What is the best long-term storage condition for swabs that contain biological material?

The best long-term storage condition for swabs containing biological material is temperature-controlled storage if the swabs are dried. Storing dried swabs in a stable temperature environment prevents the growth of microorganisms and preserves the integrity of the biological material for future analysis. It minimizes potential degradation of DNA and other biological components that may occur if the samples are subjected to fluctuating temperatures or humidity.

Refrigeration, while helpful for short-term storage, can lead to moisture accumulation, which can compromise the sample and facilitate the growth of bacteria or mold. Freezing can also be beneficial in certain contexts, but it may lead to cell lysis or rupture of delicate biological structures, potentially rendering them unsuitable for certain types of analyses. Simply keeping the swabs dried is not enough unless combined with appropriate temperature control, as temperatures that are too high can trigger deterioration.

Overall, the combination of drying and temperature stability offers the best preservation method for biological evidence, ensuring it is suitable for testing even after prolonged storage.