Model-based Design of Shear-Induced Thin Film Nanosmears Influencing Tribological Properties of Pharmaceutical Powders

C.F. Kick, K.C. Pingali
Western Michigan University, US

Keywords: nanosmearing, process shear, mixing, X-ray energy dispersive spectroscopy, inductively coupled plasma mass spectroscopy

Summary:

The pharmaceutical industry faces the challenge of understanding how tribological particle behavior during mixing influences scale up performance of tableted solid dosage forms. During batch processing, changes in surface chemistry as a result of mixing order, shear, and flowing agent concentration can consequently alter the intended functionality of ingredients in the powder. Preliminary results show the extent and thickness of the nanosmear layer significantly influences critical blend properties in the powder and the efficacy of dissolution in the tablets. This identifies that key characteristics of the nanosmear layer including the extent, chemical composition, and thickness are poorly understood. This study has identified differences in rate of formation of nanostructures due to process shear for various mixing orders of the pharmaceutical flowing agents Magnesium Stearate and Cab-O-Sil. Micro characterization techniques using FESEM with Xray-EDS mapping provided electron density maps from which the extent of the thin film nanosmears could be characterized. Quantification of the nanosmears was assessed utilizing Inductively Coupled Plasma Mass Spectroscopy (ICPMS). The experimental data will aid in the development of a deterministic model for predicting smearing indices in pharmaceutical blends. This model is intended to prevent over-lubrication and product batch failures from blends that don’t meet performance standards.