Direct amplification of STRs from blood or buccal cell samples

Abstract

Forensic databasing laboratories routinely analyze blood or buccal cell samples deposited on FTA ® paper. Prior to PCR amplification of the STRs, the FTA ® samples must undergo multi-step sample purification protocols to remove the PCR inhibitors present within the sample and from the FTA ® paper. The multi-step sample purification protocols are laborious, time-consuming and increase the potential for sample cross-contamination. To eliminate the need for DNA purification, we conducted studies to optimize the PCR buffer and thermal cycling parameters to allow for direct amplification of STRs from blood or buccal samples on FTA ® paper. We evaluated the effect of various factors on the DNA profile including: FTA ® disc size, blood sample load variation, and buffer formulation. The new STR assay enables the direct amplification of DNA from single source samples on FTA ® discs without sample purification. The new STR assay improves the workflow by eliminating tedious steps and minimizing sample handling. Furthermore, the new STR assay reduces cost by eliminating the need for purification reagents and expensive robots.