Biologicals cover a wide range of materials which are often labile in solution and require lyophilization to stabilize I them. For instance Factor VIII activity begins to fall as soon as a sample of plasma is taken and whether a purified concentrate from plasma or a recombinant product of DNA technology is considered, both show loss of activity during processing and on storage and so one of the challenges of formulation is to stabilize the biological material for the shelf life of the product [1]. In order to do this water is removed by lyophilization and this usually reduces the degradation rate significantly. Towns [2] reviewed the interaction between water and proteins; stripping the water to below a monolayer covering of the surface of the protein generally engenders greater dry-state stability. Higher water content in lyophilized material plasticises the protein and allows for greater mobility as well as lowering the glass transition temperature, which can impact stability however formulation must be optimized so as to protect the dehydrated biological from damage [3].
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