(748c) Design and Analysis of a Modified Electrospray Process for Fabricating Polymeric Nano- and Microparticles for Drug Encapsulation

Rezvanpour, A., National University of Singapore
Krantz, W. B., University of Colorado
Wang, C., National University of Singapore

Electrohydrodynamic Atomization (EHDA), also referred to as the electrospray process, has been recently developed to fabricate polymeric micro- or nano-particles as well as fibers for drug encapsulation. EHDA in the cone-jet mode can produce highly monodisperse aerosols. As a result of strong electric forces, liquid droplets can be created by the electrospray process and converted into solid particles. In this study EHDA was carried out in a glass encapsulation chamber in which solid pharmaceutical particles were fabricated after evaporating the solvent from sprayed droplets. A high voltage nozzle with a concentric ring and a grounded collection plate were enclosed in an EHDA encapsulation chamber. A modified design for the encapsulation chamber was used in this study in which the particles are collected inside the chamber. Three major improvements were made in this modified design relative to prior art. First, the modified chamber is completely cylindrical whereas prior designs had two conical ends. Second, the particles fabricated in this modified chamber are collected inside the vessel far away from the spray zone. Finally, the nitrogen inlet and outlet in the modified chamber have larger diameters than earlier designs. Less reverse flow, higher particle collection efficiency and a lower amount of residual organic solvent in the collected particles are the main advantages of the aforementioned modifications.

The effects of different parameters on the particle collection efficiency were experimentally investigated. Important factors affecting the particle collection efficiency were the flow rate of the liquid solution used to create the particles, the nitrogen flow rate and the nozzle voltage. Systematic scaling analysis of the describing equations for the electrospray process permitted collapsing all the collection efficiency data onto a universal plot as a function of only one dimensionless group that incorporates all the process parameters. This plot can be used to determine the effect on the collection efficiency of changing the liquid solution flow rate, nitrogen flow rate and nozzle voltage as well as geometrical parameters such as length and diameter of the chamber, and location of the collection plate.