Influences of process and formulation parameters on powder flow properties and immunogenicity of spray dried polymer...

Particle size, antigen load and its release characteristic are the three the main attributes of polymer particles based vaccine delivery systems. The present studies focus on the formulation of spray dried polylactide microparticles entrapping pneumococcal surface protein A (PspA). Influence of process variables during polymer particle formation were optimized by using half-factorial design. Feed rate and atomization pressure during spray drying were found to be the most important parameters for achieving uniform size particles. Spray drying of preformed particles from different stages of solvent evaporation method resulted in formation of particle having different porosity and protein release profile. Presence of polyvinyl alcohol in the external aqueous phase not only contributed towards regulating the size of particles but also influenced the burst release of protein from particles. Polymer particles entrapping PspA elicited robust IgG responses both in mice and in rats. Antigen load in microparticles correlated with the antibody titer indicating the maintenance of protein integrity during particle formation using spray drying. Both, process engineering and formulation parameters during spray drying influenced the particles in terms of size, load and antigen release characteristics.