Controlled nucleation of crystallization process as an efficient tool to tune the properties of corticosteroid API

Surface and Subsurface Mass Spectrometric Analysis of Dexamethasone in Solid Pharmaceutical Dosage Forms

This study presents an in-depth mass spectrometric investigation of dexamethasone (DEX) distribution within pharmaceutical tablets using time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with gas cluster ion beam (GCIB) sputtering. Fragmentation mechanism of DEX was identified, which enabled the determination of three-dimensional chemical imaging of the active ingredient in both surface and subsurface regions. The data reveal that a 4-mg DEX formulation exhibits a continuous and extended distribution of the drug into the tablet matrix, while a 0.5-mg formulation shows DEX localized in distinct, isolated domains. Topographical features and the overall composition of the surface were confirmed by complementary analyses employing atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). These results demonstrate how molecule distribution patterns can be linked to formulation heterogeneity using advanced mass spectrometric techniques, opening new possibilities for pharmaceutical manufacturing quality control and optimization.

Ultrasound induced grain refinement of crystallization in evaporative saline droplets

We investigate the effect of ultrasound on the evaporation and crystallization of sessile NaCl solution droplets which were positioned in traveling or standing wave ultrasound field. The experimental results indicated that the ultrasound field can significantly accelerate the evaporation rate of the sessile droplets and refine the crystal grains. By adjusting the distance between the sessile droplets and the ultrasound emitter, it is found that, in traveling wave ultrasound field, the sessile droplet evaporation time and the time for the appearance of NaCl grains exhibited a fluctuating increase as the droplet-emitter distance increased. While in the standing wave ultrasound, the sessile droplet evaporation rate increases with the increasing droplet-emitter distance. Overall, the traveling wave ultrasound field has a stronger effect on grain refinement of the sessile droplets than the standing wave ultrasound field. The grain refinement is attributed to the decrease of critical nucleation radius caused by ultrasound energy and the increase of the nucleation rate caused by the accelerated evaporation rate. In addition, the breakage of grains caused by ultrasonic cavitation would also lead to grain refinement.

Patterns during Evaporative Crystallization of a Saline Droplet

In the present work, we investigate the influence of substrate wettability and crystal morphology on the evaporative crystallization of saline droplets. On a superhydrophilic substrate, the evaporative crystals formed during the drying of a saline droplet of aqueous potassium nitrate are observed to be long and needle-shaped, oriented along the substrate. The crystal deposits form a flower-shaped pattern when the initial contact angle of the droplet increases to ∼72°. The orientation of the crystals along the triple contact line of the droplet controls the self-amplifying creeping growth of the salt crystals that eventually determines the overall evaporative patterns. The crystals change from being needle-shaped to globular salt deposits as the volume of liquid available for crystallization reduces. We demonstrate that the arrangement of the crystal with respect to the substrate and the droplet-air interface governs the rate of evaporation, growth, and morphology of the crystals.