Preparation and characterization of surface-engineered coarse microcrystalline cellulose through dry coating with silica nanoparticles.

A popular grade of microcrystalline cellulose (MCC) exhibits excellent tabletability, but marginal flowability for high-speed tableting operations. Accordingly, an enhancement in flowability, while preserving its tabletability, will make it a more useful excipient in pharmaceutical tablet formulations, especially for the direct compression process. In this work, we show that surface coating by silica nanoparticles, using either a dry comilling process or simple mechanical blending, is a valid strategy for achieving the goal. The effects of milling intensity, either the number of comilling cycles or blending time, and silica loading level have been evaluated. Results show that surface deposition of 0.1% silica nanoparticles substantially improves the flowability of this grade of MCC while preserving a significant portion of its tabletability. Higher silica loading leads to better flowability, but at the cost of reduced tabletability. However, even up to 2.0% silica deposition, its tabletability remains superior.