A simple method for the preparation of monodisperse protein-loaded microspheres with high encapsulation efficiencies

A simple method for the preparation of monodisperse protein-loaded polymer microspheres is presented in this paper. The method is based on the co-extrusion of an internal phase of an aqueous protein solution and an external phase of an organic polymer solution through a 200-micron-sized hole. Controlled in the correct flow region, this process produces a core-shell-structured laminar liquid jet, which breaks to form monodisperse compound liquid droplets. Stabilized in a dilute aqueous polyvinyl alcohol (PVA) solution, the droplets are converted into solid protein-loaded polymer microspheres through evaporation of the organic solvent. Results show that preparation parameters such as polymer concentration, total flow rate, flow rate ratio of the aqueous to organic phase have significant effects on the mean particle size, particle morphology and protein encapsulation efficiency (EE). The results of biodegradation and the protein release characteristics of the polymer microspheres are also presented.