Lyophilizers are invaluable tools in lab settings used to increase the shelf life of vaccines and other pharmaceutical products; freeze dryers can also facilitate the transportation of biopharmaceuticals. Additionally, some medicines can be freeze-dried in order to be easily absorbed, while some proteins and antibodies are freeze-dried for stability. Given the wild applications of lyophilization, it’s no surprise there’s a variety of lyophilizers experts can choose from. Whether it’s to set up a new laboratory or replace old equipment, there are three major factors to consider before purchasing a new unit:
Before buying a freeze dryer, experts should refine their research and production goals. Both the sample size and type are crucial factors to consider. While benchtop models are ideal for small volumes, floor standing models are beneficial for large scale applications. When it comes to sample types, a difference of 15-20°C is needed between the eutectic temperature of the sample and the collector chamber. While the majority of biological samples can be frozen by a standard system reaching -50°C, some samples, such as High-Performance Liquid Chromatography/HPLC preparations in acetonitrile/CH3CN, will need a cascade-type collector reaching -84°C to accommodate lower freezing points. An ultra-low temperature lyophilizer (of up to -105°C), on the other hand, might be required to accommodate preparations with methanol (with a eutectic point of -97.6°C). For acidic samples that can harm the stainless steel coils of a system, Polytetrafluoroethylene/PTFE coating is recommended, as well as a hybrid-type pump. Last but not least, the volume of liquid should be considered. While lyophilizers with a small capacity can accommodate tissue samples with small amounts of liquid, food products may hold higher amounts and require units with a bigger capacity. Note that collector capacities can vary from 2.5 to 18 liters, with different shelving and holders.
As explained above, different research goals require different equipment. Capacity parameters, materials used, and design types are all factors to consider. Yet, we should note that all lyophilizers follow three vital processes to execute water removal: 1) freezing to preserve the sample’s physical form; 2) sublimation drying that removes 95% of the water; 3) secondary drying or desorption drying used to remove any remaining water molecules. Interestingly, after lyophilization, products contain 1-4% moisture and are nitrogen sealed for further use. Note that lyophilization differs from evaporation (the use of heat to eliminate moisture), and sublimation refers to the direct transition from a solid to a gaseous state.
Lyophilization is an expensive process due to equipment costs, long processing times, and energy costs. Prices can vary according to the unit’s parameters (e.g., temperature range, capacity, type, and brand). Note that full-sized models can process multiple samples in a single cycle; some units may even have more than one condenser for almost continuous use. Control systems can also vary in complexity, with some allowing the programming of a whole freeze-drying recipe, which can also affect costs. Furthermore, drying accessories, which can be customized according to the research goals, should be considered. To test tubes and serum vials, for instance, flasks can be used, while for bulk samples, a tray dryer will be preferable. Additional equipment, such as glove boxes for toxic materials and accessories to stopper under vacuum, can increase the final price of a unit.