This has been a major interest for a number of years. We take a close look at the spray drying of proteins mainly for parenteral application. Spray drying is actually of gentle way of handling a sensitive biological, and in many ways no less attritious than freeze drying. We have examined the morphology of spray dried sugar/protein systems, and looked at protein damage during the process and also on subsequent storage. What actually happens to the conformation and activity of protein molecules during nebulization and subsequent drying of liquid droplets ? We have developed a new kinetic technique to examine continuously the changes taking place in a protein during droplet drying. You can read more about this device here: 1,2,3,4.
The properties of mixed amorphous/crystalline adjuvents for peptides are still not clear. These can be used to give improved cake appearance compared to shrunken pure amorphous systems, but have disadvantageous Tg’. We investigate the complex relations between formulation, Tg` and primary drying rate using the freeze-drying balance. The causes and measurement of shrinkage of amorphous cakes is also under close examination. This apparently simple phenomenon is surprisingly complex. We are starting to develop a technique for determining the kinetics of shrinkage and cracking.
There are a number of problems in the development of new TTSs based on pressure sensitive adhesives. We tackle these in a systematic manner by concentrating on the relatioin between thermodynamic activity (really just the degree of saturation) and release or permeation. The first problem to be tackled is simply how to define and measure the solubility of a low molecular weight drug in a polymeric thin film. Once we have a selection of polymers in which a drug has different solubility we can deduce the importance of thermodynamic activity for diffusional processes. This is quite tricky, but also has very practical applications for future TTS development. Further issues are the influence of additives on drug solubility in a thin polymer film.