Preparation and characterization of magmatic polystyrene microspheres by means of a multiple emulsion technique.

Abstract

Magmatic microspheres find various applications in medicine and biotechnology as magneto-steerable drug carriers and in the separation and isolation of biological objects, among others. The advantage of using magmatic particles for this type of separation consists in reducing the time spent on them and in the ease of their isolation by means of a magnet once the process is finished. A method for obtaining magmatic polystyrene microspheres using a multiple water-in-oil-in-water emulsion is presented. In this method the internal aqueous phase consists of a colloidal dispersion of superparamagnetic magnetite particles; the oily phase is composed of polystyrene dissolved in dichloromethane and the external aqueous phase is a solution of polyvinyl alcohol in water. It is evident that the production conditions such as the concentration of magnetite in the internal aqueous phase and the amount of volatile solvent in the phase oleosa have a marked influence on the encapsulation efficiency and the dimensions of the microspheres. The polystyrene microspheres obtained contain the magnetite dispersed within the polymer matrix, so they retain their superparamagnetic character. Calculations based on the initial magnetization curve indicate that the magnetite particles contained in the microspheres have an average size similar to that of the starting ferrofluid (Do = 6.4 nm).