Reagents and assays that are to be freeze-dried possess a critical temperature known as the collapse temperature, often denoted Tc, which it is essential not to cross during freeze-drying. It is important to maintain the temperature below Tc until drying is completed. If the product is maintained too far below this temperature it can lead to an unacceptably slow drying process.
The collapse temperature for commonly used cryo-preservatives in molecular assays is often found to be around 4oC higher that the products glass transition (Tg) point. Therefore, it is valuable to know this critical temperature for a formulation prior to lyophilisation, in order to create a suitable lyophilisation program. If required a suitable cryo-preservative solution can be developed to modify reagents for freeze-drying.