Direct evidence on reduced adhesion of Salbutamol sulphate particles due to L-leucine coating

Attractive van der Waals forces are responsible for unwanted agglomeration of fine dry powder particles which can cause problems e.g. with inhalable drugs in the treatment of asthma. In this article we report on experimental evidence of reduced adhesion of salbutamol sulphate particles when they are coated with L-leucine. Particle production and coating was performed using an aerosol flow reactor. The L-leucine-containing particles were fully covered with L-leucine as evidenced by X-Ray Photoelectron Spectroscopy and Scanning Electron Microscopy findings. With a suitable concentration of precursor solution the particles become rough and adhesion diminished to one fifth of the adhesion of uncoated particles. The main reason for this reduced adhesion was an increase in surface roughness, which reduced the contact area and the number of contact points thus increasing the effective separation between particles.