Adhesion of pharmaceutical particles to gelatin capsules having variable surface physicochemical properties: evaluation using a combination of scanning probe microscopy techniques

The adhesion of particles to solid surfaces is an important factor in the performance of a number of technologically significant systems. A combination of scanning probe microscopy (SPM) techniques, including adhesion mapping and force integration to equal limits imaging, is used to correlate the adhesion of particles with areas of distinct surface physicochemical properties. The utility of this approach is demonstrated using lactose particles and a gelatin capsule from a pharmaceutical dry powder inhalant drug delivery system. The particle adhesion forces were found to be higher on specific domains of the gelatin capsule identified as extraneous surface contamination. Furthermore, the dynamic nature of these contaminant domains on the capsule surface was found to result in a variance in the particle adhesion over time.