Proper Handling and Storage of Samples for Assay
The accurate and reliable results of any assay are heavily dependent on the proper handling and storage of the samples being tested. My focus in this article is to look at some of the critical factors that influence sample integrity and the methods employed to ensure optimal preservation.
Freezing for Preservation
Freezing is a widely used method for preserving samples due to its ability to significantly slow or halt biochemical and cellular processes. By lowering the temperature, the degradation of enzymes, nucleic acids, and other sensitive components is minimized. However, the effectiveness of freezing as a preservation technique depends on several factors.
The appropriate duration for freezing samples varies significantly based on the specific sample type and its composition. Some samples may be suitable for short-term freezing, while others require long-term storage at ultra-low temperatures. For instance, samples containing volatile compounds or those that are highly susceptible to degradation may need to be stored at temperatures well below -80°C.
Note that repeated freeze-thaw cycles can have a detrimental effect on sample integrity. When a sample is frozen and then thawed, the ice crystals that form can disrupt cellular structures and damage biomolecules. Therefore, it is essential to handle samples carefully and store them in a stable environment to minimize the number of freeze-thaw cycles. This may involve using appropriate cryoprotectants or ensuring that samples are frozen and thawed in a controlled manner.
Shipping Requirements
When samples need to be transported to a remote laboratory for analysis, special precautions must be taken to ensure their integrity during transit. This is particularly important for samples that are sensitive to temperature fluctuations or those that are susceptible to degradation at higher temperatures. This can be achieved by using appropriate packaging materials and shipping methods. For instance, samples can be placed in insulated containers and surrounded by dry ice or a gel pack to maintain a cold environment.
Speaking of dry ice, this is a common method for shipping frozen samples. It is a solid form of carbon dioxide that sublimates at a very low temperature, providing a cold environment to keep samples frozen. However, it is important to note that dry ice has a limited lifespan, and careful planning is necessary to ensure that samples arrive at their destination before the dry ice sublimates completely. This may involve using a sufficient amount of dry ice, selecting an appropriate container, and considering the duration of the shipping process.
Considerations for Enzyme Preservation
Enzymes are biological catalysts that play a vital role in numerous cellular processes. Due to their delicate nature, enzymes are particularly susceptible to denaturation or destruction when exposed to unfavorable conditions, such as temperature fluctuations. Refreezing samples can be detrimental to certain enzymes, like transaminases. This is because repeated freezing and thawing cycles can disrupt the enzyme’s structure and impair its function. The formation of ice crystals during freezing can cause physical damage to the enzyme molecules, leading to loss of activity. Therefore, it is essential to minimize the number of freeze-thaw cycles by handling samples carefully and storing them in a stable environment. Use appropriate storage conditions and transportation methods to help ensure the integrity of enzyme samples and maintain their catalytic activity.
Closing Thoughts
The proper handling and storage of samples are essential for ensuring the accuracy and reliability of assay results. Freezing is a common method for preserving samples, but the duration of storage and the need to avoid freeze-thaw cycles should be carefully considered. For samples that need to be transported, maintaining low temperatures and using appropriate packaging materials is crucial. And lastly, enzymes are particularly sensitive to temperature fluctuations and can be easily denatured. Avoiding unnecessary freezing and thawing cycles and maintaining a stable temperature is essential for preserving enzyme activity.
Matthew A. Webster, MA, MS, ED.D, LPC
Martin Counseling, PLLC in Katy, TX.
Dr. Matt Webster is a professional educator, nutritionist, and therapist located in the Houston, Texas area. He specializes in couples therapy, sexuality, and maladaptive eating patterns with a focus on the role of nutrition. More About Matt >>
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