New polymorphs of 9-nitro-camptothecin prepared using a supercritical anti-solvent process

Aluminum ion catalyzed proton transfer: Mechanism on promoting highly stable passivation of Cr by soil organic matter

Although biochar can passivate chromium (Cr3+) in soil, the low stability is still a challenge to be overcome since the passivation mechanism is dominated by weak interactions (complexation, electrostatic attraction, etc.). In this study, a highly stable passivation of Cr3+ was achieved in soil based on the strategy that the low-energy sp hybridisation orbitals of aluminum (Al3+) induced a decrease in the HOMO energy level, leading to the enrichment of off-domain electrons in carbon-based conjugated systems. It can promote the proton transfer and the ion exchange, facilitating the strong chemical binding of organic matter to Cr3+. It suggested that the introduction of Al3+ significantly enhanced the passivation efficiency, maintaining a growth over 42 days of aging. To achieving a high stable passivation, the key is promoting a higher proportion of organic matter-bound Cr3+ contributing by the introduction of Al3+. DFT calculations further validated thermodynamically that, only Al3+ had the catalytic effect on both proton transfer and Cr3+ passivation compared with K+, Na+, Ca2+, Mg2+, Fe3+, Zr4+. These findings can provide important insights for developing a new generation of passivators which can efficiently stabilize heavy metal.

Particle preparation of pharmaceutical compounds using supercritical antisolvent process: current status and future perspectives

The low aqueous solubility and subsequently slow dissolution rate, as well as the poor bioavailability of several active pharmaceutical ingredients (APIs), are major challenges in the pharmaceutical industry. In this review, the particle engineering approaches using supercritical carbon dioxide (SC CO₂) as an antisolvent are critically reviewed. The different SC CO₂-based antisolvent processes, such as the gas antisolvent process (GAS), supercritical antisolvent process (SAS), and a solution-enhanced dispersion system (SEDS), are described. The effect of process parameters such as temperature, pressure, solute concentration, nozzle diameter, SC CO₂ flow rate, solvent type, and solution flow rate on the average particle size, particle size distribution, and particle morphology is discussed from the fundamental perspective of the SAS process. The applications of the SAS process in different formulation approaches such as solid dispersion, polymorphs, cocrystallization, inclusion complexation, and encapsulation to enhance the dissolution rate, solubility, and bioavailability are critically reviewed. This review highlights some areas where the SAS process has not been adequately explored yet. This review will be helpful to researchers working in this area or planning to explore SAS process to particle engineering approaches to tackle the challenge of low solubility and subsequently slow dissolution rate and poor bioavailability.

Controlling the Polymorphism of Indomethacin with Poloxamer 407 in a Gas Antisolvent Crystallization Process

The polymorphic control of active pharmaceutical ingredients (APIs) is a major challenge in the manufacture of medicines. Crystallization methods that use supercritical carbon dioxide as an antisolvent can create unique solid forms of APIs, with a particular tendency to generate metastable polymorphic forms. In this work, the effects of processing conditions within a gas antisolvent (GAS) crystallization method, such as pressure, stirring rate, and temperature, as well as the type of solvent used and the presence of an additive, on the polymorphism of indomethacin were studied. Consistent formation of the X-ray powder diffraction-pure α polymorphic form of indomethacin by GAS was only achieved when a polymer, poloxamer 407, was used as an additive. Using the GAS method in combination with poloxamer 407 as a molecular additive enabled full control over the polymorphic form of indomethacin, regardless of the processing conditions employed, such as pressure, temperature, stirring rate, and type of solvent. A detailed molecular modeling study provided insight into the role of poloxamer 407 in the polymorphic outcome of indomethacin and concluded that it favored the formation of the α polymorph.

Pharmaceutical cocrystals, salts and polymorphs: Advanced characterization techniques

The main goal of a novel drug development is to obtain it with optimal physiochemical, pharmaceutical and biological properties. Pharmaceutical companies and scientists modify active pharmaceutical ingredients (APIs), which often are cocrystals, salts or carefully selected polymorphs, to improve the properties of a parent drug. To find the best form of a drug, various advanced characterization methods should be used. In this review, we have described such analytical methods, dedicated to solid drug forms. Thus, diffraction, spectroscopic, thermal and also pharmaceutical characterization methods are discussed. They all are necessary to study a solid API in its intrinsic complexity from bulk down to the molecular level, gain information on its structure, properties, purity and possible transformations, and make the characterization efficient, comprehensive and complete. Furthermore, these methods can be used to monitor and investigate physical processes, involved in the drug development, in situ and in real time. The main aim of this paper is to gather information on the current advancements in the analytical methods and highlight their pharmaceutical relevance.

Characterization of new crystalline forms of hydroxyprogesterone caproate

A systematic polymorph screening process was conducted on the steroid hydroxyprogesterone caproate, which had only one previously described orthorhombic crystalline form (A), in order to fully elucidate its solid state properties. Cooling, anti-solvent and evaporative techniques largely reproduced the same polymorph, but slurries in various solvents over two days produced a new triclinic form (B). Experiments at different temperatures in ethyl acetate or isopropyl alcohol confirmed this was an enantiotropic system with a transition temperature of approximately 30°C. DSC was used to confirm the transition of Form B to Form A below the melting point. Form B was the thermodynamically stable form at room temperature, and 8% less soluble in a non-aqueous solvent mixture. In viscous solvents used commercially to dissolve the oil-soluble steroid for injection, solutions near the solubility limit can remain supersaturated after exposure to cooler temperatures for months. In resolving the crystalline structure of Form A, a third conformational polymorph was detected that exists only at -133 to -143°C; this monoclinic form was designated Form C, and converts back to Form A upon warming to room temperature. These studies have increased the understanding of this drug and how the polymorphs may affect its physical stability in different dosage forms.