The release of macromolecules from fatty acid matrices: complete factorial study of factors affecting release

A replicated complete factorial design to study the main effects and interactions of four factors: bovine serum albumin (BSA) particle size (Factor A); stearic acid particle size (Factor B); BSA loading (Factor C); and compression force (Factor D), on the release of BSA from compressed stearic acid pellets was performed in isotonic phosphate buffer pH 7.4 at 37 degrees C. Samples were withdrawn over 64 h. Analysis of variance of the percentage released at 64 h showed that A, B, and C, but not D, affected the release and the interactions AB, BC, ABC were highly significant. At low loading (5%), the surface release depended on BSA particle size. The release increased when BSA particle size was large. At high loading (20%), more release was shown when stearic acid particle size was large. More release with increasing BSA particle size occurred only when stearic acid particle size was small. It is proposed that release is due to the interconnected pore networks created, not only by BSA particles, but also by the void space between stearic acid particles. These void spaces vary according to particle size-dependent arrangements of stearic acid and BSA particles. An increase in the pellet thickness was observed probably due to the relaxation of compacted stearic acid particles.