A novel preparation method for drug nanocrystals and characterization by ultrasonic spray assisted electrostatic adsorption

Bing Gao,^1–3 Jun Wang,² Dunju Wang,^1,2 Ziqiang Zhu,^1,2 Zhiqiang Qiao,² Guangcheng Yang,² Fude Nie<sup>2

1</sup>School of Material Science and Engineering, Southwest University of Science and Technology, Mianyang, People's Republic of China, ²Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang, Sichuan, People's Republic of China, ³Si Chuan Research Center of New Materials, Mianyang, People's Republic of China

Purpose: The purpose of this study was to develop a novel and continuous method for preparing a nanosized particle of drug crystals and to characterize its properties.
Materials and methods: A new apparatus was introduced to crystallize nanosized drug crystals of amitriptyline hydrochloride as a model drug. The samples were prepared in the pure state by ultrasonic spray, and elaborated deposition was completed via electrostatic adsorption. Scanning electron microscopy, X-ray powder diffraction, and atomic force microscopy were used to characterize the size of the particles; this was subsequently followed by differential scanning calorimetry.
Results and discussion: Nanoparticles of drug crystals were successfully prepared. The size of the drug crystals ranged from 20 nm to 400 nm; the particle size of amitriptyline hydrochloride was approximately 71 nm. The particles were spherical and rectangular in shape. Moreover, the melting point of the nanoparticles decreased from 198.2°C to 196.3°C when compared to raw particle crystals. Furthermore, the agglomeration effect was also attenuated as a result of electrostatic repulsion among each particle when absorbed, and depositing on the inner wall of the gathering unit occurred under the electrostatic effect.
Conclusion: Ultrasonic spray-assisted electrostatic adsorption is a very effective and continuous method to produce drug nanocrystals. This method can be applied to poorly water-soluble drugs, and it can also be a very effective alternative for industrial production. Once the working parameters are given, drug nanocrystals will be produced continuously.

Keywords: nanomedicine, amitriptyline hydrochloride, continuous, nanoparticles