Revealing Polymorphic Phase Transformations in Polymer-Based Hot Melt Extrusion Processes

Unveiling a Novel Solvatomorphism of Anti-inflammatory Flufenamic Acid: X-ray Structure, Quantum Chemical, and In Silico Studies

This paper delves into the polymorphism of 2-[3-(trifluoromethyl)anilino]benzoic acid, commonly referred to as flufenamic acid (FA), a pharmaceutical agent employed in treating inflammatory conditions. The central focus of the study is on a newly unearthed solvatomorphic structure of FA in methanol (FAM), and a thorough comparison is conducted with the commercially available standard structure. Employing a comprehensive approach, including X-ray crystallography, Hirshfeld surface analysis, density functional theory (DFT), molecular docking, and molecular dynamics (MD) simulations, the research aims to unravel the structural and functional implications of solvatomorphism. The X-ray crystal structure analysis brings to light notable differences between the standard FA and solvatomorphic FAM, showcasing variations in intermolecular interactions and crystal packing. Key features such as hydrogen bonding, π···π stacking, and C-H···π interactions are identified as influential factors shaping the stability and conformation of the compounds. Hirshfeld surface analysis further quantifies the nature and contribution of intermolecular interactions, providing a comprehensive perspective on molecular stability. Density functional theory offers valuable electronic structure insights, highlighting disparities in frontier molecular orbitals between FA and FAM. Molecular docking studies against prostaglandin D2 11-ketoreductase explore potential drug interactions, unveiling distinct binding modes and hydrogen bonding patterns that shed light on how the solvatomorphic structure may impact drug-target interactions. In-depth molecular dynamics simulations over 100 ns investigate the stability of the protein-ligand complex, with root mean square deviation and root mean square fluctuation analyses revealing minimal deviations and affirming the stability of FAM within the active site of the target protein.

Role of Heteronucleants in Melt Crystallization of Crystalline Solid Dispersions

Few publications exist concerning polymorphic control during melt crystallization, particularly when employing heteronucleants. Here, the influence of a polymeric thin film (polyethylene terephthalate, PET) on the crystallization from melt of the polymorphic compound acetaminophen (ACM) in polyethylene glycol (PEG) was investigated. Molten ACM-PEG at different compositions was monitored using in situ Raman spectroscopy for nucleation induction time measurements and phase identification. Furthermore, X-ray diffraction (XRD) served to analyze the preferred orientation (PO) of the pastilles (solidified melt droplets) on PET-coated and uncoated substrates. The results indicate that PET-coated substrates qualitatively accelerate the nucleation of ACM form II (ACM II) in PEG compared to uncoated glass substrates. Additionally, the occurrence of ACM II in PEG was increased by an average of 10% when crystallized on PET-coated substrates compared to uncoated substrates. Overall, these results suggest that ACM can interact through hydrogen bonding with the PET-coated substrate, leading to faster nucleation. This investigation illustrates the effect of PET-coated substrates in the selective crystallization of ACM II in PEG as crystalline solid dispersions (CSDs). Ultimately, the results suggest the implementation of polymeric heteronucleants in melt crystallization processes, specifically, in advanced polymer-based formulation processes for the enhanced polymorphic form control of pharmaceutical compounds in CSDs.

Solvent-Mediated Polymorphic Transformations in Molten Polymers: The Account of Acetaminophen

Solvent-mediated polymorphic transformations (SMPTs) employing nonconventional solvents (polymer melts) is an underexplored research topic that limits the application of polymer-based formulation processes. Acetaminophen (ACM), a widely studied active pharmaceutical ingredient (API), is known to present SMPTs spontaneously (<30 s) in conventional solvents such as ethanol. In situ Raman spectroscopy was employed to monitor the induction time for the SMPT of ACM II to I in polyethylene glycol (PEG) melts of different molecular weights (Mw, 4000, 10 000, 20 000, 35 000 g/mol). The results presented here demonstrate that the induction time for the SMPT of ACM II to I in PEG melts is driven by its diffusivity through the polymer melts. Compared to conventional solvents (i.e., ethanol) the mass transfer (diffusion coefficient, D) in melts is significantly hindered (Dethanol = 4.84 × 10-9 m2/s > DPEGs = 5.32 × 10-11-8.36 × 10-14 m2/s). Ultimately, the study proves that the induction time for the SMPT can be tuned by understanding the dispersant's physicochemical properties (i.e., η) and, thus, the D of the solute in the dispersant. This allows one to kinetically access and stabilize metastable forms or delay their transformations under given process conditions.

Hydrogel with silver nanoparticles synthesized by Mimosa tenuiflora for second-degree burns treatment

In this work we use Mimosa tenuiflora (MtE) extracts as reducing agents to synthesize silver nanoparticles (AgMt NPs) which were characterized by DPPH and Total Polyphenols Assays, UV-visible, X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis (TGA). AgMt NPs possess average sizes of 21 nm and fcc crystalline structure, it was also confirmed that the MtE is present in the AgMt NPs even after the cleaning protocol applied. Subsequently, carbopol hydrogels were made and the MtE and the synthesized AgMt NPs were dispersed in different gels (MtE-G and AgMt NPs-G, respectively) at 100 µg/g concentration. The gels were characterized by UV-Vis, IR, and rheology. Antimicrobial tests were performed using Staphylococcus aureus and Escherichia coli. Burn wound healing was evaluated in a second-degree burn injury on a Wistar rats model for 14 days and additional skin biopsies were examined with histopathological analysis. Gel with commercial silver nanoparticles (Ag NPs) was prepared and employed as a control on the biological assays. Hydrogel system containing silver nanoparticles synthesized with Mimosa tenuiflora (AgMt NPs-G) is a promising therapeutic strategy for burn wound healing, this due to bactericidal and anti-inflammatory effects, which promotes a more effective recovery (in percentage terms) by damaged area.

Polymorphism in Solid Dispersions

Solid dispersions embed active pharmaceutical ingredients in polymeric carriers to improve their solubility. Three solid dispersion preparation techniques are typically employed: solvent evaporation, solvent-fusion, and fusion methods. Although these are also widely recommended as preparative methods for phase diagram determination, few examples exist concerning their effect on the resulting polymorph, once the solid dispersion is produced. In this study, the influence of these methods on the polymorphic form obtained in crystalline solid dispersions (CSDs) composed of flufenamic acid (FFA) and poly(ethylene glycol) was investigated. The physical mixtures and CSDs were characterized by powder X-ray diffraction, infrared spectroscopy, and differential scanning calorimetry. The results reveal that the fusion method leads to concomitant polymorphs (mainly FFA I and III) in the CSDs. In contrast, the solvent evaporation and solvent-fusion methods lead to FFA III. Collectively, these results demonstrate that preparative methods have a significant influence on the phase diagrams determined (average relative deviation ≤8%), which are often used to justify the design space of manufacturing processes, including those deemed "continuous." Consequently, choosing a preparation method that results in the desired polymorph is crucial to ensure accurate determination of phase diagrams and critical quality attributes of formulations.