Dynamics of Clay-Intercalated Ibuprofen Studied by Solid State Nuclear Magnetic Resonance

Role of Exchange Cations and Layer Charge on the Dynamics of Confined Water

Describing the dynamic behavior of water confined in clay minerals is a fascinating challenge and crucial in many research areas, ranging from materials science and geotechnical engineering to environmental sustainability. Water is the most abundant resource on Earth, and the high reactivity of naturally occurring hydrous clay minerals used since prehistoric times for a variety of applications means that water-clay interaction is a ubiquitous phenomenon in nature. We have attempted to experimentally distinguish the rotational dynamics and translational diffusion of two distinct populations of interlayer water, confined and ultraconfined, in the sodium (Na) forms of two smectite clay minerals, montmorillonite (Mt) and hectorite (Ht). Samples hydrated at a pseudo one-layer hydration (1LH) state under ambient conditions were studied with quasi-elastic neutron scattering (QENS) between 150 and 300 K. Using a simplified revised jump-diffusion and rotation-diffusion model (srJRM), we observed that while interlayer water near the ditrigonal cavity in Ht forms strong H-bonds to both adjacent surface O and structural OH, H-bonding of other more prevalent interlayer water with the surface O is weaker compared to Mt, inducing a higher temperature for dynamical changes of confined water. Given the lower layer charge and faster dynamics observed for Ht compared to Mt, we consider this strong evidence confirming the influence of the interlayer cation and surfaces on confined water dynamics.

Combining X-ray and NMR Crystallography to Explore the Crystallographic Disorder in Salbutamol Oxalate

Salbutamol is an active pharmaceutical ingredient commonly used to treat respiratory distress and is listed by the World Health Organization as an essential medicine. Here, we establish the crystal structure of its oxalate form, salbutamol oxalate, and explore the nature of its crystallographic disorder by combined X-ray crystallography and ¹³C cross-polarization (CP) magic-angle spinning (MAS) solid-state NMR. The *C-OH chiral center of salbutamol (note that the crystal structures are a racemic mixture of the two enantiomers of salbutamol) is disordered over two positions, and the tert-butyl group is rotating rapidly, as revealed by ¹³C solid-state NMR. The impact of crystallization conditions on the disorder was investigated, finding variations in the occupancy ratio of the *C-OH chiral center between single crystals and a consistency across samples in the bulk powder. Overall, this work highlights the contrast between investigating crystallographic disorder by X-ray diffraction and solid-state NMR experiment, and gauge-including projector-augmented-wave (GIPAW) density functional theory (DFT) calculations, with their combined use, yielding an improved understanding of the nature of the crystallographic disorder between the local (i.e., as viewed by NMR) and longer-range periodic (i.e., as viewed by diffraction) scale.

Preparation, Characterization, and In Vitro Performance of Gambogic Acid-Layered Double Hydroxide/Liposome Nanocomposites

Gambogic acid (GA) refers to a xanthonoid that exhibits significant antitumor activity due to its poor solubility and low bioavailability. For this reason, its shortcoming should be overcome using novel approaches to improve its practical effectiveness. In this study, with the use of ion exchange method, GA was encapsulated in layered double hydroxide (LDH). In the GA-LDH nanohybrid, GA was distributed and stabilized in the interlamellar region of LDH through intermolecular interactions. GA-LDH was further modified by liposome (LS) through ethanol injection method. The drug encapsulation efficiency of GA-LDH/LS was obtained as 56.28%. The chemical structures and physicochemical properties exhibited by GA-LDH/LS were characterized and confirmed using different instruments, and drug release showed that GA-LDH/LS had significantly sustained release due to the combined effect of the matrix LDH and the phospholipid bilayer. Furthermore, GA-LDH/LS displayed lower hemolysis percentage than GA-LDH during the hemolysis test. This study suggested that GA-LDH/LS nanocomposite could be a promising antitumor drug delivery system due to its outstanding performance in biomedical research.

The role of water in the confinement of ibuprofen in SBA-15

The introduction of ibuprofen into mesopores of SBA-15 has been accomplished using the melting method. Samples exhibit from 9 to 33% of the hydrophobic drug. They are not toxic to mouse monocyte-macrophage cells and do not stimulate a pro-inflammatory response. The sample with 25% of the drug showed no crystalline ibuprofen and almost filled the mesopores, while the sample with 33% showed a total filling of the mesopores with some crystalline ibuprofen present. By means of 1D (¹H, ¹³C HPDEC, ¹³C CP MAS) and 2D (¹H-¹H NOESY) MAS NMR spectroscopy, it has been shown that water coexists with ibuprofen in mesopores and has an impact on the mobility of ibuprofen molecules and their location within the sample (outside or inside mesopores). Studies in the dehydrated state show for the first time that the high mobility of ibuprofen in mesopores is directly connected to the presence of water. Dehydrated samples show slightly slower release rates in comparison to their hydrated counterparts.

Taming the dynamics in a pharmaceutical by cocrystallization: investigating the impact of the coformer by solid-state NMR

The anti-HIV pharmaceutical efavirenz is highly dynamic in its crystalline state, and we show that these dynamics can be tamed through the introduction of a coformer.

New nanocarried phenobarbital formulation: Maintains better control of pentylenetetrazole-Induced seizures

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For the first time, phenobarbital was intercalated in the layered double hydroxide.

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This study evaluated the slow release efficacy of intercalated phenobarbital.

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The time of the anticonvulsant effect was verified by electroencephalographic records.

This study aims to evaluate the efficacy of slow release phenobarbital in the control of convulsions triggered by pentylenetetrazole (PTZ), verifying the time of permanence in the anticonvulsant effect through behavior and electroencephalographic records. A total of 162 male Wistar rats weighing between 100 and 120 g were divided into two groups, one for behavior analysis (n = 90) and biochemistry, and another for the acquisition of electrocorticographic record (n = 72). Hepatic enzymes were measured by obtaining a blood sample from the animals studied by means of a biochemical analysis. The procedures for electrode implant and electrocorticographic recordings were performed. The intercalation of phenobarbital in layered double hydroxide (LDH) nanocarrier allowed us to evaluate a new slow release pharmaceutical formulation based on methodologies that have proven longer residence time and lower side effects. This study demonstrates that phenobarbital can be a new perspective pharmaceutical formulation.

Solid State NMR Study of the Mixing Degree Between Ginkgo Biloba Extract and a Soy-Lecithin-Phosphatidylserine in a Composite Prepared by the Phytosome® Method

Leaves extract of Ginkgo biloba, known in China since the most ancient times, has been widely used in the area of senile dementia thanks to its improving effects on cognitive function. A promising formulation of this botanical ingredient consists in a Ginkgo biloba-soy-lecithin-phosphatidylserine association obtained by the Phytosome® process. The precise assessment of the mixing degree between Ginkgo biloba and soy-lecithin-phosphatidylserine in this formulation is an important piece of information for understanding the reasons of its final performances. To this aim in the present study we carried out for the first time a Solid State Nuclear Magnetic Resonance investigation on Ginkgo biloba-soy-lecithin-phosphatidylserine association, on its constituents and on a mechanical mixture. The analysis of different observables highlighted a very intimate mixing (domains of single components not larger than 60 nm) of Ginkgo biloba and soy-lecithin-phosphatidylserine in their association obtained by Phytosome® process, together with a slight modification of their molecular dynamics, not observed in the case of the mechanical mixture.