Removal of PCR Inhibitors using Silica-Based Spin Columns: Application to Ancient Bones

We describe a rapid and effective method for removing PCR inhibitors from DNA samples isolated from old or ancient bones. DNA was isolated from five bone samples ranging in age from 15 to 5000 years. Bone powders were subjected to prolonged digestion with proteinase K, followed by phenol-chloroform extractions. The DNA extracts were then concentrated using Centricon™ 30 microconcentrator units. Of the five samples tested using PCR, one showed only weak amplification and one had no detectable amplification product. The DNA samples were subsequently run through silica-based spin columns (QIAquick™ columns). This treatment was effective in removing all traces of pigment from the final DNA preparations and, more importantly, resulted in enhanced PCR amplification. This simple protocol may have general applications to forensic cases in which PCR inhibitors prevent the amplification of samples containing adequate amounts of DNA for PCR typing.