Abstract:
Lyophilisation is used to preserve protein drugs in the solid amorphous form. To further improve the protein drug stability, stabilisers such as disaccharides are added to the formulations. Being in an amorphous state, the lyophilised protein-stabiliser system tends to exhibit phase separation upon storage. The aim of this study is develop quantitative method to characterise the phase behaviour of lyophilised protein-disaccharide systems. Bovine serum albumin (BSA) and sucrose or trehalose were used as model protein and disaccharide, respectively. The protein-disaccharide mixtures were prepared at various weight ratios, lyophilised and stored up to 45 days at 45 C (below the formulations’ Tg) and 65 C (close to formulations’ Tg). The lyophilised mixtures were characterised by Fourier transformed infrared (FTIR) spectroscopy and imaging, differential scanning calorimetry (DSC) and size exclusion chromatography (SEC). DSC analysis showed that all BSA-disaccharides systems showed a single Tg, suggesting a one-phase miscible system. Chemical maps from FTIR imaging of BSA (1480-1600 cm-1) and disaccharides (900-1010 cm-1) demonstrated that it can be used as an alternative and analytical tool to detect miscibility of binary amorphous formulations. The explorative molecular distribution characterisation opens up a new possibility in complementing other solid state analytical techniques such as DSC, SEM and HPLC-SEC to detect phase behaviour in binary amorphous systems
Keywords: Lyophilisation, binary system, BSA, trehalose, sucrose, polyvinylpyrollidone, polyvinyl alcohol, dextran, glass transition temperature, spectroscopic imaging/mapping, differential scanning calorimetry, high performance liquid chromatography, scanning electron microscopy.
