Porous hollow fiber membrane-based continuous technique of polymer coating on submicron and nanoparticles via antisolvent crystallization

This paper introduces a facile antisolvent crystallization technique to continuously coat submicron and nanosized particles with a thin polymer layer using a porous hollow fiber membrane device. Submicron (550 nm) and nanosized (12 nm) silica particles were the host particles; Eudragit RL 100 and poly(lactide-co-glycolide) were the coating polymers. A suspension of the particles in an acetone solution of the polymer was continuously pumped through the shell-side of a hollow fiber membrane module. The antisolvent (water) flowing in the hollow fiber lumen was forced through the membrane pores into the shell-side liquid, generating intense mixing with the flowing suspension and rapid precipitation of the polymer, coating the particles. Coated silica particles collected in a vacuum filtration device were analyzed after vacuum drying using scanning electron microscopy, scanning transmission electron microscopy, energy dispersive spectrometry, laser diffraction spectroscopy, and thermogravimetric analysis. These results indicate that a thin polymer coating of the submicron particles and nanoparticles of silica can be developed by this novel antisolvent crystallization technique using two widely different polymers. This continuous method is amenable to convenient scale-up.