Lyophilizers, or freeze dryers, are used to increase the long term stability of nanomaterials and make nanomaterial development easier. When selecting a lyophilizer for nanoparticles it is important to remember that nanoparticles can be difficult to freeze dry and may require extreme conditions in a lyophilizer.
Freeze drying requires three steps: pre-freezing, primary drying and secondary drying. When formulating nanoparticles, you must determine the correct types of bulking agents, stabilizers and lyoprotectents that work with your specific nanoparticles of interest. Certain processes of freeze drying, such as pre-freezing and sublimation can destabilize nanoparticles, so the above factors are important to consider prior to lyophilization.
Pre-freezing involves freezing the sample prior to pulling a vacuum to prevent loss of sample and ensure proper lyophilization. Once the samples are frozen, primary drying begins by adding controlled heat to the samples through the shelves and pulling a deep vacuum with exposure to a very cold condenser. Frozen water molecules will sublimate or leave the sample and collect in the coldest spot in the closed system. For best results, we recommend setting the shelf temperature 3° to 5°C below the sample’s collapse temperature for primary drying. During primary drying, 92 - 93% of the moisture is removed. A crust forms at the sample surface and heat is required to drive out the residual moisture remaining in the sample.
Secondary drying begins when the only water molecules remaining are the unfrozen ones that are bound to the sample. To release these bound water molecules, heat is required to break the bonds. After the moisture in the sample is reduced by another 5%-6% secondary drying is complete and the samples can be stoppered under vacuum or nitrogen for long term storage if desired. The small size of the nanoparticles makes it is hard to predict their properties under varying conditions. Because nanoparticles can be very challenging to freeze dry, they require a sophisticated freeze dryer that can provide a wide temperature range in the sample shelves and condenser.
The Labconco Triad Freeze Dry System has a 2.5L collector condenser that reaches -85°C, which can handle some solvents such as chloroform. The shelves can pre-freeze to -75°C and during primary drying can go as low as -55°C. These deep temperatures are not reached on standard freeze dryers and are often utilized when a sample is difficult to freeze dry or has solvents in the sample.
Once a freeze drying protocol has been developed, the Triad’s microprocessor controlled temperature programming with 5 user set programs and 6 segments per program make freeze drying a simple, one button operation. After the freeze dry run is complete, the Triad can be backfilled with nitrogen or simply remain under vacuum as the samples are stoppered with the single, stoppering shelf ensuring long term sample stability. The Triad can accommodate up to 196 x 10ml samples per run.
Nanomaterials offer so many promising breakthroughs in science and prove to researchers that face the challenges of handling them, that smaller is not always easier. However, the Labconco Triad has the features and versatility to make freeze drying the most challenging samples easy.
Jenny Sprung, Product Manager, Labconco Corporation
88114 Prospect Avenue
Kansas City, MO 64132
Toll free: 800-732-0031