Conformational stability of ibuprofen: assessed by DFT calculations and optical vibrational spectroscopy

β-TCP porous pellets as an orthopaedic drug delivery system: ibuprofen/carrier physicochemical interactions

Calcium phosphate bone substitute materials can be loaded with active substances for in situ, targeted drug administration. In this study, porous β-TCP pellets were investigated as an anti-inflammatory drug carrier. Porous β-TCP pellets were impregnated with an ethanolic solution of ibuprofen. The effects of contact time and concentration of ibuprofen solution on drug adsorption were studied. The ibuprofen adsorption equilibrium time was found to be one hour. The adsorption isotherms fitted to the Freundlich model, suggesting that the interaction between ibuprofen and β-TCP is weak. The physicochemical characterizations of loaded pellets confirmed that the reversible physisorption of ibuprofen on β-TCP pellets is due to Van der Waals forces, and this property was associated with the 100% ibuprofen release.

Raman spectroscopy of racemic ibuprofen: evidence of molecular disorder in phase II

Low- and high-frequency Raman experiments in the 5-200 cm(-1) and 600-1800 cm(-1) ranges were carried out in the crystalline and amorphous states of ibuprofen. Low-frequency investigations indubitably reveal the existence of a molecular disorder in the metastable phase (phase II), through the observation of quasielastic contribution below 30 cm(-1), and the absence of phonon peaks in the Raman susceptibility which mimics the density of vibrational states of an amorphous state. High-frequency Raman spectra indicate a local order in phase II similar to that in the glassy state. Both dynamic and static molecular disorder could contribute to the Raman signatures of the disorder in crystalline phase II. Raman investigations suggest that phase II can be considered as a transient metastable state in the devitrification process of ibuprofen upon heating from a far from equilibrium state toward the stable phase I.

Molecular dynamics simulations of Ibuprofen binding to Abeta peptides

Using replica exchange molecular dynamics simulations and the implicit solvent model we probed binding of ibuprofen to Abeta(10-40) monomers and amyloid fibrils. We found that the concave (CV) fibril edge has significantly higher binding affinity for ibuprofen than the convex edge. Furthermore, binding of ibuprofen to Abeta monomers, as compared to fibrils, results in a smaller free energy gain. The difference in binding free energies is likely to be related to the presence of the groove on the CV fibril edge, in which ibuprofen tends to accumulate. The confinement effect of the groove promotes the formation of large low-energy ibuprofen clusters, which rarely occur on the surface of Abeta monomers. These observations led us to suggest that the ibuprofen binding mechanism for Abeta fibrils is different from that for monomers. In general, ibuprofen shows a preference to bind to those regions of Abeta monomers (amino terminal) and fibrils (the CV edge) that are also the primary aggregation interfaces. Based on our findings and on available experimental data, we propose a rationale for the ibuprofen antiaggregation effect.

Effect of Ultrasound on the Compaction of Ibuprofen/Isomalt Systems

Six mixtures, containing 10, 20 and 30% w/w ibuprofen and isomalt, were compacted by a traditional or ultrasound-assisted machine and analysed by means of thermal (DSC and TGA) and micro-spectrometry (Raman and FT-IR) techniques. Ultrasound discharge causes melting of ibuprofen powder, transforming into a paste that could not assume the shape of a tablet; when in mixture with isomalt, thermal events, occurring during ultrasound compaction, change the appearance of the particles formed by milling the tablets obtained this way and SEM photos reveal a dramatic reduction of the particle size and changes due to a possible ibuprofen re-crystallization. Raman and FT-IR spectra of small portions of the surface and of the bulk, using characteristic peaks for identification, reveal that in ultrasound-compacted tablets ibuprofen partially disappears from the top face of the tablet.

A revised conformational code for the exhaustive analysis of conformers with one-to-one correspondence between conformation and code: application to the VCD analysis of (S)-ibuprofen

A revised conformational code for the exhaustive analysis of conformers of all classes of molecules is proposed and applied to the vibrational circular dichroism (VCD) analysis of (S)-ibuprofen. The revised code can strictly define the conformation of compounds with relatively high-symmetry substituents and is especially useful for visualizing conformational changes in ligands and proteins. The conformational analysis of (S)-ibuprofen using the code in the solution state reveals that the four energetically preferred conformations, ibut-3alpha2alpha sigma(phpa-3alpha sigma2alpha), ibut-3alpha2alpha tau(phpa-3alpha tau2alpha), ibut-2beta3beta tau(phpa-3alpha tau2alpha), and ibut-2beta3beta sigma(phpa-3alpha sigma2alpha), exist in the monomer and dimer forms. In CDCl(3) solution, the dimer form is stabilized as the "U"-shape, and the ease of crystallization is largely ascribed to the conformation of phpa-3alpha2alpha for (S)-ibuprofen. The new version of the conformational code has the possibility to be used as a tool for the exhaustive analysis of conformers of all kinds of chemical compounds, conformome analysis, and in the future for metabolome, proteome, and genome analyses.