(68c) The  Role of Surface Energy on Developing Engineered Excipients during Dry Coating Process

Excipients with good flowability, bulk density as well as compaction properties are desired for use in tableting since they play important roles in formulation development and processing, including, handling, mixing, feeding and compaction. The objective of this work is to examine the feasibility of using dry coating based surface modification of microcrystalline cellulose, Avicel PH-105, to produce an engineered fine grade (particle size < 30μm) excipient that has all three desired properties. Using a material sparing, model based dry coating methodology, as-received grades of MCC were dry coated with 1wt% silica R972P, Aerosil 200 and M-5P. The results indicate that as expected, the bulk density and flowability of dry coated MCCs were significantly improved, while there was an appreciable loss of compaction. To understand the loss of compaction, the surface energy of the three grades silica and dry coated products were measured by using inverse gas chromatography. The results show that the loss in compaction is related to the reduced dispersive surface energy of the dry coated powders. Remarkably, use of Aerosil 200 led to a minimal reduction in compaction among these three grades of silica due to its highest dispersive surface energy among the selected silicas. This study shows that a new high functional grade of fine excipient which has a good flowability, bulk density and excellent compaction property was successfully developed. Moreover, surface energy can be a useful tool to predict whether a material can be good candidate for related studies in future.