Analysis of protein physical stability in lipid based delivery systems--the challenges of lipid drug delivery systems

Lipid based systems are a promising delivery system for many drug molecules, including labile compounds such as peptides and proteins. However, in the development of these systems the effect on the physical stability is rarely taken into account. Physical changes are often correlated with changes in biological activity but are generally much easier to assess. The present paper illustrates the use of a combination of techniques, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and intrinsic tryptophan fluorescence, to determine structural changes of proteins in lipid based systems such as solid lipid nanoparticles and emulsions.