A procedure of silver staining for nucleic acids in agarose gels without pretreatment or drying steps

In this paper, we report a fast, simple, and reproducible staining protocol for nucleic acids in agarose gels with a sensitivity in the order of 10 pg/mm2. It took only three steps: fixation, incubation with silver ions, and development of the gels (total time 50 min). The resulting calibration curves (area vs ng of loaded DNA) after a densitometric scanning of agarose gels stained with this procedure were linear up to 50 ng of double-stranded DNA. We found this method suitable for routine laboratory use and especially appropriate for densitometric analysis due to homogeneous background development. Furthermore, it avoids the pretreatment and/or drying steps proposed by other authors for agarose gels.