Polymeric particle formation through electrospraying at low atmospheric pressure.

Electrospraying is a simple and versatile technique capable of producing polymeric particles. However, most investigations carried out thus far have been performed at ambient atmospheric pressure without studying the influences of pressure on the formation of polymeric particles. Here, we report our investigation on the effects of varying the pressure and the solution concentration on the microstructures of electrosprayed polymeric particles. Pressures are varied from ambient atmospheric pressure to 380 mmHg below ambient pressure, and solution concentrations are varied over a range of 3-7 w/v %. By varying these parameters, we manipulated the rate of solvent evaporation and the solidification of the electrosprayed particles. The results show that changes to the pressure had significant effects on the microstructure and morphology of poly(epsilon-caprolactone) (PCL) particles. The average particle size became larger as the chamber pressure decreased. At a solution concentration of 5 w/v % and a pressure 150 mmHg below ambient pressure, uniform and spherical PCL particles were generated. Electrospun fibers were formed when a solution concentration of 7 w/v % was used. The developed technique can be applied to prepare polymeric drug delivery carriers though a low-pressure-assisted spray-drying method, and is particularly suitable for fabricating delivery microspheres encapsulated with temperature-sensitive drugs and biomolecules.