Tribo-Charging Behaviour of Inhalable Mannitol Blends with Salbutamol Sulphate

Purpose The performance of carrier-based dry powder inhaler (DPI) formulations can be critically impacted by interfacial interactions driven by tribo-electrification. Therefore, the aim of the present work was to understand how distinct API particle characteristics affect the charging behaviour of blends intended for DPI delivery. Methods Salbutamol sulphate (SBS) particles engineered via spray-drying and jet milling were used as model APIs. D-mannitol was selected as a model carrier. The materials were characterized concerning their different particle properties and their charge was analysed alone and in blends before and after flow over a stainless-steel pipe. Results The spray-dried SBS (amorphous and spherical) charged positively and to a higher extent than jet milled SBS (crystalline and acicular) that charged negatively and to a lower extent. D-mannitol charged positively and to a higher extent than the APIs. All drug-excipient blends charged negatively and differences were found between the spray-dried and jet milled SBS blends at 2% and 5% drug loads. Conclusions It was demonstrated how distinct solid-states, particle shape, size and morphology as well as different water contents of the different materials can affect tribo-charging. For their binary blends, the amount and nature of fines seem to govern inter-particle contacts critically impacting charge evolution.