[DNA amplification on chemically structured chips in forensic STR analysis]

The present study deals with low-volume amplification of short tandem repeats (STRs) for forensic DNA analysis. A chemically structured chip in microscopic slide format was used to amplify standard forensic casework samples in a 1-microL reaction volume primarily with the well-known and widely used PowerPlex kit and with other commercially available STR kits. Tests regarding sensitivity, mixture analysis, robustness, reproducibility, buffer composition and technical performance were carried out to check the usefulness of this amplification strategy. The results obtained show that low-volume amplification is a promising option in the forensic DNA typing toolbox. Restrictions to this method, which are strictly related to the kit and the respective buffer used, were found in low copy number (LCN) DNA typing, mixture analysis and technical performance. Problematic typing results included artefact alleles, increase in locus and heterozygote imbalance, allelic and locus dropout as well as increase of stutters, especially when amplifying less than 200-300 pg of DNA. In contrast, convincing advantages are a higher sensitivity, better amplification efficiency and the low cost factor of this method.