Effect of vacuum induced nucleation on the final product homogeneity

In the field of freeze drying of pharmaceutics the homogeneity of the sublimation flux during drying is fundamental to allow a final product with the same characteristics. Previous studies have shown that the control of freezing stage, in addition to a dramatic reduction of cycle duration, can also improve the homogeneity of the final batch. In this framework, this study is focused on the investigation of the effects of the Vacuum Induced Nucleation control method (modified in a previous work)[1,2] on the final structure of the product. Two aspects will be taken into consideration: the uniformity among vials of the same batch (inter-vial) and the uniformity of the structure along the height of the product (intra-vial). It has to be pointed out that a non-uniform product structure can have an impact on the protein aggregation and redistribution, and cause a partial cake collapse or micro-collapse. This investigation is really useful to define some limits of the control method used in this work.