FTA cards (short for “Fixative, Transport, and Analysis cards”) are specialized cellulose-based matrices designed for the long-term preservation of blood samples and subsequent DNA analysis. Developed to address the challenges of traditional liquid blood storage—such as refrigeration requirements, microbial growth, and sample degradation—FTA cards integrate chemical reagents (e.g., chaotropic salts, chelating agents, and antimicrobial compounds) that immediately fix blood cells, inactivate nucleases, and prevent microbial contamination. This technology has revolutionized field-based blood collection, enabling samples to be stored and transported at room temperature for years while maintaining high-quality DNA suitable for PCR, genotyping, and sequencing. From clinical diagnostics to forensic investigations and epidemiological surveys, FTA cards have become a staple tool for reliable, cost-effective blood DNA preservation.
Working Principle & Operation Steps
FTA cards rely on a multi-step chemical process to preserve blood samples and stabilize DNA, with a straightforward workflow suitable for field or lab use:
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Sample Application: A small volume of whole blood (50–100μL, approximately 1–2 drops) is spotted directly onto the labeled circles of the FTA card. For dried blood spots (DBS), the card is held horizontally to ensure uniform spreading without pooling.
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Fixation & Preservation: The card’s reagents immediately lyse blood cells, release DNA, and denature proteins (including nucleases that degrade DNA). Chaotropic salts disrupt cell membranes, while chelating agents (e.g., EDTA) bind metal ions required for nuclease activity, and antimicrobials prevent bacterial/fungal growth.
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Drying: The card is air-dried at room temperature for 1–2 hours (or 30 minutes in a fume hood). Drying is critical—moisture残留 can lead to sample degradation or cross-contamination. The card is then stored in a sealed plastic bag with a desiccant to absorb ambient moisture.
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DNA Extraction for Analysis: A small punch (2–3mm diameter) is taken from the blood-spotted area using a sterile punch tool. The punch is washed 2–3 times with FTA purification buffer (or TE buffer) to remove reagents and residual hemoglobin, then dried. The purified punch is directly added to PCR reactions, as the DNA remains bound to the card matrix and is released during PCR thermal cycling.
Key Features
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Room-Temperature Stability: Preserves DNA for up to 10+ years at 15–25°C, eliminating the need for refrigeration or freezers during storage/transport.
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Microbial & Nuclease Inactivation: Integrated reagents prevent microbial growth and nuclease activity, ensuring DNA integrity even in warm or humid conditions.
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Minimal Sample Volume: Requires only small blood volumes, making it ideal for pediatric samples, wildlife studies, or resource-limited settings.
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Cost-Effective & Portable: Lightweight, compact, and cheaper than liquid storage tubes, reducing shipping costs and logistical burdens for fieldwork.
Scope & Applications
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Clinical Diagnostics: Storage of patient blood samples for genetic disease testing (e.g., sickle cell anemia), infectious disease surveillance (e.g., HIV, malaria), and pharmacogenomics.
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Forensic Science: Preservation of blood evidence from crime scenes (e.g., dried blood stains) for DNA profiling, with long-term stability supporting cold case investigations.
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Epidemiological Research: Large-scale blood collection in remote or resource-poor regions to study disease prevalence, genetic diversity, or population health trends.
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Wildlife Conservation: Collection of small blood samples from endangered species for genetic monitoring, parentage analysis, or disease screening without requiring immediate lab access.