Fundamental evaluation and optimization of porous spherical silica for developing functional fine particles via fluidized bed coating.

Particle coating, a taste-masking technique for drugs, is limited by its long manufacturing time, which is caused by the decrease in the spray rate required to prevent particle agglomeration. Mesoporous silica particles, which have a high surface area and pore sizes in the range of 2-50 nm, possess high surface free energy; they have attracted significant interest for numerous applications in adsorption, separation, and catalysis and drug delivery. A form of mesoporous silica, microbead silicate, can prevent particle aggregation because of its good water absorbency and drying properties. Hence, it has been suggested to be applicable for particle coating. This study evaluated the physical properties and drug release capability of microbead silicate with different pore sizes. Although microbead silicate with small pores displayed a rapid drug release profile, drug release was incomplete. Contrastingly, microbead silicate with large pores achieved complete drug release even with high drug loading. Furthermore, in the case of 100% layering, the porosity of microbead silicate was maintained, thus sufficiently preventing aggregation due to the prevention of formation of liquid bridging of the coating solution. These results suggest that using microbead silicate with large pores for particle coating enables complete drug release while improving manufacturability.