In situ observation on particle formation process via single droplet drying apparatus: Effects of precursor composition on particle morphology

Eudragit (R) RS 30D/silica composite precursor containing either Rhodamine B or sucrose as model drug was dried in a single droplet drying apparatus. Microparticles with distinct core-shell structure were produced by one-step drying for all compositions, while Rhodamine B showed uneven distribution in core and shell regions. At 5% (w/w) loading, it influenced shell formation process by producing dispersible initial shell and altered particle surface morphology into wrinkling appearance, while similar effects were not observed for sucrose. Decreasing the loading to 0.017% reduced the influence. The observations might be attributed to the properties of Rhodamine B, which affect its migration behavior during drying.