The influence of drug morphology on the aerosolisation efficiency of dry powder inhaler formulations

The physicochemical properties of two forms of spray dried bovine serum albumin (BSA) have been investigated using particle sizing, surface energy measurement, atomic force microscopy (AFM) and colloid probe microscopy. The BSA powder had similar particle size distributions and surface energy but significantly different morphologies and roughness, classified as smooth and corrugated BSA. Adhesion forces between the corrugated BSA and α-lactose monohydrate indicated median adhesion forces were significantly less than for smooth/carrier interaction forces. These observations correlated well with aerosolisation from BSA/carrier blends, where the corrugated BSA particles gave a higher fine particle fraction than the smooth BSA, suggesting reduced BSA/carrier adhesion and increased drug liberation. The use of corrugated drug particle morphology in drug carrier DPI systems may lead to improved aerosol performance through reduced drug carrier contact area.