title: Automated Forensic Animal Family Identification by Nested PCR and Melt Curve Analysis on an Off-the-Shelf Thermocycler Augmented with a Centrifugal Microfluidic Disk Segment.
abstract: Nested PCR remains a labor-intensive and error-prone biomolecular analysis. Laboratory workflow automation by precise control of minute liquid volumes in centrifugal microfluidic Lab-on-a-Chip systems holds great potential for such applications. However, the majority of these systems require costly custom-made processing devices. Our idea is to augment a standard laboratory device, here a centrifugal real-time PCR thermocycler, with inbuilt liquid handling capabilities for automation. We have developed a microfluidic disk segment enabling an automated nested real-time PCR assay for identification of common European animal groups adapted to forensic standards. For the first time we utilize a novel combination of fluidic elements, including pre-storage of reagents, to automate the assay at constant rotational frequency of an off-the-shelf thermocycler. It provides a universal duplex pre-amplification of short fragments of the mitochondrial 12S rRNA and cytochrome b genes, animal-group-specific main-amplifications, and melting curve analysis for differentiation. The system was characterized with respect to assay sensitivity, specificity, risk of cross-contamination, and detection of minor components in mixtures. 92.2% of the performed tests were recognized as fluidically failure-free sample handling and used for evaluation. Altogether, augmentation of the standard real-time thermocycler with a self-contained centrifugal microfluidic disk segment resulted in an accelerated and automated analysis reducing hands-on time, and circumventing the risk of contamination associated with regular nested PCR protocols.
authors.affiliation: Laboratory for MEMS Applications, IMTEK-Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany; Hahn-Schickard, Freiburg, Germany.
authors.forename: Mark
authors.initials: M
authors.lastname: Keller
authors.affiliation: Institute of Legal Medicine, Freiburg University Medical Center, Freiburg, Germany; Faculty of Biology, University of Freiburg, Freiburg, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Naue
authors.affiliation: Laboratory for MEMS Applications, IMTEK-Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany; Hahn-Schickard, Freiburg, Germany; BIOSS-Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Zengerle
authors.affiliation: Laboratory for MEMS Applications, IMTEK-Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany; Hahn-Schickard, Freiburg, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: von Stetten
authors.affiliation: Institute of Legal Medicine, Freiburg University Medical Center, Freiburg, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Schmidt
mesh_terms: D000818:Animals; D001331:Automation; D002498:Centrifugation; D044707:Forensic Sciences; D044085:Microfluidics / Q000295:instrumentation*; D016133:Polymerase Chain Reaction / Q000379:methods*