The ability to measure particle/particle interactions in pressurized metered dose inhaler (pMDI) propellants is central to excipient screening of suspension based pMDI formulations. Colloidal Probe Microscopy (CPM) is a variation of Atomic Force Microscopy (AFM) used to measure the interaction forces between a colloidal particle attached to an AFM tip and another particle/substrate. CPM is especially suited for the quantification of the adhesive/cohesive forces between particles and therefore can be employed in the screening of excipients and the study of surface property modifications and novel particle technologies. Moreover, CPM assessments can allow one to decouple confounding information regarding the physical stability of the dispersion and the aerosol characteristics of the corresponding formulation, which may be affected by the device components and other formulation parameters.
Atomic force microscopy (AFM): A quantitative tool for excipient screening of pMDI formulations
AFM and CPM (colloidal probe microscopy) can decouple confounding information on physical stability and aerosolcharacteristics of pMDI suspension formulations.