Freeze Drying Microscopy - Freeze Drying Microscopes

Freeze Drying Microscopy
Richard Taylor & Suling Zhai
Department of Chemical Engineering
University of Cambridge, Cambridge CB2 3RA, UK
Extract from "Pharmaceutical Drying Technology"
Dry pharmaceutical formulations are required for a number of exciting emerging drug delivery technologies. These new devices which enable the needle free entry of drugs to the blood stream via inhalable and transdermal routes require drugs prepared as high performance particulate dry powders.
The distribution of drugs in a freeze dried form, in vials, is very well established pharmaceutical practice. Our work is focused on understanding the biochemical and physical mechanisms underlying the drying process and the effect of drying on biological entities. Despite the importance of drying technology to current, and future pharmaceutical practice, the mechanisms underlying both the drying process and stability of biological entities have not been fully characterised. We apply the knowledge we gain to the design of novel processes and formulations.
Freeze dried vaccines that could be transported around the world without the need for refrigeration were crucial to the eradication of smallpox, confining images such as the one shown here to history. Building on their successful past, dried formulations have a promising future in an expanding variety of pharmaceutical applications.
Freeze Drying Microscopy
Using this technique we can observe the progress of a drying front. Watching this process is just like watching paint dry ...

This area of our research focuses on the mass transfer processes that occur during lyophilisation primary drying. Using freeze-drying microscopy (FDM) the effective diffusion coefficient [Define] for the transport of water vapour through the dried cake was determined.
The freeze-drying microscope consists of a small freeze-drying chamber (Microstat, Oxford Instruments, UK) containing a temperature-controlled copper stage and an optical window through which the progress of drying in sample can be observed via a microscope.

Complete article is available online.