MEASUREMENT OF Tg IN LYOPHILIZED PROTEIN AND PROTEIN EXCIPIENT MIXTURES BY DYNAMIC MECHANICAL ANALYSIS

The glass transition of lyophilized materials is normally measured by conventional or temperature modulated differential scanning calorimetry (TMDSC). However, because of the weakness of these transitions when protein concentrations are high, these techniques are often unable to detect the glass transition (T-g). High ramp rate DSC, where heating rates of 100 K per min and higher are used, has been shown to be able to detect weak transitions in a wide range of materials and has been applied to these materials in previous work. Dynamic mechanical analysis (DMA) is also known to be much more sensitive to the presence of relaxations in materials than other commonly used thermal techniques. The development of a method to handle powders in the DMA makes it now possible to apply this technique to protein and protein-excipient mixtures. HRR DSC, TMA and DMA were used to characterize the glass transition of lyophilized materials and the results correlated. DMA is shown to be a viable alternative to HRR DSC and TMA for lyophilized materials.