Effective Control of Crystal Size via an Integrated Crystallization, Wet Milling, and Annealing Recirculation System

Growth of broken crystals tracked in 4D using X-ray computed tomography and its influence on impurity incorporation

Crystallization is a commonly used unit operation for separation and purification. During processing, crystals may break due to mechanical stress, e.g., intentionally by milling or unintentionally through collision with stirrers. This study investigates the growth of broken crystals in three dimensions using X-ray micro-computed tomography. The results show that damaged regions of crystals grow faster than faceted regions, and crystals become faceted through growth. Initially, this happens on a microscale, producing faceted but concave regions on the crystal surface. Eventually, crystals become convex. Shape-healing through growth incorporates inclusions in the crystals. These findings have important implications for designing and optimizing crystallization processes in the pharmaceutical, food, and chemical industries, as purity is often a critical quality criterion adversely affected by inclusions. In addition, the kinetics in crystallization processes are likely to be strongly affected by the growth of non-faceted and concave crystals.

Amelioration of tableting properties and dissolution rate of naproxen co-grinded with nicotinamide: preparation and characterization of co-grinded mixture

OBJECTIVE AND SIGNIFICANCE

Reducing the dimensions, when other additives are present, shows potential as a method to improve the dissolution and solubility of biopharmaceutical classification system class II drugs that have poor solubility. In this investigation, the process involved grinding naproxen with nicotinamide with the aim of improving solubility and the rate of dissolution.

METHODS

Naproxen was subjected to co-milling with urea, dimethylurea, and nicotinamide using a planetary ball mill for a duration of 90 min, maintaining a 1:1 molar ratio for the excipients (screening studies). The co-milled combinations, naproxen in its pure milled form, and a physical mixture were subjected to analysis using X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), and solubility assessment. The mixture displaying the highest solubility (naproxen-nicotinamide) was chosen for further investigation, involving testing for intrinsic dissolution rate (IDR) and Fourier-transform infrared spectroscopy (FTIR) after co-milling for both 90 and 480 min.

RESULTS AND CONCLUSION

The co-milled combination, denoted as S-3b and consisting of the most substantial ratio of nicotinamide to naproxen at 1:3, subjected to 480 min of milling, exhibited a remarkable 45-fold increase in solubility and a 9-fold increase in IDR. XRPD analysis of the co-milled samples demonstrated no amorphization, while SEM images portrayed the aggregates of naproxen with nicotinamide. FTIR outcomes negate the presence of any chemical interactions between the components. The co-milled sample exhibiting the highest solubility and IDR was used to create a tablet, which was then subjected to comprehensive evaluation for standard attributes. The results revealed improved compressibility and dissolution properties.

Reactive crystallization: a review

Reactive crystallization is not new, but there has been recent growth in its use as a means of improving performance and sustainability of industrial processes.