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Updated: May 31, 2026

Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers
Published on: June 20, 2019
Polymer-mediated anti-solvent crystallization of nitrendipine: monodispersed spherical crystals and growth mechanism
Dengning Xia1, Mei Ouyang, Jian X Wu
1Department of Pharmaceutics, School of Pharmaceutical Science, Shenyang Pharmaceutical University, No. 103, Wenhua Road, Shenyang 110016, China.
Purpose:
To investigate anti-solvent crystallization and growth mechanism of nitrendipine spherical crystals in an aqueous solution containing polymeric additives.
Methods:
Size and shape of crystals were investigated using laser diffractometry, optical microscopy and scanning electron microscopy (SEM). Crystalline form was determined by X-ray powder diffractometer (XRPD). During crystal growth, morphological changes at different time points were observed using SEM.
Results:
Morphology of nitrendipine crystals was affected by polymers and temperature. Monodispersed micro-spherical crystals were obtained when polyvinyl alcohol (PVA) and PEG 200 were present in crystallization medium at 2°C. During crystallization, large number of amorphous nanoparticles was first observed, followed by aggregation into a core for spherical crystals. Once crystalline state was achieved, rapid growth on core surface was observed with amorphous particles acting as a reservoir allowing formation of star-like particles with needle-like subunits. Spherical crystals were formed by filling the gap between needle-like distinct crystalline units of star-like templates with molecules from dissolved amorphous particles.
Conclusions:
Monodispersed nitrendipine spherical crystals were obtained using carefully controlled conditions. A mechanism for the nitrendipine spherical crystal growth is suggested. These findings provide a new insight into spherulitic crystallization of active pharmaceutical ingredients.
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