1.3.5. Sample collection cards
Samples can also be dried on filter paper-based collection cards. In this case the molecules are stabilized primarily through desiccation, rather than low temperature, so thorough drying during sampling and low humidity during storage is essential for this method. The FTA™-cards produced by Whatman are furthermore impregnated with chemicals to prevent bacterial or enzymatic degradation of nucleic acids (Becker et al., 2004; Rensen et al., 2005). The method is ideal for liquid samples (blood, urine, sputum etc.) but has also been used for insect samples (Harvey, 2005) including honey bee larvae, pupae, extracted tissues and mites. Such filter-dried samples can be analysed for all manner of compounds (Jansson et al., 2003; Chamoles et al., 2004; Li et al., 2005; Zurfluh et al., 2005) including RNA (Karlson et al., 2003; Prado et al., 2005). The major advantages are the ease and reduced costs of collection, transport, labelling and long-term storage at room temperature, reducing the requirements for freezer space, boxes and tubes (Kiatpathomchai et al., 2004; Harvey, 2005; Karlson et al., 2003; Rensen et al., 2005; Prado et al., 2005). The major disadvantages are the uneven distribution of target across the filter paper and the gradual loss of target during prolonged storage (Chaisomchit et al., 2005). Samples collected on collection cards should therefore also be processed as soon as possible, by cutting out the entire dried sample and soaking this in an appropriate buffer, as recommended by the FTA™-card protocol, for the recovery of nucleic acids.
- FTA™ collection cards
- Samples: Tissues; faeces; eggs; larvae; pupae; mites.
- Use: Squash sample on card and air-dry.
- Storage: At room temperature in dry container. Not in freezer.
- Processing: Cut out sample and soak directly in extraction
buffer for 15 minutes. Proceed as for fresh samples.
- Pros: Excellent preservation; light; easy storage and indexing; versatile; preservation of faeces.
- Cons: Expensive; variable processing; uneven distribution across card; not suitable for adult bees, not suitable for bulk samples.