Development of highly porous microparticles from poly(ether imide) prepared by a spraying/coagulation process

Apheresis is an emerging technique to separate blood components from whole blood or plasma to remove pathologically elevated levels of proteins or toxins. Advantageously, the realization of apheresis by chromatographic techniques allows a selective or specific removal of blood components causing the disease. However, the particulate support material carrying the ligands is frequently not adapted to the necessities of large-volume, high molecular weight components, which have to be removed. Thus commercial support materials have the disadvantages of a too low accessibility of the internal pore system, a too poor flow-through behavior and/or a too high unspecific protein adsorption. Hence, novel support materials with optimally adapted properties profile have to be developed. Polyimides have been identified as novel blood compatible, steam-sterilizable materials that can be easily functionalized by wet-chemistry means. So far no suitable preparation process for the fabrication of highly porous beads is known. In this work, a novel support for apheresis application is presented which is based on microporous particles that were prepared from poly(ether imide) by a spraying/coagulation process. The polymer solution is sprayed through a hollow needle to form droplets and the droplets were vitrified by a nonsolvent induced phase separation. Results of the investigation of the spraying step and of the phase inversion step as well as characteristic data of the prepared particles are presented. Data of the particle characteristics verify that this technique is suitable to prepare highly porous support particles, which have a high accessibility of their internal pore system.