Noncryogenic preservation of mammalian tissues for DNA extraction: an assessment of storage methods.

Reliable field methods for the storage of tissues to be used for DNA extraction and amplification are critical to many studies employing molecular techniques. Protection from DNA degradation was compared among three commonly used methods of noncryogenic storage of tissues over a time scale of 2 years. All three methods prevented DNA degradation during storage for at least 6 months. DMSO (dimethyl sulfoxide)-salt solution provided the best protection from DNA degradation of tissues stored for up to 2 years. High molecular weight DNA was recovered from lysis buffer in which tissue was stored for 2 years, however, moderate amounts of degraded DNA was also present. High molecular weight DNA was recovered from tissues stored in ethanol for 2 years, however the yield was relatively small compared to the other two noncryogenic storage techniques. Much of the DNA degradation in ethanol preserved tissues appeared to occur during the extraction procedure and can be reduced by soaking the tissue in lysis buffer for a few hours prior to beginning the extraction. The yield of PCR products was greatest from DNA extracted from DMSO-salt solution preserved tissues, whereas DNA from tissues stored in either lysis buffer or ethanol produced lower yields.