New Development in Understanding Drug-Polymer Interactions in Pharmaceutical Amorphous Solid Dispersions from Solid-State Nuclear Magnetic Resonance

Comparative properties of ZnO modified Au/Fe nanocomposite: electronic, dynamic, and locator annealing investigation

CONTEXT

A computational representation was used to model the doping and nanomodification of ZnO nanoparticles incorporated in Au/Fe nanocomposite. Au/Fe nanostructure was geometrically and discussed to investigate its electronic properties such electronic band structure and PDOS spectra. Moreover, the ZnO interacted with Au/Fe system was illustrated concerning the modified properties present on the surface of the nanocomposite as it may behave different attribution of band gap evaluated after ZnO modification included. Molecular dynamic simulation of the whole nano system was studied to predict the system stability concerning temperature and energy parameters during 100 ps simulation time. The most effective models under investigation were evaluated using adsorption annealing computations associated with the adsorption energy surface. A highly stable energetic adsorption system was anticipated by the periodic adsorption-annealing calculation.

METHODS

Au and Fe pure metals nanostructures were studied as a separate molecule with (0 0 1) plane surface for optimum energy minimization. Dmol3 module in/materials studio software was utilized for this protocol. The designed Au/Fe layers for nanostructure building material was computationally optimized, where DFT level was considered involving generalized gradient approximation (GGA) with Perdew-Burke-Ernzerh (PBE) exchange functional. In the computations of the structure matrix simulation, the global orbital cutoff was selected. To address the weak quantification of the standard DFT functionals, Tkatchenko-Schefer (TS) (DFT + D) was utilized to precisely correct the pairwise dispersion of the functionals. The electrical parameters were interpreted using the reciprocal space of the ultrasoft pseudopotential representation. To overcome the issues of self-electron interaction, the nonlocal hybrid functional with PBE0 method was utilized to calculate the electronic properties of the studied systems. The computations generated are predicated on a particular trajectory of the gamma k-point band energy interpolations proposed in this examination. An investigation into the position of adsorption came after geometric optimization. Adsorbed on an optimized Au/Fe surface, ZnO nanostructure was computationally explored using the Dmol3 simulation software.

Overcoming drug impurity challenges in amorphous solid dispersion with rational development of biorelevant dissolution-permeation method

Hot-melt extrusion is often used to prepare amorphous solid dispersion to overcome low drug solubility and enhance bio-performance of the formulation. Due to the uniqueness of each drug - polymer combination and its physico-chemical properties, setting the appropriate HME barrel temperature, feed rate and screw speed ensures drug amorphization, absence of residual crystallinity, absence of water, and a suitable drug release profile. In this research, samples with BCS II/IV model drug and PVP/VA polymer were prepared to evaluate the impact of HME process parameters, incoming drug form (anhydrous vs. hydrate), and drug supplier (i.e., impurity profile), on biorelevant drug release. This study provides a relationship between observed in vitro supersaturation and precipitation behavior of amorphous solid dispersion formulation with in vivo results, on patients, by using the acceptor profile of side-by-side dissolution-permeation apparatus. An in vitro dissolution method, in small volumes, in an apparatus with paddles and dissolution-permeation side-by-side method was developed on the MicroFlux™ apparatus to assess if the differences observed in vitro bears relevance to the bioequivalence outcome in vivo. The former was used to guide the generic drug product development due to high discriminatory strength, while the latter was biorelevant, due to the inclusion of the second compartment assuring absorptive environment to capture the impact of supersaturation and subsequent precipitation on bioavailability. Bio-relevancy of the in vitro method was confirmed with the in vivo dog study and clinical study on patients, and an in vitro - in vivo correlation was established. For the investigated BCS II/IV drug, this research highlights the importance of considering supersaturation and formation of colloidal species during amorphous solid dispersion release testing to assure product quality, safety and efficacy.

Improvement in Inhalation Properties of Theophylline and Levofloxacin by Co-Amorphization and Enhancement in Its Stability by Addition of Amino Acid as a Third Component

Co-amorphous systems are amorphous formulations stabilized by the miscible dispersion of small molecules. This study aimed to design a stable co-amorphous system for the co-delivery of two drugs to the lungs as an inhaled formulation. Theophylline (THE) and levofloxacin (LEV) were used as model drugs for treating lung infection with inflammation. Leucine (LEU) or tryptophan (TRP) was employed as the third component to improve the inhalation properties. The co-amorphous system containing THE and LEV in an equal molar ratio was successfully prepared via spray drying where reduction of the particle size and change to the spherical morphology were observed. The addition of LEU or TRP at a one-tenth molar ratio to THE-LEV did not affect the formation of the co-amorphous system, but only TRP acted as an antiplasticizer. The Fourier transform infrared spectroscopy spectra revealed intermolecular interactions between THE and LEV in the co-amorphous system that were retained after the addition of LEU or TRP. The co-amorphous THE-LEV system exhibited better in vitro aerodynamic performance than a physical mixture of these compounds and permitted the simultaneous delivery of both drugs in various stages. The co-amorphous THE-LEV system crystallized at 40 °C, and this crystallization was not prevented by LEU. However, THE-LEV-TRP maintained its amorphous state for 1 month. Thus, TRP can act as a third component to improve the physical stability of the co-amorphous THE-LEV system, while maintaining the enhanced aerodynamic properties.

Polymer-inducing chemical degradation of amorphous solid dispersions driven by drug-polymer interactions for physical stabilization

Intermolecular interactions between active pharmaceutical ingredients (APIs) and carrier polymers are important for the long-term physical stability of amorphous solid dispersions (ASDs). However, the negative impact of intermolecular interactions on chemical stability has rarely been reported. In this study, the relationship between intermolecular interactions and physical and chemical stability was investigated using two ASDs composed of API and hydroxypropyl methylcellulose acetate succinate (HPMCAS) with different stabilities: ASD1 was physically stable but chemically unstable, whereas ASD2 was physically unstable but chemically stable. Ionic-bonding between the pyridine nitrogen in the API and succinyl group in HPMCAS was found in both ASDs. The additional interaction between the succinyl group in HPMCAS and the hydroxyl group in the API was suggested only in ASD1. It was concluded that the additional interaction contributed to the physical stability of ASD1; however, it accelerated the chemical reaction between the succinyl and hydroxyl groups to generate succinyl ester owing to its close proximity. This study shows that the intermolecular interaction between the API and carrier polymer is not always beneficial for chemical stability. Understanding the molecular states of APIs and polymers in ASDs is important for their successful development.

Probing Molecular Packing of Amorphous Pharmaceutical Solids Using X-ray Atomic Pair Distribution Function and Solid-State NMR

The structural investigation of amorphous pharmaceuticals is of paramount importance in comprehending their physicochemical stability. However, it has remained a relatively underexplored realm primarily due to the limited availability of high-resolution analytical tools. In this study, we utilized the combined power of X-ray pair distribution functions (PDFs) and solid-state nuclear magnetic resonance (ssNMR) techniques to probe the molecular packing of amorphous posaconazole and its amorphous solid dispersion at the molecular level. Leveraging synchrotron X-ray PDF data and employing the empirical potential structure refinement (EPSR) methodology, we unraveled the existence of a rigid conformation and discerned short-range intermolecular C-F contacts within amorphous posaconazole. Encouragingly, our ssNMR 19F-13C distance measurements offered corroborative evidence supporting these findings. Furthermore, employing principal component analysis on the X-ray PDF and ssNMR data sets enabled us to gain invaluable insights into the chemical nature of the intermolecular interactions governing the drug-polymer interplay. These outcomes not only furnish crucial structural insights facilitating the comprehension of the underlying mechanisms governing the physicochemical stability but also underscore the efficacy of synergistically harnessing X-ray PDF and ssNMR techniques, complemented by robust modeling strategies, to achieve a high-resolution exploration of amorphous structures.

Enhanced Oral Bioavailability of Rivaroxaban-Loaded Microspheres by Optimizing the Polymer and Surfactant Based on Molecular Interaction Mechanisms

This study aimed to develop microspheres using water-soluble carriers and surfactants to improve the solubility, dissolution, and oral bioavailability of rivaroxaban (RXB). RXB-loaded microspheres with optimal carrier (poly(vinylpyrrolidone) K30, PVP) and surfactant (sodium lauryl sulfate (SLS)) ratios were prepared. 1H NMR and Fourier transform infrared (FTIR) analyses showed that drug-excipient and excipient-excipient interactions affected RXB solubility, dissolution, and oral absorption. Therefore, molecular interactions between RXB, PVP, and SLS played an important role in improving RXB solubility, dissolution, and oral bioavailability. Formulations IV and VIII, containing optimized RXB/PVP/SLS ratios (1:0.25:2 and 1:1:2, w/w/w), had significantly improved solubility by approximately 160- and 86-fold, respectively, compared to RXB powder, with the final dissolution rates improved by approximately 4.5- and 3.4-fold, respectively, compared to those of RXB powder at 120 min. Moreover, the oral bioavailability of RXB was improved by 2.4- and 1.7-fold, respectively, compared to that of RXB powder. Formulation IV showed the highest improvement in oral bioavailability compared to RXB powder (AUC, 2400.8 ± 237.1 vs 1002.0 ± 82.3 h·ng/mL). Finally, the microspheres developed in this study successfully improved the solubility, dissolution rate, and bioavailability of RXB, suggesting that formulation optimization with the optimal drug-to-excipient ratio can lead to successful formulation development.

Electronic band structure and density of state modulation of amphetamine and ABW type-zeolite adsorption system: DFT-CASTEP analysis

The structured abstract is combined from two parts: CONTEXT: The adsorption behavior of amphetamine (AMP) on the surface of ABW-aluminum silicate zeolite was implemented with a computational depiction. Studies of the electronic band structure (EBS) and density of states (DOS) were conducted to demonstrate transition behavior attributed to aggregate-adsorption interaction. Thermodynamic illustration of the studied adsorbate was studied to investigate the structural behavior of the adsorbate on the surface of the zeolite adsorbent. The best investigated models were assessed with adsorption annealing calculations related to adsorption energy surface. The periodic adsorption-annealing calculation model predicted a highly stable energetic adsorption system based on total energy, adsorption energy, rigid adsorption energy, deformation energy, and dE_ad/d_Ni ratio. METHODS: Cambridge sequential total energy package (CASTEP) based on density functional theory (DFT), under Perdew-Burke-Ernzerhof (PBE) basis set, was used to depict the energetic levels of the adsorption mechanism between AMP and ABW-aluminum silicate zeolite surface. DFT-D dispersion correction function was postulated for weakly interacted systems. Structural and electronic elucidations were described with geometrical optimization, FMOs, and MEP analyses. Thermodynamic parameters such as entropy, enthalpy, Gibbs free energy, and heat capacity over temperature dependence studied the conductivity behavior over localized energetic states based on Fermi level and described the disorder degree of the system.

Solid-state properties of Nifurtimox. Preparation, analytical characterization, and stability of an amorphous phase

Nifurtimox (NFX) is a nitrofuran derivative used to treat Chagas disease, a neglected disease caused by the protozoan Trypanosoma cruzi. The drug is very sparingly soluble in aqueous media and no other solid phases of NFX have been reported to date. The preparation of the amorphous mode of NFX is reported, as well as its characterization by hot stage microscopy, thermal (differential scanning calorimetry and thermogravimetric analysis), spectroscopic (solid state nuclear magnetic resonance, mid-infrared, and near-infrared), diffractometric and functional (powder dissolution rate) means. The stability of the new phase was investigated. This was characterized using thermal, spectroscopic, and diffractometric methods, finding out its spontaneous reversion to the crystalline state, as sign of instability. In addition, the amorphous material proved to be sensitive to temperature, pressure, and mechanical stress, all of which accelerated phase conversion. However, it was able to remain stable in a model polymeric amorphous solid dispersion with PEG 4000 for more than one month. An approach for monitoring the conversion of the amorphous phase to its crystalline counterpart under thermal stress by chemometric analysis of mid-infrared spectra at different temperatures is also disclosed.

Liquid-liquid phase separation drug aggregate: Merit for oral delivery of amorphous solid dispersions

As a promising strategy, amorphous solid dispersion has been extensively employed in improving the oral bioavailability of insoluble drugs. Despite the numerous advantages, the problems associated with supersaturation stability limit its further application. Recently, the formation and stability of the liquid-liquid phase separation drug aggregate (LLPS-DA) have been found to be vital for supersaturation maintenance. An in-depth review of LLPS-DA was required to further explore the supersaturation maintenance mechanism in vivo. Hence, this study aimed to present a short review to introduce the LLPS-DA, highlight the in vivo advantages for oral administration, and discuss the prospects to help understand the in vivo behavior of LLPS-DA.