Comparison of different analytical methods in freeze-drying : DSC, Lyostat and Lyotherm

by biopharma-admin in BTL News, BTL Right Sidebar Content

August 2015

Lyostat vs. DSC

Lyostat4LED_analysis

 

This is a DSC to use (Medium)

 

DSC (Differential Scanning Calorimetry)  and  mDSC (modulated Differential Scanning Calorimetry) are thermal  techniques typically used  to identify the glass transition temperature (Tg) for the purpose of stability studies in dried samples. These techniques can also be used to analyse frozen samples for the development of a safely optimised freeze- drying cycle.

 

 

Lyostat4_LED

Lyostat is a Freeze-Drying Microscope (FDM), which allows the user to identify and record the ‘collapse’ temperature of a sample. It also provides  data on eutectic events and skin formation, showing the structure of the material as it dries  at  increasing temperatures in real time.

 

Collapse is the key temperature for freeze-drying.  Collapse is defined as the point at which the solute phase of the drying formulation cannot maintain its structural integrity upon removal of the solvent, resulting  in the formation of viscous flow. It occurs, more often than not, at a higher temperature than the glass transition (Tg).

 

Glass transition (Tg) is the reversible transition in amorphous materials from a hard and relatively brittle state into a molten or rubber-like state. Although glass transition is often considered as a pre-requisite in freeze-drying, the collapse temperature,  which  often occurs at significantly higher temperatures ,  is actually the most  key critical temperature.

 

 

 Analysis

Lyostat

DSC

Collapse Temperature

YES

NO

Designed for Freeze-Drying

YES

NO

Eutectic Events

YES

YES

Skin Formation

YES

NO

 

The Advantages of the Lyostat :

  • Lyostat is a valuable research and development tool, especially designed for freeze-drying
  • Lyostat analysis uses just 2µl and is typically complete in under an hour
  • Lyostat analysis is PC controlled to provide sophisticated image and data capture as well as analysis functions
  • Lyostat allows the user to make a video of their sample under analysis.
  • The software is also available in a 21CFR11 compliant version

 

Why should you need a freeze-drying microscope?

  • FDM analysis allows you to define the exact «collapse» temperature of your sample, which cannot be done with a DSC. The knowledge of a product’s collapse behaviour is  vital, as a product that collapses during freeze-drying can suffer from a range of problems including reduced shelf life, reduced activity and poor reconstitution.
  • Using the onset of collapse as the basis of a cycle will allow a higher temperature than using the glass transition temperature, which will mean faster drying.
  • FDM allows you to observe the drying sample behaviour and to obtain data which will enable you to develop new formulations and new cycles using a systematic approach rather than trial and error.
  • FDM will also enable you to scale up or optimise existing processes.

 

Lyotherm vs. DSC

lyotherm

Lyotherm is a powerful tool for characterising frozen formulations. It provides more information than frozen state DSC analysis, because it performs simultaneous impedance and thermal analysis.

 

 Analysis

Lyotherm

DSC

Glass Transition Temperature (Tg)

YES

YES

Crystallisation Events

YES

YES

Eutectic Events

YES

YES

Softening of Material With or Without Thermal Changes

YES

NO

Designed for Frozen Materials and Freeze Drying

YES

NO

 

The Advantages of the Lyotherm:

  • Lyotherm allows combined electrical impedance and differential thermal analysis (DTA) of frozen samples
  • Impedance analysis reveals information about the rigidity (molecular mobility) of frozen
  • DTA is a similar technique to DSC, providing thermal data at the same time as impedence analysis
  • Changes in rigidity are not always associated with thermal changes so you don’t always see them in DSC or DTA analysis.

 

Why should you need a Lyotherm?

  • Impedance shows softening of samples even when no thermal change occurs, which can be particularly relevant to biological products : storage of frozen material in softened state can reduce shelf life
  • Freeze drying sensitive products in a softened state but below the onset of collapse temperature can cause problems with reduced activity and poor reconstitution
  • Lyotherm analysis lets you observe the glass transition temperature and any crystallisations or eutectic melt events , which allows you to create a cycle with appropriate freezing, annealing and drying conditions
  • As the majority of products for freeze drying are amorphous to varying degrees, Lyotherm is indispensable to analyse products undergoing freeze drying.

 

Comparison of Analytical Techniques

The graphs below show the frozen state analysis of amorphous material* with mDSC and Lyotherm. With the mDSC analysis no significant changes were detected. However softening and glass transition were detected with the Lyotherm. While DSC is ideal to test dry samples,  Lyotherm, which has been especially designed for freeze-drying, will provide additional data for frozen samples.

* An experiment was performed in Biopharma House, Winchester in 2015. A series of typical amorphous formulations were analysed using a range of techniques.The following graphs show the results for MDSC and Lyotherm for one of the formulations.

 

Sample Analysis by mDSC

Formulation 2 DSC CLEAN_v2

* No specific change in the product between –70°C and 0°

* No indication of glass transition

 

 

Sample Analysis by Lyotherm

Formulation 2 Lyotherm CLEAN_with lines_v2

* Impedance analysis shows glass transition at –50°C

* Softening of the frozen material shown at –37°C preceding collapse

 

As the majority of products for freeze drying are amorphous to varying degrees, Lyotherm is indispensable to analyse products undergoing a freeze drying stage.

 

BTL’s Services

Over the past 15 years BTL has worked with over 1000 products and uses state of the art analytical equipment to characterise material before and after freeze drying. Biopharma Technology Ltd assists customers with all challenging aspects of freeze-drying as part of our Consultancy and R&D division, for example:

  1. Product Characterisation
  2. Formulation Development
  3. Cycle Development
  4. Production
  5. Troubleshooting
  6. Sell the analytical instruments Lyostat 4 and Lyotherm 2, for formulation characterization
  7. We offer training courses in freeze-drying