Water Uptake, Distribution, and Mobility in Amorphous Poly( d , l ‐Lactide) by Molecular Dynamics Simulation

Xiang, Tian‐Xiang; Anderson, Bradley D.

doi:10.1002/jps.23855

Cited by 28 publications

(18 citation statements)

References 84 publications

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“…They also performed MD simulations for polymers such as hypromellose acetate succinate and poly-lactide (184,185). The investigations used dry amorphous indomethacin, as the simulation only used 0.6% w /w water molecules (183).…”

Section: The Need For Methods To Better Understand the Processes Occumentioning

confidence: 99%

The Need for Restructuring the Disordered Science of Amorphous Drug Formulations

2017

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The alarming numbers of poorly soluble discovery compounds have centered the efforts towards finding strategies to improve the solubility. One of the attractive approaches to enhance solubility is via amorphization despite the stability issue associated with it. Although the number of amorphous-based research reports has increased tremendously after year 2000, little is known on the current research practice in designing amorphous formulation and how it has changed after the concept of solid dispersion was first introduced decades ago. In this review we try to answer the following questions: What model compounds and excipients have been used in amorphous-based research? How were these two components selected and prepared? What methods have been used to assess the performance of amorphous formulation? What methodology have evolved and/or been standardized since amorphous-based formulation was first introduced and to what extent have we embraced on new methods? Is the extent of research mirrored in the number of marketed amorphous drug products? We have summarized the history and evolution of amorphous formulation and discuss the current status of amorphous formulation-related research practice. We also explore the potential uses of old experimental methods and how they can be used in tandem with computational tools in designing amorphous formulation more efficiently than the traditional trial-and-error approach.

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Section: The Need For Methods To Better Understand the Processes Occumentioning

confidence: 99%

The Need for Restructuring the Disordered Science of Amorphous Drug Formulations

2017

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“…These reorientational correlation functions (ROCF) often display stretched exponential decay, a characteristic of the Kohlrausch–Williams–Watts (KWW) 44–46 law that is used to describe the relaxation of various phenomena in complex condensed matter systems. 47,48 This technique has not only been applied to the study of the hydration shells of proteins, 49,50 but also to water confined near inorganic surfaces and other fullerene-containing systems. 23,26–28,51 The KWW equation

C_{β} false(t false) = {Ae}^{- {false(t / τ false)}^{β}}

where A is a prefactor, β is the stretched exponential constant, and τ is the central relaxation time can be fit to the ROCF to extract information about the dynamics.…”

Section: Methodsmentioning

confidence: 99%

Solvation of Carbon Nanoparticles in Water/Alcohol Mixtures: Using Molecular Simulation To Probe Energetics, Structure, and Dynamics

Hinkle

Phelan

2017

J. Phys. Chem. C

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Molecular dynamics simulations were used to examine the solvation behavior of buckminsterfullerene and single-walled carbon nanotubes (SWCNT) in a range of water/alcohol solvent compositions at 1 atm and 300 K. Results indicate that the alcohols assume the role of pseudosurfactants by shielding the nanotube from the more unfavorable interactions with polar water molecules. This is evident in both the free energies of transfer (ΔΔGwater→xOH = −68.1 kJ/mol and −86.5 kJ/mol for C60 in methanol and ethanol; ΔΔGwater→xOH = −345.6 kJ/mol and −421.2 kJ/mol for the (6,5)-SWCNT in methanol and ethanol) and the composition of the solvation shell at intermediate alcohol concentrations. Additionally, we have observed the retardation of both the translational and rotational dynamics of molecules near the nanoparticle surface through use of time correlation functions. A 3-fold increase in the residence times of the alcohol molecules within the solvation shells at low concentrations further reveals their surfactant-like behavior. Such interactions are important when considering the complex molecular environment present in many schemes used for nanoparticle purification techniques.

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“…III. The latter also known as Kohlrausch-Williams-Watts (KWW) law is widely employed in the characterization of the non-exponential nature of relaxations in several phenomena in complex condensed matter systems, 104,105 and recently, it has been used to explain the residence times of the hydration water of proteins, confined water near inorganic surfaces and pores, and fullerene-containing systems. 74,97,106,107 The KWW function is given by 108,109…”

Section: Simulation Setup and Computed Propertiesmentioning

confidence: 99%

Water around fullerene shape amphiphiles: A molecular dynamics simulation study of hydrophobic hydration

Varanasi

Guskova

John

et al. 2015

The Journal of Chemical Physics

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Fullerene C60 sub-colloidal particle with diameter ∼1 nm represents a boundary case between small and large hydrophobic solutes on the length scale of hydrophobic hydration. In the present paper, a molecular dynamics simulation is performed to investigate this complex phenomenon for bare C60 fullerene and its amphiphilic/charged derivatives, so called shape amphiphiles. Since most of the unique properties of water originate from the pattern of hydrogen bond network and its dynamics, spatial, and orientational aspects of water in solvation shells around the solute surface having hydrophilic and hydrophobic regions are analyzed. Dynamical properties such as translational-rotational mobility, reorientational correlation and occupation time correlation functions of water molecules, and diffusion coefficients are also calculated. Slower dynamics of solvent molecules—water retardation—in the vicinity of the solutes is observed. Both the topological properties of hydrogen bond pattern and the "dangling" -OH groups that represent surface defects in water network are monitored. The fraction of such defect structures is increased near the hydrophobic cap of fullerenes. Some "dry" regions of C60 are observed which can be considered as signatures of surface dewetting. In an effort to provide molecular level insight into the thermodynamics of hydration, the free energy of solvation is determined for a family of fullerene particles using thermodynamic integration technique.

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Water Uptake, Distribution, and Mobility in Amorphous Poly( d , l ‐Lactide) by Molecular Dynamics Simulation

Cited by 28 publications

References 84 publications

The Need for Restructuring the Disordered Science of Amorphous Drug Formulations

The Need for Restructuring the Disordered Science of Amorphous Drug Formulations

Solvation of Carbon Nanoparticles in Water/Alcohol Mixtures: Using Molecular Simulation To Probe Energetics, Structure, and Dynamics

Water around fullerene shape amphiphiles: A molecular dynamics simulation study of hydrophobic hydration

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