The extraction of DNA on the system used guanidinium thiocyanate (Teknova, Hollister, CA) chemical lysis and solid phase DNA separation and purification with paramagnetic beads (Micromod GmbH, Germany) [19]. Two DNA extraction parameters were evaluated to verify the optimized performance of extraction. Boundary studies on two instruments were performed around the standard set of conditions for concentration of paramagnetic beads in 500 μL of lysis buffer and the incubation time for DNA binding to the beads. Bead concentrations tested were: 0.5×, 1×, 1.5×, and 2× and bead incubation times were: 1.5 min, 3 min and 6 min. The standard conditions are

indicated in bold. Six swabs of 1000 M with 100,000 cell load were used for each condition tested. The robustness of the extraction method to remove PCR inhibitors was challenged using model systems BIBW2992 datasheet to simulate what may be encountered from buccal swab collection. Three models of PCR inhibition—coffee, tobacco, and hematin—were Vorinostat order used, and dilutions of each inhibitor were added to 1000 M control swabs containing 25,000 or 100,000 cells. Three replicates for each cell load and inhibitor dilution were performed. The inhibitors were prepared as follows: (1) Brewed black coffee was purchased from Starbucks® and 2 μL, 10 μL, 50 μL, and 100 μL aliquots were pipetted directly onto 1000 M swabs; (2) 2.5 g of Grizzly long cut chewing tobacco (American Snuff Company) was mixed with

25 mL of water, ground in a pestle and mortar, and soaked over the course of a four-hour period. The tobacco slurry was

stored overnight at room temperature and the next morning 2 μL, 10 μL, 50 μL, and 100 μL aliquots of the supernatant were pipetted onto 1000 M control swabs; (3) hematin stock solution of 2 mM was made by dissolving hematin (Sigma–Aldrich, St. Louis, MO) in 0.1 N NaOH and then diluted in sterile water to desired concentrations. Farnesyltransferase 20 μL of each dilution (0.3 mM, 0.6 mM, 1.0 mM, and 2.0 mM) were pipetted onto 1000 M control swabs. The experiments with swabs were performed using three instruments. A mock hematin inhibition study was also performed using the traditional bench methods (e.g. 9700 and 3130xL). PCR reactions were prepared in duplicate with 2 ng of control DNA 007 containing hematin concentrations of: 0 mM, 0.25 mM, 0.3 mM, 0.35 mM, 0.4 mM, 0.45 mM, 0.5 mM and 1 mM and amplified for 28 cycles. The PCR products were separated and analyzed as previously described. The robustness of the GlobalFiler Express assay was tested with an EDTA inhibition study. 0.5 M EDTA (Ambion, TX) was diluted in sterile water and then added directly into the STR reaction vial to final concentrations of 0.1 mM, 0.25 mM, 0.5 mM, 1.0 mM and 1.5 mM. 1000 M control swabs with 25,000 or 100,000 cells were used to test the effect of EDTA addition on generation of a DNA profile. Three replicates for each cell load and inhibitor concentration were performed.