The guest polymer effect on the dissolution of drug–polymer crystalline inclusion complexes

Electrospun Nanofibers with Pomegranate Peel Extract as a New Concept for Treating Oral Infections

Pomegranate peel extract is known for its potent antibacterial, antiviral, antioxidant, anti-inflammatory, wound healing, and probiotic properties, leading to its use in treating oral infections. In the first stage of this work, for the first time, using the Design of Experiment (DoE) approach, pomegranate peel extract (70% methanol, temperature 70 °C, and three cycles per 90 min) was optimized and obtained, which showed optimal antioxidant and anti-inflammatory properties. The optimized extract showed antibacterial activity against oral pathogenic bacteria. The second part of this study focused on optimizing an electrospinning process for a combination of polycaprolactone (PCL) and polyvinylpyrrolidone (PVP) nanofibers loaded with the optimized pomegranate peel extract. The characterization of the nanofibers was confirmed by using SEM pictures, XRPD diffractograms, and IR-ATR spectra. The composition of the nanofibers can control the release; in the case of PVP-based nanofibers, immediate release was achieved within 30 min, while in the case of PCL/PVP, controlled release was completed within 24 h. Analysis of the effect of different scaffold compositions of the obtained electrofibers showed that those based on PCL/PVP had better wound healing potential. The proposed strategy to produce electrospun nanofibers with pomegranate peel extract is the first and innovative approach to better use the synergy of biological action of active compounds present in extracts in a patient-friendly pharmaceutical form, beneficial for treating oral infections.

Phase Identification and Discovery of an Elusive Polymorph of Drug-Polymer Inclusion Complex Using Automated 3D Electron Diffraction

3D electron diffraction (3D ED) has shown great potential in crystal structure determination in materials, small organic molecules, and macromolecules. In this work, an automated, low-dose and low-bias 3D ED protocol has been implemented to identify six phases from a multiple-phase melt-crystallisation product of an active pharmaceutical ingredient, griseofulvin (GSF). Batch data collection under low-dose conditions using a widely available commercial software was combined with automated data analysis to collect and process over 230 datasets in three days. Accurate unit cell parameters obtained from 3D ED data allowed direct phase identification of GSF Forms III, I and the known GSF inclusion complex (IC) with polyethylene glycol (PEG) (GSF-PEG IC-I), as well as three minor phases, namely GSF Forms II, V and an elusive new phase, GSF-PEG IC-II. Their structures were then directly determined by 3D ED. Furthermore, we reveal how the stabilities of the two GSF-PEG IC polymorphs are closely related to their crystal structures. These results demonstrate the power of automated 3D ED for accurate phase identification and direct structure determination of complex, beam-sensitive crystallisation products, which is significant for drug development where solid form screening is crucial for the overall efficacy of the drug product.

Molecular insights into the formation of drug-polymer inclusion complex

Drug-polymer inclusion complex (IC) has been viewed as a novel solid form of drugs for property modification. Nonetheless, our understanding of the formation mechanism remains limited. This work aims to provide insight into the molecular processes governing the structural construction of carbamazepine (CBZ) and griseofulvin (GSF) channel-type ICs in the presence of guest polymers. Leveraging microdroplet melt crystallization, we successfully unveiled the single-crystal structures of these ICs, enabling structural analysis, density functional theory calculations, and molecular dynamics simulations. The results collectively elucidate the disparity between CBZ and GSF channels in terms of their autonomy in the absence of guest polymers. CBZ molecules can spontaneously assemble into stable channel structures independently, capitalizing on their unique mortise-tenon architecture and robust π…π interactions. Conversely, GSF channels lack sufficient support from weak Cl…O and C-H…π intermolecular interactions and necessitate the insertion of guest molecules to stabilize their structures. We further calculated the eleven structurally determined drug-polymer ICs and found that their channel sizes consistently fall within a narrow range of 3.81-5.18 Å although they adopt diverse approaches to construct channel structures. We anticipate that these findings will inspire continued exploration of this novel solid form, facilitating theoretical predictions and practical applications in pharmaceutical development.