Chitosan nano-spheres production by electrostatic emulsification technique

Electrostatic emulsification of an acidic chitosan solution into an organic solvent was examined for chitosan sphere production of controlled size ranging from nano to submicron scale. Droplets formation by the electrostatic emulsification was observed with a charge-coupled device camera. The diameters of generated water in oil emulsion droplets were measured by dynamic light scattering. At voltages greater than critical voltage, over which the electrostatic emulsification occurs, the droplet diameter "D" depended on the applied voltage "U", the electrode distance "L", and the flow rate of aqueous phase "F". An empirical formula for the relationship between the "D" and "U", "L" and "F" was obtained as Dâ̂U ^-0.65L ^0.43F ^0.14. Further, the chitosan spheres were obtained by cross-linking the emulsion droplets with glutaraldehyde, and were observed by using a scanning electron microscope. The chitosan nano-spheres of the size equal to the emulsion droplet were successfully obtained by the cross-linking of the chitosan and controlling a specific gravity difference of dispersed phase and continuous phase. These results show that the electrostatic emulsification is an excellent technique for the preparation of functional particles of controlled size ranging from nano to submicron scale.