Dissolution Behavior Research Articles

Atmospheric hydrochloric and nitric acid leaching of a limonite ore from the Wolo mine area, Southeast Sulawesi, Indonesia

The atmospheric acid leaching studies of a limonite ore sample from the Wolo mine area, Southeast Sulawesi, Indonesia, have been performed using hydrochloric acid (HCl) and nitric acid (HNO3). The objectives of these studies were to compare the leaching degree of metals (Ni, Co, Fe, and Al) and to analyze the dissolution behavior of minerals under different acid concentrations. Mineralogical characterization of the ore sample was conducted using optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction, whereas chemical composition was determined by X-ray fluorescence (XRF) spectrometry and atomic absorption spectroscopy (AAS), respectively. An atmospheric leaching test was done with the variables of acid concentration, leaching duration of 90 min, and leaching temperature of 100℃. Limonite ore samples contain goethite, gibbsite, talc, quartz, and lizardite. It was revealed that as much as 92.22% of Ni and 90.14% of Fe could be leached using 3 M HCl, whereas only 63.14% of Ni and 38.74% of Fe could be extracted from limonite ore using 3 M HNO3. The higher leaching degree of Fe in HCl indicates low selectivity with Ni, which might contaminate pregnant leach solution (PLS), leading to further complications in the purification process. Results of the leaching experiment show that goethite was more easily dissolved in HCl than in HNO3.

Intrinsic dissolution rate modeling for the pharmacopoeia apparatus rotating disk compared to flow channel method

For a solid understanding of drug characteristics, in vitro measurement of the intrinsic dissolution rate is important. Hydrodynamics are often emphasized as the decisive parameter influencing the dissolution. In this study, experiments and computational fluid dynamic (CFD) simulations showed that the mixing behavior in the rotating disc apparatus causes an inhomogeneous flow field and a systematic error in the calculation of the intrinsic dissolution rate. This error is affected by both the experimental time and the velocity. Due to the rotational movement around the tablet center, commonly utilized in pharmacopeia methods, a broad variance is present with regard to the impact of fluid velocity on individual particles of the specimen surface. As this is significantly reduced in the case of uniform overflow, the flow channel is recommended for investigating the dissolution behavior. It is shown that rotating disc measurements can be compared with flow channel measurements after adjusting the measured data for the rotating disc based on a proposed, representative Reynolds number and a suggested apparatus-dependent correction factor. Additionally, modeling the apparatus-independent intrinsic dissolution rate for different temperatures in the rotating disc apparatus is possible using the adapted Levich’s equation.

Asiatic acid cyclodextrin inclusion micro-cocrystal for insoluble drug delivery and acute lung injury therapy enhancement

BackgroundAcute lung injury (ALI) is a fatal respiratory disease caused by overreactive immune reactions (e.g., SARS-CoV-2 infection), with a high mortality rate. Its treatment is often compromised by inefficient drug delivery barriers and insufficient potency of the currently used drugs. Therefore, developing a highly effective lung-targeted drug delivery strategy is a pressing clinical need.ResultsIn this study, the micro-sized inclusion cocrystal of asiatic acid/γ-cyclodextrin (AA/γCD, with a stoichiometry molar ratio of 2:3 and a mean size of 1.8 μm) was prepared for ALI treatment. The dissolution behavior of the AA/γCD inclusion cocrystals followed a “spring-and-hover” model, which meaned that AA/γCD could dissolve from the cocrystal in an inclusion complex form, thereby promoting a significantly improved water solubility (nine times higher than free AA). This made the cyclodextrin-based inclusion cocrystals an effective solid form for enhanced drug absorption and delivery efficiency. The biodistribution experiments demonstrated AA/γCD accumulated predominantly in the lung (Cmax = 50 µg/g) after systemic administration due to the micron size-mediated passive targeting effect. The AA/γCD group showed an enhanced anti-inflammatory therapeutic effect, as evidenced by reduced levels of pro-inflammatory cytokines in the lung and bronchoalveolar lavage fluids (BALF). Histological examination confirmed that AA/γCD effectively inhibited inflammation reactions.ConclusionThe micro-sized inclusion cocrystals AA/γCD were successfully delivered into the lungs by pulmonary administration and had a significant therapeutic effect on ALI.Graphic abstract

Synthesis of shape-programmable elastomer for a bioresorbable, wireless nerve stimulator

Materials that have the ability to manipulate shapes in response to stimuli such as heat, light, humidity and magnetism offer a means for versatile, sophisticated functions in soft robotics or biomedical implants, while such a reactive transformation has certain drawbacks including high operating temperatures, inherent rigidity and biological hazard. Herein, we introduce biodegradable, self-adhesive, shape-transformable poly (L-lactide-co-ε-caprolactone) (BSS-PLCL) that can be triggered via thermal stimulation near physiological temperature (∼38 °C). Chemical inspections confirm the fundamental properties of the synthetic materials in diverse aspects, and study on mechanical and biochemical characteristics validates exceptional stretchability up to 800 % and tunable dissolution behaviors under biological conditions. The integration of the functional polymer with a bioresorbable electronic system highlights potential for a wide range of biomedical applications.

Dissolution behavior of chromite mineral impurities in raw materials of glass production using scanning electron microscopy-energy dispersive spectrometer, X-ray fluorescence spectroscopy and Raman spectroscopy methods

Silica sand is an essential raw material for glass production. The specification of silica sand for each type of glass is the most important point, such as chemical purity, grain size, grain shape, and their impurities. Some of the impurities in the sand can be eliminated by processing yet some cannot be avoided. This paper indicates that as an impurity in the sand, chromite minerals dissolve in glass. 0.200 mm and 0.250 mm grain size chromite minerals were observed grain size change at 1350 °C − 1400 °C − 1450 °C. With increasing in temperature, the rate of size change in the grain diameter increased. Because of the chemical composition of chromite mineral, with increasing temperature, first of all, aluminum and magnesium content start to dissolve in soda lime silicate glass. Then, chromium content transforms into chromium oxide. The transformation rate depends on the mineral composition as well as the temperature and the residence time in the furnace. This paper concerns the chemical composition of the chromite by scanning electron microscopy equipped with energy dispersive spectrometer, the compositions of the raw material analyzed with X-ray fluorescence spectroscopy, inductively coupled plasma optical emission spectrometer and chromite characteristics analyzed by Raman Spectroscopy methods.

Chemical Structure-Physicochemical Property Relationships of Copolymers Utilizable for Negative-Tone Photoimaging via Chemical Amplification.

We demonstrate an understanding of different physicochemical properties of copolymers induced by systematic changes in their structural parameters, i.e., the chemical structure of the comonomer unit, composition, molecular weight, and dispersity. The terpolymers were designed to be implemented in a chemically amplified resist (CAR) to form negative-tone patterns. With two basic repeating units of 4-hydroxystyrene and 2-ethyl-2-methacryloxyadamantane as monomers for conventional CARs, the pendant group of the third methacrylate comonomer was varied from aromatic, aliphatic lactone to lactone rings to modulate the interaction capability of the copolymer chains with n-butyl acetate, which is a negative-tone developer. Along with these structures, the monomer composition, molecular weight, and dispersity were also controlled. Physicochemical properties of the synthesized copolymers having controlled structures, i.e., dissolution behaviors and quantified Hansen solubility parameters, surface wetting characteristics, and surface roughness, which can be important properties affecting patterning capability in high-resolution lithography, were explored. Furthermore, the feasibility to use experimentally determined Hansen solubility parameters of the copolymers for the prediction of pattern formation using a coarse-grained model was assessed. Our comprehensive studies on the correlation of the structural parameters of the copolymers with final properties offer fundamental avenues to attain effective designs of the complex CAR system toward the lithographic process to achieve a sub-10 nm dimension, which is close to a single-chain dimension.

In Situ Observation of the Dissolution, Collision, and Aggregation Behavior of Nitride Inclusions in GH4169 Nickel-Based Superalloy

In Situ Observation of the Dissolution, Collision, and Aggregation Behavior of Nitride Inclusions in GH4169 Nickel-Based Superalloy

Dissolution Profiles of Oral Disintegrating Tablet with Taste Masking Granule Polymer Coating in Biorelevant Bicarbonate Buffer.

The current study aimed to explore the impact of buffer species on the dissolution behavior of orally disintegrating tablets (ODT) containing a basic polymer and its influence on bioequivalence (BE) prediction. Fexofenadine hydrochloride ODT formulations were used as the model formulations, Allegra® as the reference formulation, and generic formulations A and B as the test formulations. Allegra®, generic A, and generic B are ODT formulations that contain aminoalkyl methacrylate copolymers E (Eudragit® E, EUD-E), a basic polymer commonly used to mask the bitter taste of drugs. Both generic A and generic B have been known to be bioequivalent to Allegra®. The dissolution tests were conducted using a compendial paddle, with either bicarbonate (10 mM, pH 6.8) or phosphate buffer (25 mM, pH 6.8) as the dissolution media. A floating lid was employed to cover the surface of the bicarbonate buffer to prevent volatilization. Results indicated that in phosphate buffer, the dissolution profiles of Allegra and generic B significantly varied from that of generic A, whereas in the bicarbonate buffer, the dissolution profiles of Allegra, generic A, and generic B were comparable. These findings suggest that the use of bicarbonate buffer may offer a more precise prediction of human bioequivalence compared to phosphate buffer.

Wet peroxide oxidation process catalyzed by Cu/Al2O3: phenol degradation and Cu2+ dissolution behavior.

Catalytic wet peroxide oxidation (CWPO) has become an important deep oxidation technology for organics removal in wastewater treatments. Supported Cu-based catalysts belong to an important type of CWPO catalyst. In this paper, two Cu catalysts, namely, Cu/Al2O3-air and Cu/Al2O3-H2 were prepared and evaluated through catalytic degradation of phenol. It was found that Cu/Al2O3-H2 had an excellent catalytic performance (TOC removal rate reaching 96%) and less metal dissolution than the Cu/Al2O3-air case. Moreover, when the organic removal rate was promoted at a higher temperature, the metal dissolution amounts was decreased. Combined with hydroxyl radical quenching experiments, a catalytic oxidation mechanism was proposed to explain the above-mentioned interesting behaviors of the Cu/Al2O3-H2 catalyst for CWPO. The catalytic test results as well as the proposed mechanism can provide better guide for design and synthesis of good CWPO catalysts.

Electrochemical dissolution behavior of 07Cr16Ni6 alloy in sodium nitrate solution

07Cr16Ni6 alloy is a kind of martensitic-austenitic duplex stainless steel that is widely used in aviation and aerospace. Electrochemical machining (ECM) is an ideal manufacturing process for 07Cr16Ni6 alloy because of its high machining accuracy and good final surface quality. Studying the electrochemical dissolution behavior is pre-requisite and key to optimizing the ECM process; however, few studies have focused on the electrochemical dissolution behavior of 07Cr16Ni6 alloy. In this work, the corrosion behavior, passivation characteristics, efficiency curves, and material-removal process of 07Cr16Ni6 alloy in NaNO3 solution were comprehensively investigated. Based on the curves of potentiodynamic polarization and conductivity curve, it was found that both of them have significant passive and transpassive characteristics. The results of X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy indicated that the passive film was mainly composed of Fe3O4, α-Fe2O3, γ-Fe2O3, Cr2O3, NiO, SiO, and SiO2, and its structure was composed of a dense inner-layer film and a loose outer-layer film. A schematic model was proposed to characterize the interface structure between the 07Cr16Ni6 alloy, the passive film and electrolyte. ECM tests were performed at different current densities and for different corrosion times. The current-efficiency results indicate that the material-removal rate can be divided into three regions. The current efficiency first rises gently, then rises steeply once the current density exceeds 26 A cm−2; it finally remains stable at current densities greater than 45 A cm−2. The corrosion morphology exhibits loose, blocky bulges at low current density, while the surface exhibits lath-type martensite structures when the current density j > 15 A cm−2. The material-dissolution process of the 07Cr16Ni6 alloy in NaNO3 solution at 20 A cm−2 was presented. Finally, a model of dissolution was established to characterize the electrochemical dissolution of the 07Cr16Ni6 alloy in NaNO3 solution.

Dissolution behavior and improvement approach for gallium extraction from zinc refinery residues

Aiming at solving low Ga leaching efficiency during actual industrial production in Danxia Smelter, chemical composition, phases and morphologies of various zinc refinery residues were characterized using ICP−AES, XRD and SEM−EDS. Compared with the normal material, Ga was embedded in the jarosite phase from the special zinc refinery residue, causing difficulty in Ga leaching. During the oxidation pressure leaching, the dissolution behaviors of Ga, As and Fe presented similar variation tendency. Namely, a sufficient H2SO4 concentration and liquid-to-solid ratio promoted the dissolution of Ga, Fe and As, whereas higher reaction temperature and oxygen partial pressure weakened the leaching. Based on the results, leaching parameters were optimized for enhancing Ga recovery. Through weakening the 1st oxidation pressure leaching (by decreasing reaction temperature and total pressure to 90 °C and 0.2 MPa, respectively) and strengthening the 3rd atmospheric leaching (by increasing H2SO4 concentration and reaction temperature to 160 g/L and 85 °C, respectively), the leaching efficiency of Ga increased from 77.83% to 96.46%.

Simulation-Assisted Tool Design for Pulsed Electrochemical Machining of Magnetic Shape-Memory Alloys

Shape-memory alloys set high demands on the production technologies being used. During cutting, continuous heat input and mechanical stress have an undesirable influence on the shape-memory effect. Pulsed electrochemical machining (PECM), which is based on anodic dissolution, enables force-free machining without thermomechanical influence on the edge-zone properties of the workpiece. Depending on the desired geometry, the development of a customized PECM fixture is necessary. The design of the fixtures is often based on the experiences of the designers and manufacturers, which often results in an estimation of the functionally critical dimensions. For this reason, the study focuses on a methodical approach for evaluating crucial fixture dimensions using knowledge of the specific material dissolution behavior linked with a numerical simulation model. It has been shown that the shape-memory alloy NiMnGa has a non-linear dissolution behavior in sodium nitrate. A reduction of stray currents up to 20% resulting from a lateral gap between the cathode and electrical insulation was demonstrated using numerical simulation. The study shows that a low cathode shaping height has the strongest influence on precise processing. Varying the process parameters allowed for the lateral gap to be adjusted between 0.15 and 0.25 mm.

Studying the API Distribution of Controlled Release Formulations Produced via Continuous Twin-Screw Wet Granulation: Influence of Matrix Former, Filler and Process Parameters.

Hydroxypropyl methylcellulose (HPMC) is a preferred hydrophilic matrix former for controlled release formulations produced through continuous twin-screw wet granulation. However, a non-homogeneous API distribution over sieve fractions with underdosing in the fines fraction (<150 µm) was previously reported. This could result in content uniformity issues during downstream processing. Therefore, the current study investigated the root cause of the non-homogeneous theophylline distribution. The effect of process parameters (L/S-ratio and screw configuration) and formulation parameters (matrix former and filler type) on content uniformity was studied. Next, the influence of the formulation parameters on tableting and dissolution behavior was investigated. Altering the L/S-ratio or using a more aggressive screw configuration did not result in a homogeneous API distribution over the granule sieve fractions. Using microcrystalline cellulose (MCC) as filler improved the API distribution due to its similar behavior as HPMC. As excluding HPMC or including a hydrophobic matrix former (Kollidon SR) yielded granules with a homogeneous API distribution, HPMC was identified as the root cause of the non-homogeneous API distribution. This was linked to its fast hydration and swelling (irrespective of the HPMC grade) upon addition of the granulation liquid.

Impact of crystal polymorphism of rifaximin on dissolution behavior

IntroductionRifaximin is an intestinal antiseptic which has five (pseudo) polymorphs α, β, γ, δ and ε. These last (pseudo)polymorphs have different physicochemical properties. The objective of the study is to assess the impact of rifaximin polymorphism on its dissolution rate which could affect its bioavailability. Material and methodsThe analytical validation of dissolution assay method by UV–Visible spectrophotometry was carried out according to ICH Q2. The physicochemical characterization (solubility test, FTIR, DSC, XRD) was carried out on four active pharmaceutical ingredient (MP1, MP2, MP3, MP4). MP1 and MP2 were used by the manufacturer of generic brand 1 (G1) and MP3 and MP4 were used by the manufacturer of generic brand 2 (G2). The comparative in-vitro dissolution study was carried out on the leader brand (P), G1 and G2. ResultsThe four MPs were analyzed by XRD. The results of analysis showed that MP1 and MP4 were a mixture of α form and amorphous form. MP2 had an amorphous form and MP3 had a crystalline form β. The spectra of FTIR showed that the four MP had characteristics bands of rifaximin in the domain 4000-400 cm−1. The differences between the spectra of the four MPs were observed among the amorphous form (MP2), around the region 1800 to 1820 cm−1 which is attributed to the vibration of the CO group. An additional difference observed among the amorphous form (MP2) is around the region 1400 cm−1 which is attributed to the banding OH. The thermograms of MP1, MP2 and MP4 showed endothermic peaks which are probably attributed to the departure of water which indicate that MP1, MP2 and MP4 are pseudopolymoph (hydrate). For the four MPs, probably the melting points are interrupted by the phenomenon of phase transformations (Crystallization) which are reflected by exothermic peaks around 200°C–250 °C.Our results showed that the crystalline polymorphism of rifaximin influences its solubility. According to the results of the solubility test, the β crystal form of rifaximin (MP3) had the lowest solubility (3.47 μg/ml). MP2 had the highest solubility (8.35 μg/ml) and MP1 and MP4 had intermediate solubilities (5.47 μg/ml and 6.74 μg/ml). Comparative in vitro dissolution results showed that the dissolution profile of P was not similar to that of G1 and G2 (% dissolution (P)30min = 60%; % dissolution (G1) 30 min = 100% and % dissolution (G2) 30 min = 115%; f1(P versus G1) = 44; f1(P versus G2) = 61) in M1, while G1 and G2 had comparatively similar dissolution profiles (% dissolution (G1) 30 min = 100%; % dissolution (G1) 30 min = 110%; f1 (G1 versus G2) = 14) in M1. ConclusionThis study highlighted the impact of rifaximin polymorphism on its physico-chemical properties (crystal structure, thermal behavior, solubility) and on its dissolution behavior which could affect the rifaximin bioavailability.

Trace polymer coated clarithromycin spherulites: Formation mechanism, improvement in pharmaceutical properties and development of high-drug-loading direct compression tablets

Clarithromycin (CLA) is a high dose antibiotic drug exhibiting poor flowability and tabletability, making the tablet development challenging. This study aims to develop spherulitic CLA by introducing trace amount of polymer in crystallization solution. Its formation mechanism, physicochemical properties and potential for the direct compression (DC) tablets development were also investigated. Morphological analyses and the in situ observation on crystallization process revealed that the CLA spherulites are formed by fractal branching growth from both sides of the threadlike precursor fibers. 1H NMR analysis and nucleation time monitoring indicated that the existence of hydroxypropyl cellulose in solution slowed down the crystal nucleation and growth rate by forming hydrogen bonding interactions with CLA molecules, making the system maintain high supersaturation, providing high driving forces for CLA spherulitic growth. In comparison to commercial CLA, the CLA spherulites exhibit profoundly improved flowability, tabletability and dissolution behaviors. XPS, contact angle and Raman mapping analysis confirmed the presence of a thin HPC layer on the surfaces and interior of CLA spherulitic particles, resulting in increasing powder plasticity, interparticulate bonding strength and powder wettability, thus better tabletability and dissolution performances. The improved flowability and tabletability of CLA spherulites also enabled the successful development of DC tablet formulation with a high CLA loading (82.8 wt%) and similar dissolution profiles to reference listed drug. This study provides a novel solid form of CLA with superior manufacturability for further development.

Leaching of catalyst platinum from cured silicone elastomers: A preliminary study for comparing reagents

Addition curing systems involve two-part silicones which require the mixture of a silicone polymer with a catalyst to initiate the cure. Platinum is the most commonly used metal catalyst for addition curing of silicones by hydrosilylation which involves the crosslinking by the addition reaction of silicon hydride species to unsaturated bonds, mainly CC, but also CO or CN double bonds. After crosslinking of the polymers, the platinum catalyst cannot be recovered but remains in the silicone materials throughout the entire product life. In the end, platinum is disposed of together with the silicones and is thus lost to the value chain. The overall objective of this work was to develop a recycling process for the recovery of platinum from addition-cured silicone elastomers. In the first step, this was achieved by efficient digestion methods and by optimizing the leaching processes for exemplary commercial silicone elastomer products. Two different silicone materials were investigated, both of which were crosslinked with a platinum catalyst. The initial Pt content in the tested samples was 12.6 ± 0.2 mg/kg for a commercial silicone impression material and 6.3 ± 0.5 mg/kg for a silicone baking mold, measured by graphite furnace atomic absorption spectrometry (GF-AAS). Samples were first frozen with liquid nitrogen to improve brittleness and then crushed with a simple food processor to obtain a silicone granule. Various acid mixtures, mainly based on sulfuric acid, were investigated as digestion methods in order to extract platinum from the silicone network. These had different effects on the dissolution behavior of silicone samples and the amount of platinum extracted in each case. The amount of platinum leached from the filtrate of the digested samples in each case was measured by ICP-OES to evaluate the efficiency of different leaching mixtures. In addition, the dissolved platinum species present in the solutions was identified by UV/VIS as tetrachloridoplatinate(II) complex. The best platinum leaching results so far were obtained with two methods, both of which used a leaching mixture based on sulfuric acid and hexamethyldisiloxane (M2). In the presence of hydrochloric acid, 9.6 ± 1.6 mg platinum/kg was leached from the silicone impression material and 4.2 ± 0.8 mg platinum/kg from the silicone baking mold. With the additional use of aqua regia instead of hydrochloric acid, 10.4 ± 2.8 mg platinum/kg was extracted from the silicone impression material and 4.8 ± 1.0 mg platinum/kg was extracted from the silicone baking mold. These methods were replicated with n = 3. Using statistical evaluation methods (F-test, t-test, and confidence interval), no significant difference was found between these two best methods. Recovery of platinum(0) from leach mixtures has not yet been achieved due to high dilution and very low platinum concentration in samples and will be part of another study.

Investigating the influence of protein secondary structure on the dissolution behavior of β-lactoglobulin-based amorphous solid dispersions

Proteins acting as carriers in amorphous solid dispersions (ASDs) demonstrate a notable sensitivity to the spray drying process, potentially leading to changes in their conformation. The main aim of this study was to investigate the dissolution performance of ASDs based on proteins with different content of secondary structures, specifically β-sheet and α-helix structures. We prepared β-sheet-rich and α-helix-rich β-lactoglobulin (BLG), along with corresponding ASDs containing 10 wt% and 30 wt% drug loadings, through spray drying using celecoxib as the model drug. Circular dichroism and Fourier Transform Infrared Spectroscopy results revealed that even though changes in secondary structure were obtained in the spray-dried powders, the BLGs exhibited reversibility upon re-dissolving in phosphate buffer with varying pH levels. Both β-sheet-rich BLG and α-helix-rich BLG exhibited enhanced dissolution rates and higher solubility in the media with pH values far from the isoelectric point (pI) of BLG (pH 2, 7, 8, and 9) compared to the pH closer to the pI (pH 3, 4, 5, and 6). Notably, the release rate and solubility of the drug and BLG from both types of BLG-based ASDs at 10 wt% drug loading were largely dependent on the solubility of pure SD-BLGs. α-helix-rich BLG-ASDs consistently exhibited equivalent or superior performance to β-sheet-rich BLG-ASDs in terms of drug release rate and solubility, regardless of drug loading. Moreover, both types of BLG-based ASDs at 10 wt% drug loading exhibited faster release rates and higher solubility, for both the drug and BLG, compared to the ASDs at 30 wt% drug loading in pHs 2, 7, and 9 media.

Electrochemical dissolution behavior of stainless steels with different metallographic phases and its effects on micro electrochemical machining performance

To investigate the anodic dissolution of stainless steels with diverse metallographic phases and its impact on micro electrochemical machining (micro-ECM) performance, the electrochemical behavior of representative ferritic stainless steel (SUS430), martensite stainless steel (SUS440C), dual-phase stainless steel (2205 DSS), and austenite stainless steel (SUS316L) in neutral solutions were examined by analyzing potentiodynamic results and electrochemical impedance spectroscopy (EIS). The growth and chemical compositions of passive films on the stainless steels were evaluated using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). EIS results indicate that the passive film formed on SUS430 (ferritic phase) and SUS440C (martensite phase) in NaClO3 exhibited greater stability compared to that formed in NaNO3, which is attributed to the thicker passive film formed in NaClO3 and higher Fe2+/Fe3+ ratio as well as Cr2O3/Cr(OH)3 ratio. The SUS316L (austenite phase) exhibits almost the opposite behavior compared to the SUS430 and SUS 440C. The impact of the electrochemical behavior on the evolution of dissolution region and surface topography was discussed from the micro-ECM experimental results. The 2205 DSS exhibits a much higher corrosion resistance, but local corrosion zones were observed at the edges of microgrooves, leading to approximate material removal rate values compared to single-phase steels. The metallographic phases influence the composition, structure, and density of the passive films, and determine the ECM performance. This study demonstrates the relationships between the MRRs and the metallographic phases of stainless steel, which provides a feasible idea for optimizing the matches of the electrolyte composition and stainless steel workpiece.

Influence of preparation method and choice of phospholipid on co-amorphization, physical stability, and dissolution behavior of equimolar indomethacin-phospholipid systems – A case study

This case study aimed to evaluate the feasibility of forming equimolar co-amorphous drug-phospholipid systems by different preparation methods. Indomethacin (IND) was chosen as a model drug and combined with three phospholipids of natural origin (soybean phosphatidylcholine (SPC), hydrogenated phosphatidylcholine (HPC), and mono-acyl phosphatidylcholine (MAPC), at equimolar ratios. The systems were prepared by mechano-chemical activation-based, melt-based, and solvent-based preparation methods, i.e., ball milling (BM), quench cooling (QC), and solvent evaporation (SE), respectively. X-ray powder diffraction (XRPD), polarized light microscopy (PLM), and differential scanning calorimetry (DSC) were used to determine the solid state form of the prepared IND-phospholipid systems. The long-term physical stability of the co-amorphous systems and the amorphous drug alone were investigated under dry conditions at room temperature. The dissolution behavior of the formed co-amorphous drug-phospholipid systems was also studied. Our findings indicate that SE-prepared co-amorphous drug-phospholipid systems can be successfully prepared across all systems, whereas the QC method could only form co-amorphous drug-phospholipid systems for IND-SPC and IND-MAPC. In contrast, the BM method failed to produce co-amorphous drug-phospholipid systems, but the drug alone could be fully amorphized. The physical stability of SE-prepared co-amorphous drug-phospholipid systems was significantly prolonged under dry conditions (172–236 days) compared to pure amorphous IND (8–15 days) and all other systems (22–38 days). Furthermore, the co-amorphous drug-phospholipid systems formed by the SE method demonstrated improved dissolution behavior in comparison to crystalline IND, amorphous IND, and physical mixtures of IND and phospholipids. However, the phospholipids did not inhibit precipitation in the formed supersaturated IND solutions.

Poly(vinylpyridine-co-vinylpyridine N-oxide) Excipients Mediate Rapid Dissolution and Sustained Supersaturation of Posaconazole Amorphous Solid Dispersions.

The chemical structure of excipients molecularly mixed in an amorphous solid dispersion (ASD) has a significant impact on properties of the ASD including dissolution behavior, physical stability, and bioavailability. Polymers used in ASDs require a balance between hydrophobic and hydrophilic functionalities to ensure rapid dissolution of the amorphous dispersion as well as sustained supersaturation of the drug in solution. This work demonstrates the use of postpolymerization functionalization of poly(vinylpyridine) excipients to elucidate the impact of polymer properties on the dissolution behavior of amorphous dispersions containing posaconazole. It was found that N-oxidation of pyridine functionalities increased the solubility of poly(vinylpyridine) derivatives in neutral aqueous conditions and allowed for nanoparticle formation which supplied posaconazole into solution at concentrations exceeding those achieved by more conventional excipients such as hydroxypropyl methylcellulose acetate succinate (HPMCAS) or Eudragit E PO. By leveraging these functional modifications of the parent poly(vinylpyridine) excipient to increase polymer hydrophilicity and minimize the effect of polymer on pH, a new polymeric excipient was optimized for rapid dissolution and supersaturation maintenance for a model compound.