Temperature cycling-induced formation of crystalline coatings

The surface of particles is the hotspot of interaction with their environment and is therefore a major target forparticle engineering. Particles with tailored coatings are greatly desired for a range of different applications.Amorphous coatings applied via film coating or microencapsulation have frequently been described in thepharmaceutical context and usually result in homogeneous surfaces. In the present study we have been exploringthe feasibility of coating core particles with crystalline substances, a matter that has rarely been investigated. Theexpansion of the range of possible coating materials to include small organic molecules enables completely newproduct properties to be achieved. We present an approach based on temperature cycles performed in a tubularcrystallizer to result in engineered crystalline coatings on excipient core particles. By manipulating the processsettings and by the choice of coating substance we are able to tailor surface roughness, topography as well assurface chemistry.Benefits of our approach are demonstrated by using resulting particles as carriers in dry-powder-inhalerformulations. Depending on the resulting surface chemistry and surface roughness, coated carrier particlesshow varying fitness for delivering the model API salbutamol sulphate to the lung.