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About 10,000 papers for “Amorphous solid”

Amorphous Solid

William M. Irvine · Encyclopedia of Astrobiology · 2011

Cited by 0

Amorphous Solid

William M. Irvine · Encyclopedia of Astrobiology · 2023

Cited by 0

Amorphous solid water

Physics Bulletin · 1975

Water may be one of the most common substances, but its properties are by no means fully understood. Two studies published recently on the amorphous solid state of water may help to throw some light on the matter, and could provide valuable clues to the structure of the liquid.

Cited by 0

Amorphous solid carbon dioxide

Michael Falk · The Journal of Chemical Physics · 1987

Carbon dioxide gas condensed at 10 K was found to form amorphous solid films whose infrared spectra differ substantially from those of crystalline CO2. With the help of a sample of 13C-enriched CO2, the fundamental absorption bands of different isotopic species of CO2 in the spectra of the amorphous solid, crystalline solid, and of CO2 dispersed in solid nitrogen matrix were analyzed. Some conclusions regarding the structure of the amorphous solid are derived from the spectra.

Cited by 84

Amorphous Solid Dispersion Screening

Ann Newman · Pharmaceutical Sciences Encyclopedia · 2015

Finding the optimal form for drug development can involve a number of different screening activities, including a search for polymorphs, salts, cocrystals, and/or amorphous solid dispersions. High‐risk compounds will require special formulations that include amorphous solid dispersions. An amorphous dispersion screen is performed to find a suitable amorphous dispersion that exhibits acceptable properties. The screening performed in early development may focus on parameters such as solubility, supersaturation, short‐term physical and chemical stability, and animal bioavailability to get into early‐phase clinical trials quickly and establish proof of concept. Before starting an amorphous dispersion screen project, information on the active pharmaceutical ingredient (API) is needed. This may include chemical structure, solid form, physical stability, chemical stability, log P, hydrogen bond donors/acceptors, calculated solubility parameters, and known solubilities of the solid in various solvents/biorelevant media.

Cited by 12

Excitations of amorphous solid helium

J. Bossy, Jacques Ollivier, H. Schober et al. · Physical Review B · 2012

We present neutron scattering measurements of the dynamic structure factor $S(Q,\ensuremath{\omega})$ of amorphous solid helium confined in 47-\AA{} pore diameter MCM-41 at pressure 48.6 bars. At low temperature $T=0.05$ K, we observe $S(Q,\ensuremath{\omega})$ of the confined quantum amorphous solid plus the bulk polycrystalline solid between the MCM-41 powder grains. No liquidlike phonon-roton modes, other sharply defined modes at low energy ($\ensuremath{\omega}<$ 1.0 meV), or modes unique to a quantum amorphous solid that might suggest superflow are observed. Rather, the $S(Q,\ensuremath{\omega})$ of confined amorphous and bulk polycrystalline solid appear to be very similar. At higher temperature ($T>$ 1 K), the amorphous solid in the MCM-41 pores melts to a liquid which has a broad $S(Q,\ensuremath{\omega})$ peaked near $w\ensuremath{\simeq}0$, characteristic of normal liquid ${}^{4}$He under pressure. Expressions for the $S(Q,\ensuremath{\omega})$ of amorphous and polycrystalline solid helium are presented and compared. In previous measurements of liquid ${}^{4}$He confined in MCM-41 at lower pressure, the intensity in the liquid roton mode decreases with increasing pressure until the roton vanishes at the solidification pressure (38 bars), consistent with no roton in the solid observed here.

Cited by 8Open access

Volatility of Amorphous Solid Water

Mario Nachbar (5873135), Denis Duft (5873138), Thomas Leisner (2407957) · Figshare · 2018

Amorphous solid water\nis probably the most abundant form of solid\nwater in the universe. Its saturation vapor pressure and thermodynamic\nproperties, however, are not well known. We have investigated the\nsaturation vapor pressure over vapor-deposited amorphous ice at temperatures\nbetween 133 and 147 K using a novel experimental method. The new method\ndetermines the absolute vapor pressures and the sublimation rates\nby measuring the mass growth rates of ice-covered nanoparticles under\nsupersaturated water vapor conditions. We find that the vapor pressure\nof amorphous solid water is up to a factor of 3 higher than that predicted\nby current parameterizations, which are based in part on calorimetric\nmeasurements. We demonstrate that the calorimetric measurements can\nbe reconciled with our data by acknowledging the formation of nanocrystalline\nice as an intermediate ice phase during the crystallization of amorphous\nice. As a result, we propose a new value for the enthalpy of crystallization\nof amorphous solid water of Δ<i>H</i> = 2312 ±\n227 J/mol, which is about 1000 J/mol higher than the current consensus.\nOur results shine a new light on the abundance of water ice clouds\non Mars and mesospheric clouds on Earth and may alter our understanding\nof ice formation in the stratosphere.

Cited by 0Open access

Preparation of Amorphous Solid Water

David S. Olander, Stuart A. Rice · Proceedings of the National Academy of Sciences · 1972

A method of preparation of solid amorphous water is reported, along with a demonstration of the absence of crystalline ice. The samples described are the first to be completely free of contamination with crystalline ice.

Cited by 74Open access

Manufacturing Amorphous Solid Dispersions With Improved Solid-State Stability

Bhujbal, Sonal V · Figshare · 2021

Although amorphous solid dispersion(ASD) is a promising strategy for enhancing drug solubility, it has not been recognized to its full potential due to a lack of understanding as to how solid state stability is affected by manufacturing conditions such as method of preparation, formulation parameters (choice of excipients, drug-polymer ratio), processing conditions, and in part due to a lack of characterization techniques available to study drug-polymer miscibility and intermolecular interactions in the solid state. Therefore, to purpose of this research was to provide for a strong basis and insight to further develop robust and cheap ASD formulations. Chapter 1 discusses the relevant background, and specifies the objectives of this work in further detail. Chapter 2 is a detailed literature review providing an overview of the manufacturing techniques for preparing ASDs. As physical stability is a critical quality attribute for ASD, the impact of formulation, equipment, and process variables, together with the downstream processing on physical stability of ASDs have been discussed. Chapter 3 presents the development of an advanced surface characterization platform consisting of two complementary techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Such a platform enables qualitative and quantitative measurements of surface composition for the fine spray dried ASD particles with ultra-surface-sensitivity (less than 10 nm from the surface) and superior spatial resolution (approximately 250 nm for ToF-SIMS). In Chapter 4, spray-dried amorphous solid dispersions (ASD) of naproxen produced using a three fluid nozzle (3FN) were compared with those prepared using a two fluid nozzle (2FN) for physical stability. Upon storage of the formulated ASDs at different humidities, naproxen crystallized more quickly from the 3FN ASDs as compared with the 2FN ASDs. This relatively higher crystallization tendency of 3FN ASDs was attributed to the inhomogeneity of drug and polymer as identified by the solid-state Nuclear Magnetic Resonance findings, specifically due to poor mixing of water- and acetone-based solutions at the 3FN nozzle. This study provides insights into the effects of solvent and nozzle choices on the physical stability of spray-dried ASDs. Although processes like spray drying and melt extrusion enjoy widespread acceptance as commercial ASD manufacturing methods, their high capital cost of equipment discourages their application in developing countries. Chapter 5 and 6 aimed to develop amorphous solid dispersion (ASD) with a cost-effective manufacturing approach. Chapter 5 reports the development of lumefantrine ASDs by spray anti-solvent precipitation. The choice of polymer, and the drug-polymer ratio played a crucial role in the solubility enhancement of lumefantrine. Chapters 6 discusses the formulation ivermectin ASDs by a combination approach of anti-solvent precipitation followed by spray drying. ASDs of prepared by spray-drying alone exhibited a stability and dissolution profile similar to those prepared using the combination of precipitation and spray drying with the same drug load. This study indicates the developed manufacturing method of anti-solvent precipitation followed spray drying is a promising approach for producing ivermectin ASDs.

Cited by 0Open access

Manufacturing Amorphous Solid Dispersions with Improved Solid-State Stability

Bhujbal, Sonal · Figshare · 2021

Although amorphous solid dispersion(ASD) is a promising strategy for enhancing drug solubility, it has not been recognized to its full potential due to a lack of understanding as to how solid state stability is affected by manufacturing conditions such as method of preparation, formulation parameters (choice of excipients, drug-polymer ratio), processing conditions, and in part due to a lack of characterization techniques available to study drug-polymer miscibility and intermolecular interactions in the solid state. Therefore, to purpose of this research was to provide for a strong basis and insight to further develop robust and cheap ASD formulations. Chapter 1 discusses the relevant background, and specifies the objectives of this work in further detail. Chapter 2 is a detailed literature review providing an overview of the manufacturing techniques for preparing ASDs. As physical stability is a critical quality attribute for ASD, the impact of formulation, equipment, and process variables, together with the downstream processing on physical stability of ASDs have been discussed. Chapter 3 presents the development of an advanced surface characterization platform consisting of two complementary techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Such a platform enables qualitative and quantitative measurements of surface composition for the fine spray dried ASD particles with ultra-surface-sensitivity (less than 10 nm from the surface) and superior spatial resolution (approximately 250 nm for ToF-SIMS). In Chapter 4, spray-dried amorphous solid dispersions (ASD) of naproxen produced using a three fluid nozzle (3FN) were compared with those prepared using a two fluid nozzle (2FN) for physical stability. Upon storage of the formulated ASDs at different humidities, naproxen crystallized more quickly from the 3FN ASDs as compared with the 2FN ASDs. This relatively higher crystallization tendency of 3FN ASDs was attributed to the inhomogeneity of drug and polymer as identified by the solid-state Nuclear Magnetic Resonance findings, specifically due to poor mixing of water- and acetone-based solutions at the 3FN nozzle. This study provides insights into the effects of solvent and nozzle choices on the physical stability of spray-dried ASDs. Although processes like spray drying and melt extrusion enjoy widespread acceptance as commercial ASD manufacturing methods, their high capital cost of equipment discourages their application in developing countries. Chapter 5 and 6 aimed to develop amorphous solid dispersion (ASD) with a cost-effective manufacturing approach. Chapter 5 reports the development of lumefantrine ASDs by spray anti-solvent precipitation. The choice of polymer, and the drug-polymer ratio played a crucial role in the solubility enhancement of lumefantrine. Chapters 6 discusses the formulation ivermectin ASDs by a combination approach of anti-solvent precipitation followed by spray drying. ASDs of prepared by spray-drying alone exhibited a stability and dissolution profile similar to those prepared using the combination of precipitation and spray drying with the same drug load. This study indicates the developed manufacturing method of anti-solvent precipitation followed spray drying is a promising approach for producing ivermectin ASDs.

Cited by 0Open access

Manufacturing Amorphous Solid Dispersions With Improved Solid-State Stability

Bhujbal, Sonal V · Purdue · 2021

Although amorphous solid dispersion(ASD) is a promising strategy for enhancing drug solubility, it has not been recognized to its full potential due to a lack of understanding as to how solid state stability is affected by manufacturing conditions such as method of preparation, formulation parameters (choice of excipients, drug-polymer ratio), processing conditions, and in part due to a lack of characterization techniques available to study drug-polymer miscibility and intermolecular interactions in the solid state. Therefore, to purpose of this research was to provide for a strong basis and insight to further develop robust and cheap ASD formulations. Chapter 1 discusses the relevant background, and specifies the objectives of this work in further detail. Chapter 2 is a detailed literature review providing an overview of the manufacturing techniques for preparing ASDs. As physical stability is a critical quality attribute for ASD, the impact of formulation, equipment, and process variables, together with the downstream processing on physical stability of ASDs have been discussed. Chapter 3 presents the development of an advanced surface characterization platform consisting of two complementary techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Such a platform enables qualitative and quantitative measurements of surface composition for the fine spray dried ASD particles with ultra-surface-sensitivity (less than 10 nm from the surface) and superior spatial resolution (approximately 250 nm for ToF-SIMS). In Chapter 4, spray-dried amorphous solid dispersions (ASD) of naproxen produced using a three fluid nozzle (3FN) were compared with those prepared using a two fluid nozzle (2FN) for physical stability. Upon storage of the formulated ASDs at different humidities, naproxen crystallized more quickly from the 3FN ASDs as compared with the 2FN ASDs. This relatively higher crystallization tendency of 3FN ASDs was attributed to the inhomogeneity of drug and polymer as identified by the solid-state Nuclear Magnetic Resonance findings, specifically due to poor mixing of water- and acetone-based solutions at the 3FN nozzle. This study provides insights into the effects of solvent and nozzle choices on the physical stability of spray-dried ASDs. Although processes like spray drying and melt extrusion enjoy widespread acceptance as commercial ASD manufacturing methods, their high capital cost of equipment discourages their application in developing countries. Chapter 5 and 6 aimed to develop amorphous solid dispersion (ASD) with a cost-effective manufacturing approach. Chapter 5 reports the development of lumefantrine ASDs by spray anti-solvent precipitation. The choice of polymer, and the drug-polymer ratio played a crucial role in the solubility enhancement of lumefantrine. Chapters 6 discusses the formulation ivermectin ASDs by a combination approach of anti-solvent precipitation followed by spray drying. ASDs of prepared by spray-drying alone exhibited a stability and dissolution profile similar to those prepared using the combination of precipitation and spray drying with the same drug load. This study indicates the developed manufacturing method of anti-solvent precipitation followed spray drying is a promising approach for producing ivermectin ASDs.

Cited by 0Open access

Manufacturing Amorphous Solid Dispersions with Improved Solid-State Stability

Bhujbal, Sonal · Figshare · 2021

Although amorphous solid dispersion(ASD) is a promising strategy for enhancing drug solubility, it has not been recognized to its full potential due to a lack of understanding as to how solid state stability is affected by manufacturing conditions such as method of preparation, formulation parameters (choice of excipients, drug-polymer ratio), processing conditions, and in part due to a lack of characterization techniques available to study drug-polymer miscibility and intermolecular interactions in the solid state. Therefore, to purpose of this research was to provide for a strong basis and insight to further develop robust and cheap ASD formulations. Chapter 1 discusses the relevant background, and specifies the objectives of this work in further detail. Chapter 2 is a detailed literature review providing an overview of the manufacturing techniques for preparing ASDs. As physical stability is a critical quality attribute for ASD, the impact of formulation, equipment, and process variables, together with the downstream processing on physical stability of ASDs have been discussed. Chapter 3 presents the development of an advanced surface characterization platform consisting of two complementary techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Such a platform enables qualitative and quantitative measurements of surface composition for the fine spray dried ASD particles with ultra-surface-sensitivity (less than 10 nm from the surface) and superior spatial resolution (approximately 250 nm for ToF-SIMS). In Chapter 4, spray-dried amorphous solid dispersions (ASD) of naproxen produced using a three fluid nozzle (3FN) were compared with those prepared using a two fluid nozzle (2FN) for physical stability. Upon storage of the formulated ASDs at different humidities, naproxen crystallized more quickly from the 3FN ASDs as compared with the 2FN ASDs. This relatively higher crystallization tendency of 3FN ASDs was attributed to the inhomogeneity of drug and polymer as identified by the solid-state Nuclear Magnetic Resonance findings, specifically due to poor mixing of water- and acetone-based solutions at the 3FN nozzle. This study provides insights into the effects of solvent and nozzle choices on the physical stability of spray-dried ASDs. Although processes like spray drying and melt extrusion enjoy widespread acceptance as commercial ASD manufacturing methods, their high capital cost of equipment discourages their application in developing countries. Chapter 5 and 6 aimed to develop amorphous solid dispersion (ASD) with a cost-effective manufacturing approach. Chapter 5 reports the development of lumefantrine ASDs by spray anti-solvent precipitation. The choice of polymer, and the drug-polymer ratio played a crucial role in the solubility enhancement of lumefantrine. Chapters 6 discusses the formulation ivermectin ASDs by a combination approach of anti-solvent precipitation followed by spray drying. ASDs of prepared by spray-drying alone exhibited a stability and dissolution profile similar to those prepared using the combination of precipitation and spray drying with the same drug load. This study indicates the developed manufacturing method of anti-solvent precipitation followed spray drying is a promising approach for producing ivermectin ASDs.

Cited by 0Open access

Release Mechanisms of Amorphous Solid Dispersions

Yang, Ruochen · Purdue · 2022

As the pharmaceutical industry moves towards molecular obesity with the use of high throughput screening for identification of promising candidates, the low aqueous solubilities of new chemical entities pose significant challenges to achieving adequate oral absorption and bioavailability. Enabling formulations are often needed to address this issue. Amorphous solid dispersion (ASD), where an amorphous drug and a polymer are molecularly mixed, has gained popularity as a dissolution/solubility enhancing strategy over the years. Upon ASD dissolution, the release rate of drug is much higher than that of the neat amorphous form of the drug. More importantly, the apparent concentration of drug in the solution can exceed its amorphous solubility through the formation of a drug-rich colloidal phase in the solution, also called nanodroplets. The presence of nanodroplets has been shown to be beneficial for oral absorption and bioavailability and their formation during release is therefore desirable. However, such release profiles are only achieved at relatively low drug loadings (DLs) and release tends to drop with increasing DL. For ASDs based on polyvinylpyrrolidone/vinyl acetate (PVPVA), drug release drops drastically once the DL exceeds a certain value, called limit of congruency (LoC). The low DL at which the ASD demonstrates good release also presents additional challenges since it can create a pill burden for patients due to the large amount of polymer needed in the formulation. Therefore, to achieve optimal drug product performance, it is crucial to understand the mechanisms of drug release. Therefore, this thesis focuses on understanding the factors affecting, and the mechanisms of ASD drug release, as well as enhancing drug release through addition of surfactants. The glass transition temperature of a drug and its interaction with the polymer were identified as important factors affecting the drug release and LoC. Another phase transition occurring during ASD hydration/dissolution, amorphous-amorphous phase separation (AAPS), was shown to affect drug release from ASD significantly. During dissolution, water-induced AAPS occurs, and the initially miscible ASD separates into two phases, an insoluble drug-rich phase and a soluble water/polymer-rich phase. The formation of a continuous drug-rich phase at the ASD-solution interface was shown to be detrimental to drug release as it could act as barrier that blocked any further drug release. When the drug-rich phase formed adopted a discrete morphology or when phase separation occurred in the solution outside of the dissolving ASD matrix, good release could be achieved. Surfactants could interrupt the formation of the continuous drug-rich both kinetically and thermodynamically, improving drug release as a result. Other mechanisms of release enhancement by surfactants included increased polymer release rate, increased water ingress and plasticization. The findings in this thesis will provide insight into ASD release mechanisms, and facilitate rational excipient selection when designing ASD formulations.

Cited by 0Open access