Shipping biological materials such as RNA, cells, and tissue samples over long distances presents a number of challenges, particularly when maintaining their integrity, functionality, and biological activity is crucial. Whether for research, diagnostics, or clinical purposes, improper handling and transport conditions can lead to sample degradation, contamination, or loss of viability.
Therefore, developing a well-planned shipping strategy is essential to ensure that these delicate materials reach their destination in optimal condition. In this article, we will explore the key strategies and best practices for protecting RNA, cells, and tissue during long-distance shipping.
1. Protecting RNA: Handling and Shipping Strategies
RNA is highly susceptible to degradation due to the ubiquitous presence of RNases (enzymes that break down RNA) and environmental factors such as heat, moisture, and pH fluctuations. Preserving the integrity of RNA during transport requires meticulous handling and a few specific steps:
a. RNase-Free Environment
Before even considering shipping, it's crucial to minimize the risk of RNase contamination. This includes using RNase-free consumables, gloves, and reagents during RNA isolation and sample preparation. Maintaining an RNase-free environment helps ensure that RNA samples remain intact during shipping.
b. Proper Sample Preparation
Stabilizing RNA before shipment is critical to avoid degradation. There are several methods for preparing RNA samples, including:
Stabilizing Reagents: Reagents like RNAlater® or DNA/RNA Shield stabilize RNA at ambient temperatures. This solution can be used to protect RNA from degradation for short to medium-term storage without the need for freezing, which is particularly useful during shipping. It makes the shipping cost lower than with dry ice, but need to remove the protect reagent before proceeding next experiments.
Lyophilization (Freeze-Drying): For long-distance shipping, lyophilization is an effective method. The freeze-drying process removes moisture from RNA, leaving it in a stable powder form. Once rehydrated at the destination, the RNA can be used without significant loss of quality.
Freezing: Storing RNA at -80°C and shipping on dry ice is another option for preserving RNA. This is commonly used for high-quality RNA that is particularly sensitive to degradation, but increased shipping cost.
2. Protecting Cells: Viability and Functionality During Transport
Maintaining the viability and functionality of live cells during long-distance transport is particularly challenging. Cells are delicate and can easily lose their viability if exposed to extreme temperatures, physical shock, or unfavorable environments during transit.
a. Cryopreservation
One of the most effective methods for preserving cells for long-distance shipping is cryopreservation. This involves freezing cells at very low temperatures (typically in liquid nitrogen or on dry ice) in the presence of cryoprotectants such as 10% dimethyl sulfoxide (DMSO). The key steps for protecting cells during cryopreservation include:
Optimized Freezing Protocol: Cells should be frozen gradually to avoid the formation of ice crystals, which can damage cell membranes. Typically, a controlled-rate freezing device is used to lower the temperature gradually to -80°C before transferring the cells to liquid nitrogen storage (-196°C).
Use of Cryoprotectants: Cryoprotectants like DMSO help to prevent ice formation inside cells during the freezing process. Ensuring the correct concentration of cryoprotectant is critical for preserving cell viability.
b. Shipping on Dry Ice
For short-term transport, dry ice can maintain frozen cells at a sufficiently low temperature to preserve their viability. Specialized shipping containers with enough dry ice must be used to ensure that the temperature remains stable throughout the journey. Shipping on dry ice also reduces the risk of temperature fluctuations that could compromise cell health.
c. Fixation 10X Genomics recommends methanol fix method to protect RNA in cell and can minimize the mRNA expression pattern changes.
The demonstrated protocol (CG0000776) can be found in www.10xGenomics.com.
d. Alternative Methods for Short-Term Transport
If cryopreservation is not feasible, cells may be transported in specially formulated media designed to keep them viable at room or low temperatures for short periods. This method, while more prone to variability, can be useful for shipping cells that are expected to be revived or used quickly upon arrival.
3. Protecting Tissue Samples: Ensuring Integrity and Viability
Shipping tissue samples poses a distinct set of challenges, especially when the preservation of tissue architecture, cell viability, or molecular integrity is critical for downstream applications such as histological analysis, genomic studies, or transplantation. Tissue can degrade quickly if exposed to unfavorable environmental conditions, so careful planning is essential.
a. Freezing
For tissues intended for molecular analysis (such as RNA or DNA extraction), freezing is the most reliable method for long-distance shipping. Tissue samples can be flash-frozen using liquid nitrogen or stored at -80°C and transported on dry ice. This method is particularly effective at preserving the molecular components of the tissue but may compromise histological structure.
b. Fixation
For histology or immunohistochemistry applications, fixation is a widely used method. Formalin fixation is one of the most common techniques, preserving tissue morphology for analysis at the destination. Once fixed, tissue samples can be transported at ambient temperature, reducing the complexity of shipping logistics.
RNAlater® or DNA/RNA Shield® for Tissue: In situations where preserving both tissue structure and molecular integrity (e.g., RNA and DNA) is important, RNAlater® or DNA/RNA Shield® can be used to stabilize tissue samples. These reagents preserves nucleic acids and proteins at ambient temperatures, making it a convenient choice for shipping tissues without the need for freezing.
c. Cryopreservation of Tissue
For applications requiring viable tissue, cryopreservation is the gold standard. The tissue is typically immersed in a cryoprotectant solution and slowly frozen before long-term storage in liquid nitrogen. Shipping cryopreserved tissue samples on dry ice ensures that tissue viability is maintained during transport.
4. Packaging and Regulatory Considerations
In addition to sample preparation and choosing the appropriate shipping conditions, it's important to use proper packaging materials and follow regulatory guidelines for shipping biological materials. Here are some critical considerations:
Insulated Shipping Containers: Insulated containers maintain the required temperature and protect samples from environmental fluctuations. These containers are essential for shipments requiring dry ice or liquid nitrogen.
Regulatory Compliance: Depending on the type of biological material being shipped, regulatory requirements may apply. Ensure that the shipment complies with International Air Transport Association (IATA) regulations and that appropriate permits or labels are in place, especially for cross-border shipments.
Documentation: Always include proper documentation, including material transfer agreements (MTA), customs declarations, and handling instructions to ensure that the recipient and shipping personnel can properly manage the materials.
Conclusion
Protecting RNA, cells, and tissue samples during long-distance shipping requires careful planning, appropriate preparation methods, and controlled shipping conditions. Whether preserving RNA integrity, maintaining cell viability, or keeping tissue samples intact for histological or molecular analysis, the key to successful transport lies in understanding the unique needs of each biological material. By selecting the right preservation methods and using appropriate packaging, researchers and clinicians can ensure that their valuable samples arrive at their destination in optimal condition, ready for immediate use or further study.