Effect of guest drug character encapsulated in the cavity and intermolecular spaces of γ-cyclodextrins on the dissolution property of ternary γ-cyclodextrin complex

Febuxostat ternary inclusion complex using SBE7-βCD in presence of a water-soluble polymer: physicochemical characterization, in vitro dissolution, and in vivo evaluation

Febuxostat (FBX), a potent xanthine oxidase inhibitor, is widely used as a blood uric acid-reducing agent and has recently shown a promising repurposing outcome as an anti-cancer. FBX is known for its poor water solubility, which is the main cause of its weak oral bioavailability. In a previous study, we developed a binary system complex between FBX and sulfobutylether-β-cyclodextrin (SBE7-βCD) with improved dissolution behavior. The aim of the current study was to investigate the effect of incorporating a water-soluble polymer with a binary system forming a ternary one, on further enhancement of FBX solubility and dissolution rate. In vivo oral bioavailability was also studied using LC-MS/MS chromatography. The polymer screening study revealed a marked increment in the solubility of FBX with SBE7-βCD in the presence of 5% w/v polyethylene glycol (PEG 6000). In vitro release profile showed a significant increase in the dissolution rate of FBX from FBX ternary complex (FTC). Oral in vivo bioavailability of prepared FTC showed more than threefold enhancement in Cmax value (17.05 ± 2.6 µg/mL) compared to pure FBX Cmax value (5.013 ± 0.417 µg/mL) with 257% rise in bioavailability. In conclusion, the association of water-soluble polymers with FBX and SBE7-βCD system could significantly improve therapeutic applications of the drug.

Discrimination of β-cyclodextrin/hazelnut (Corylus avellana L.) oil/flavonoid glycoside and flavonolignan ternary complexes by Fourier-transform infrared spectroscopy coupled with principal component analysis

The goal of the study was the discrimination of β-cyclodextrin (β-CD)/hazelnut (Corylus avellana L.) oil/antioxidant ternary complexes through Fourier-transform infrared spectroscopy coupled with principal component analysis (FTIR-PCA). These innovative complexes combine the characteristics of the three components and improve the properties of the resulting material such as the onsite protection against oxidative degradation of hazelnut oil unsaturated fatty acid glycerides. Also, the apparent water solubility and bioaccessibility of the hazelnut oil components and antioxidants can be increased, as well as the controlled release of bioactive compounds (fatty acid glycerides and antioxidant flavonoids, namely hesperidin, naringin, rutin, and silymarin). The appropriate method for obtaining the ternary complexes was kneading the components at various molar ratios (1:1:1 and 3:1:1 for β-CD hydrate:hazelnut oil (average molar mass of 900 g/mol):flavonoid). The recovering yields of the ternary complexes were in the range of 51.5-85.3% and were generally higher for the 3:1:1 samples. The thermal stability was evaluated by thermogravimetry and differential scanning calorimetry. Discrimination of the ternary complexes was easily performed through the FTIR-PCA coupled method, especially based on the stretching vibrations of CO groups in flavonoids and/or CO/CC groups in the ternary complexes at 1014.6 (± 3.8) and 1023.2 (± 1.1) cm^-1 along the second PCA component (PC₂), respectively. The wavenumbers were more appropriate for discrimination than the corresponding intensities of the specific FTIR bands. On the other hand, ternary complexes were clearly distinguishable from the starting β-CD hydrate along the first component (PC₁) by all FTIR band intensities and along PC₂ by the wavenumber of the asymmetric stretching vibrations of the CH groups at 2922.9 (± 0.4) cm^-1 for ternary complexes and 2924.8 (± 1.4) cm^-1 for β-CD hydrate. The first two PCA components explain 70.38% from the variance of the FTIR data (from a total number of 26 variables). Other valuable classifications were obtained for the antioxidant flavonoids, with a high similarity for hesperidin and naringin, according to FTIR-PCA, as well as for ternary complexes depending on molar ratios. The FTIR-PCA coupled technique is a fast, nondestructive and cheap method for the evaluation of quality and similarity/characteristics of these new types of cyclodextrin-based ternary complexes having enhanced properties and stability.

Computational approach to elucidate the formation and stabilization mechanism of amorphous formulation using molecular dynamics simulation and fragment molecular orbital calculation

α-Glycosyl rutin (Rutin-G) consists of a flavonol skeleton and sugar groups and is a promising additive for amorphous formulations. In our previous study, experimental approaches suggested an interaction between the model drug carbamazepine (CBZ) and flavonol skeleton of Rutin-G that stabilizes amorphous formulations. In the present study, the formation and stabilization mechanisms of CBZ/Rutin-G amorphous formulation were investigated using a computational approach. The CBZ/Rutin-G amorphous formulation was obtained via molecular dynamics (MD) simulation, which mimicked the melt-quenching method. Root mean square deviation analysis revealed that the translational motion of CBZ during the cooling process was suppressed by adding Rutin-G. Monitoring the atomic distance during the cooling process revealed that hydrogen bonds via carboxamide oxygen of CBZ with hydroxyl hydrogen of Rutin-G were preferentially formed with flavonol skeletons than sugar groups. The simulated amorphous formulation was then calculated using fragment molecular orbital (FMO) method. The quantitative evaluation of multiple interactions revealed that the hydrogen bond energy was higher in CBZ-sugar groups than in CBZ-flavonol skeleton, while the π-type of interaction energy was higher in CBZ-flavonol skeleton than in CBZ-sugar groups. The computational approach combining MD simulation and FMO calculation provides information on various interactions that are difficult to detect using experimental approaches, which helps understand the formation and stabilization mechanism of amorphous formulations.

Molecular Recognition of Fluorescent Probe Molecules with a Pseudopolyrotaxane Nanosheet

Pseudopolyrotaxane nanosheets (PPRNS) are ultrathin two-dimensional (2D) materials fabricated via supramolecular self-assembly of β-cyclodextrin (β-CD) and poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers. In this study, the molecular loading of various fluorescent probe molecules onto PPRNS was systematically investigated. ¹H NMR study for R6G absorption to PPRNS indicated that the small hydrophobic groups, such as the methyl group, of R6G were absorbed by PPRNS. Consistently, the fluorescent probes without methyl groups were not absorbed. These results indicate that PPRNS has a molecular recognition absorption property based on the host-guest interaction of the functional groups on probe molecules and molecular-sized spaces of PPRNS surfaces, which may be vacant β-CDs and voids between β-CD columns. The absorbed amount of the molecular probes onto PPRNS was investigated by UV-vis spectra, and the absorption behavior could be described well by the Langmuir absorption isotherm. This is consistent with the suggested model that the probes are absorbed onto the PPRNS surfaces. This study demonstrates that PPRNSs can be applied as adsorbents for toxic compounds, drug delivery systems, and 2D sensors.

Carbohydrate-based nanomaterials for biomedical applications

Carbohydrates are abundant biomolecules, with a strong tendency to form supramolecular networks. A host of carbohydrate-based nanomaterials have been exploited for biomedical applications. These structures are based on simple mono- or disaccharides, as well as on complex, polymeric systems. Chemical modifications serve to tune the shapes and properties of these materials. In particular, carbohydrate-based nanoparticles and nanogels were used for drug delivery, imaging, and tissue engineering applications. Due to the reversible nature of the assembly, often based on a combination of hydrogen bonding and hydrophobic interactions, carbohydrate-based materials are valuable substrates for the creations of responsive systems. Herein, we review the current research on carbohydrate-based nanomaterials, with a particular focus on carbohydrate assembly. We will discuss how these systems are formed and how their properties are tuned. Particular emphasis will be placed on the use of carbohydrates for biomedical applications. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

[Design Features in the Molecular-level Development of Solid Pharmaceutical Formulations Based on Supramolecular Structures]

We focused on the crystal structure of cyclodextrin (CD) to develop new solid CD complexes. There are two large spaces in the columnar structure of CD crystals: one inside a CD cavity and another between CD columns. New solid CD complexes can be designed by incorporating guest drugs between the CD columns. We succeeded in preparing a solid drug/[polyethylene glycol (PEG)/γ-CD-polypseudoraxane (PPRX)] complex by a sealed-heating method via the gas phase. A drug/(PEG/γ-CD-PPRX) complex has a structure in which PEGs are included in a γ-CD cavity, and guest drugs are incorporated between the γ-CD columns. Screening by a sealed-heating method determined that a variety of guest drugs with varying molecular size and log P could be incorporated into the spaces between γ-CD columns, following a stoichiometric rule. Another method, via solid phase using cogrinding and subsequent heating, was developed to prepare drug/(PEG/γ-CD-PPRX) complex. This method enabled us to prepare the complex with a thermally unstable drug, as well as a drug/(PEG/α-CD-PPRX) complex not formed using the sealed-heating method. Both the structure and molecular state of each drug in the complexes were characterized by powder X-ray diffraction and solid-state NMR measurements. The dissolution character and thermal stability of the drug incorporated in the complex could be improved by the specific complex formation. The solid CD complexes thus developed have potential for drug-encapsulation and as drug-release carriers, owing to their unique structural and pharmaceutical properties.

Supramolecular Pharmaceutical Sciences: A Novel Concept Combining Pharmaceutical Sciences and Supramolecular Chemistry with a Focus on Cyclodextrin-Based Supermolecules

Supramolecular chemistry is an extremely useful and important domain for understanding pharmaceutical sciences because various physiological reactions and drug activities are based on supramolecular chemistry. However, it is not a major domain in the pharmaceutical field. In this review, we propose a new concept in pharmaceutical sciences termed "supramolecular pharmaceutical sciences," which combines pharmaceutical sciences and supramolecular chemistry. This concept could be useful for developing new ideas, methods, hypotheses, strategies, materials, and mechanisms in pharmaceutical sciences. Herein, we focus on cyclodextrin (CyD)-based supermolecules, because CyDs have been used not only as pharmaceutical excipients or active pharmaceutical ingredients but also as components of supermolecules.