed with a phosphoric acid solution. When the spherical porous granules with high porosity were used, the granules were packed uniformly in the cement, and the size distribution of the macropores formed among the granules was narrower than that of the cement prepared using the irregular porous β-TCP granules with low porosity. The cement with high porosity can be obtained from the spherical porous granules with high porosity. The cement prepared using the spherical granules with high porosity showed lower compressive strength and higher dissolution rate than the cement prepared using irregular granules with low porosity.

Optimization of a solidified micelle formulation for enhanced oral bioavailability of atorvastatin calcium using statistical experimental design

To enhance the oral bioavailability of atorvastatin calcium (ATV), a novel solidified micelle (S-micelle) was developed. Two surfactants, Gelucire 48/16 (G48) and Tween 20 (T20), were employed for micelle formation, and two solid carriers (SC), Florite PS-10 (FLO) and Vivapur 105 (VP105), were selected as solid carriers. The S-micelle was optimized using a Box-Behnken design with three independent variables, including G48:T20 (X1 , 1.8:1), SC:G48 + T20 (X2 , 0.65:1), and FLO:VP105 (X3 , 1.4:0.6), resulting in a droplet size (Y1 ) of 198.4 nm, dissolution efficiency at 15 min in the pH 1.2 medium (Y2 ) of 47.6%, Carr’s index (Y3 ) of 16.9, and total quantity (Y4 ) of 562.5 mg. The optimized S-micelle resulted in good correlation showing percentage prediction values less than 10%. The optimized S-micelle formed a nanosized dispersion in the aqueous phase, with a higher dissolution rate than raw ATV and crushed Lipitor®. The optimized S-micelle improved the relative bioavailability of oral ATV (25 mg equivalent/kg) in rats by approximately 509 and 271% compared to raw ATV and crushed Lipitor®, respectively. In conclusion, the optimized S-micelle possesses great potential for the development of solidified formulations for improved oral absorption of poorly water-soluble drugs.

Development of Clinically Optimized Sitagliptin and Dapagliflozin Complex Tablets: Pre-Formulation, Formulation, and Human Bioequivalence Studies.

The purpose of this study is to derive an optimal drug release formulation with human clinical bioequivalence in developing a sitagliptin phosphate monohydrate-dapagliflozin propanediol hydrate fixed-dose combination (FDC) tablet as a treatment for type 2 diabetes mellitus. As a treatment for type 2 diabetes mellitus, the combined prescription of dipeptidyl peptidase-4 (DPP-4) inhibitors and sodium-glucose cotransporter-2 (SGLT-2) inhibitors is common. Therefore, this study simplified the number of individual drugs taken and improved drug compliance by developing FDC tablets containing sitagliptin phosphate monohydrate as a DPP-4 inhibitor and dapagliflozin propanediol hydrate as an SGLT-2 inhibitor. To derive the optimal dosage form, we prepared single-layer tablets, double-layer tablets, and dry-coated tablets and evaluated the drug control release ability, tableting manufacturability, quality, and stability. Single-layer tablets caused problems with stability and drug dissolution patterns. When the dissolution test was performed on the dry-coated tablets, a corning effect occurred, and the core tablet did not completely disintegrate. However, in the quality evaluation of the double-layer tablets, the hardness was 12-14 kilopond, the friability was 0.2%, and the disintegration was within 3 min. In addition, the stability test revealed that the double-layer tablet was stable for 9 months under room temperature storage conditions and 6 months under accelerated storage conditions. In the drug release test, only the FDC double-layer tablet showed the optimal drug release pattern that satisfied each drug release rate. In addition, the FDC double-layer tablet showed a high dissolution rate of over 80% in the form of immediate-release tablets within 30 min in a pH 6.8 dissolution solution. In the human clinical trial, we co-administered a single dose of a sitagliptin phosphate monohydrate-dapagliflozin propanediol hydrate FDC double-layered tablet and the reference drug (Forxiga®, Januvia®) in healthy adult volunteers. This study showed clinically equivalent results in the stability and pharmacodynamic characteristics between the two groups.

Development of Delayed-Release Matrix Tablets Comprising Solid Dispersion of Mefenamic Acid

Mefenamic acid (MA), a member of nonselective nonsteroidal anti-inflammatory drugs (NSAIDs), has been widely use to relief pain and inflammation. Its medical uses are limited by poor aqueous solubility resulting in low bioavailability and gastric irritation. The aim of this study was to develop a mefenamic acid delayed-release matrix tablet formulation using solid dispersion (SD). Delayed-release drug delivery systems were designed to retard drug release in upper gastrointestinal tract avoiding gastrointestinal (GI) adverse reactions. SDs of MA were successfully prepared by solvent evaporation method employing methanol as a solvent. SDs incorporated surfactant and super disintegrant gave much higher rates of dissolution than SDs with combined carriers (PEG and surfactant), SD containing PEG and pure drug, respectively. The optimal SD containing MA:PEG4000:poloxamer188:crospovidone in the ratio 1:8:1:3 exhibited higher amount of drug release up to 8-fold compared with pure MA. FTIR and DSC were performed to identify the physicochemical interaction between drug and polymers. The resulting data justified that no change in the chemical structure of MA and the crystalline MA transformed into the amorphous state after preparation. The formulation F4 delayed-release tablet comprising SD of MA dissolved less than 4 % in artificial gastric fluid in the initial 2 h and released more than 95 % at 3 h in the artificial intestinal fluid. Accordingly, formulation F4 containing polyethylene oxide as a time-controlled matrix-forming polymer was a promising delayed-release solid dispersion system of MA. HIGHLIGHTS The present study demonstrated a mefenamic acid delayed-release matrix tablet formulation using solid dispersion (SD) The optimal SD of mefenamic acid exhibited higher amount of drug release (8-fold) compared with that of the pure drug The tablet formulation F4 containing polyethylene oxide is capable of releasing mefenamic acid in a typical delayed-release profile GRAPHICAL ABSTRACT

Micro and nanobubbles technologies as a new horizon for CO2-EOR and CO2 geological storage techniques: A review

CO2 capture, utilization, and storage technology are one of the most effective methods to reduce CO2. Although this technology has been relatively mature, the main problems limiting the large-scale application are the security of geological storage. The advantage of micro and nanobubbles is widely acknowledged due to their size and stability. Micro and nanobubbles are tiny gas-liquid dispersion systems with unique physical characteristics. The important features of micro and nanobubbles include their excellent stability, high internal pressure, extremely large surface-to-volume ratio, and high gas dissolution rate, which lead to promising applications in various fields. This review discussed the studies conducted in the areas of micro and nanobubbles with a special emphasis on CO2-EOR and CO2 geological storage. The micro and nanobubbles classifications and their composition were briefly introduced. The preparation methods of micro and nanobubbles and the main factors affecting their properties were investigated in detail. The characterization parameters with state- of – the art measuring and analysis techniques of microbubble and nanobubble technologies were summarized. Furthermore, the major applications in CO2-EOR and CO2 geological storage were discussed. Base on this review, various potential areas,and gaps for MNB research in CO2– EOR and CO2 geological storage fields are identified for further investigations.

Fracture Intensity Impacts on Reaction Front Propagation and Mineral Weathering in Three‐Dimensional Fractured Media

AbstractStudying reaction front propagation in heterogeneous natural settings is challenging, but numerical simulations can provide insight into the varying spatial and temporal scales of reaction front propagation. Here, the impact of increasing fracture intensity on mineral dissolution rates, and the extent of reaction front propagation is investigated using reactive transport simulations in upscaled discrete fracture network domains with varied fracture intensity. Domain‐averaged dissolution rates vary less than 0.5 log units regardless of the fracture intensity, but the spatial distribution of reactions is controlled by the location and number of dead‐end fractures and the number of connected flowpaths through the domain. Higher fracture intensities lead to more weathering in the domain because of more available mineral for water‐rock interactions. We find that reaction fronts propagate through the primary flowpaths in the first 10,000 years of the simulation for a 10‐m length domain, then propagate into secondary flowpaths and dead‐end fractures between 10,000 and 100,000 years, and finally into the matrix over timescales of hundreds of thousands of years. The domain‐averaged reaction rates decrease through time corresponding to a transition from dissolution in advection‐dominated, fast‐flowing pathways, to dissolution in transport‐limited zones of disconnected fractures and matrix. Matrix dissolution, or dissolution under transport‐limited conditions, is the dominant process at late times in these simulations. The results of these simulations recreate the observed paradox found in nature where highly fractured hillslopes tend to be more weathered but have slower weathering rates, while hillslopes with fewer fractures, are less weathered but have higher dissolution rates.