Crystal Structure and Morphology of Adipic Acid/PVP Particles Formed Via Monodisperse Droplet Evaporation

Crystal Structure and Morphology of Adipic Acid/PVP Particles Formed via Monodisperse Droplet Evaporation

Tara L. Panzarino

Advisor: Ryan C. Snyder

Bucknell University, Department of Chemical Engineering

Particle characteristics and formation play a large role in the pharmaceutical industry.  The characteristics of the particle determine the effectiveness and quality of the final drug product.  In particular, the degree of crystallinity of the active pharmaceutical ingredients (APIs) can impact the dissolution and bioavailability of the API. Amorphous particles are desirable because they have higher solubility than any of the crystalline forms; however they are not always easy to produce.  The goal of this work is to obtain amorphous particles of adipic acid, with the addition of an excipient. The resulting particles are compared to the morphology and crystallinity of particles formed only with adipic acid.  In this work, the primary excipient considered is Polyvinylpyrrolidone (PVP). Particles of adipic acid and PVP are formed from the evaporation of monodisperse droplets produced from a Vibrating Orifice Aerosol Generator (VOAG). The VOAG creates monodispersed particles by applying a constant frequency across a solution jet to create droplets. These droplets are then allowed to dry in a column, and the particles can be collected and analyzed.

Solutions of varying weight % ratios of adipic acid and PVP in isopropanol were considered. Particles of Adipic Acid and PVP were analyzed for structure using X-ray Diffraction. The results show that as the ratio of Adipic Acid to PVP became smaller, the particles became less crystalline in nature, with a transition around 50 weight % of each component. Morphology is also analyzed with SEM imaging. The morphology changes such that as the weight % ratio of Adipic Acid decreased, the particles became increasingly smooth. Adipic Acid particles ran through the VOAG in solutions of isopropanol typically have a wrinkled appearance, with a hole somewhere on the particle. Future plans also are presented.