Effects of mechanical impaction on aerosol performance of particles with different surface roughness

The effect of mechanical impaction on the aerosol performance of pharmaceutical powders comprising smooth and rough-surfaced spherical particles was investigated. Bovine serum albumin (BSA) was chosen as a model drug and powders prepared using spray drying. Surface roughness and adhesion force properties of BSA were measured by atomic force microscopy. The aerosol performance of the powders was assessed by impaction using a customised throat model built with specific mitre joints (0, 15, 45 and 90°), coupled with a liquid impinger through a laser diffractometer. Results showed enhanced aerosol performance of BSA by mechanical impaction, with the effect increasing with the impaction angle and being more pronounced with corrugated BSA. This is attributed to the lower cohesion force between the corrugated particles, enabling them to de-agglomerate more readily on impaction. In conclusion, impaction causes significantly better deagglomeration in corrugated particles than smooth particles. A combination of mechanical impaction and rough surface will help maximise the aerosol performance of powders for inhalation drug delivery.