ABSTRACT
Objective To study the effect of silica in soil on the extraction of biological evidence DNA at the crime scene using the silica bead method.Methods Mud suspension and diluted blood were mixed to prepare biological samples mixed with dust and soil,which is to simulate biological evidence at the crime scene.Cell lysis was performed using heating lysis and guanidine salt chemical lysis,respectively.DNA was extracted using the silica bead method,amplified by PCR using Identifiler Plus kit and detected by capillary electrophoresis.The electrophoresis results were compared.Using mud suspension instead of silica beads to extract diluted blood DNA to validate the effect of silica in soil on the extraction of biological evidence DNA at crime scene using silica beads method.Results The complete STR loci were obtained after the extraction and amplification of 4 μL,20 μL dilute blood mixed with mud and lysed with heating cracking,whoes average peak heights arel 969.7±376.9 RFU and 9 706.7±349.8 RFU.For the 4 μL dilute blood mixed with mud guanidine salt chemical lysis,it cannot obtain complete STR loci after extraction and amplification.20 μL dilute blood mixed with mud guanidine salt was chemically cleaved and amplified to obtain complete STR loci with an average peak height of 1 899.8±801.3 RFU.After extraction and amplification by mud suspension instead of silica beads to extract 20 μL diluted blood DNA,complete STR loci were obtained.Conclusion Silicon dioxide in soil can bind to DNA in the presence of guanidine salts,leading to a decrease in the efficiency of recovering on-site biological evidence DNA using the silicon bead method.
ABSTRACT
Objective This exploratory study aimed to assess effectiveness with ethylene oxide treatment for removing DNA contamination. Methods 98 different spiked samples such as saliva, dander, skin cell, hair, blood and cartilage were conducted with ethylene oxide treatment. After extraction of samples, the dna was amplified and then the STR analysis was performed with 3130xl or 3500xl. Results A 6h EO treatment results showed that two saliva stains of 44 samples STR profile were detected; Just one hair of 54 samples treated with ethylene oxide was detected contaminating DNA with EO treatment for 8 hours. Conclusion This work suggested that it was more successful to reduce DNA contamination by using ethylene oxide treatment.
ABSTRACT
Objective To evaluate the forensic application of TE-MAGS technology based on magnetic beads kit on TECAN pipetting platform and establish the automated DNA extraction system of case work samples. Methods Sensitivity test: 10 different DNA samples from 0.1ng to 1ng were prepared with a commercial standard DNA 9947A diluted into 200μL TES. DNA samples were purified by the TE-MAGS technology automatically on the TECAN pipetting platform and then typed using the IdentifilerTM Kit and get the profile of STR with the software GeneMapper ID-X; the power of purification was tested with a trail that purified 1ng DNA mixed with humus acid and hemachrome. Comparative test: 304 casework samples were divided into two purified by TE-MAGS technology and silicon beads respectively to compare the power of purification and the possibility of forensic utility. Results Sensitivity test: 0.3ng and more imported DNA can obtain a good quality of DNA profile compared to the lower imported DNA with dropout of STR peaks (0.1ng and 0.2ng). The power of purification of the TE-MAGS technology was not affected by humus acid and hemachrome. The comparison result between automatic TE-MAGS technology and manual silicon beads extraction methods from 304 casework samples showed that the former's success rate(50%) was higher than the latter(40.8%). Conclusion The established DNA purification method of TE-MAGS technology automatic DNA extraction system in this study was obviously advantaging at the aspect of success rate, stability, and uniformity and suited to application in the forensic utility future.
ABSTRACT
Objective This study aimed to assess the efficiency and purification of the Trace DNA extraction with a quantified method for the magnetic bead-based DNA extraction as performed on the Tecan Automated systems with TE-MAGS magnetic separator. Methods Serial dilutions of standard commercial DNA 9947A were used with the total DNA contents, 0.1ng, 0.2ng,0.3ng, 0.4ng,0.5ng, 0.6ng, 0.7ng, 0.8ng, 0.9ng,1ng,diluted progressively and a 1ng DNA (standard commercial DNA 9947A) admixed with 6 common DNA-PCR inhibitors were extracted on the Automated systems and then performed via Fluorogenic probe quantitative PCR and STR genotype for the quantification analysis of recovery and purification. Results The recovery rate of standard 9947A DNA diluted with 0.1~1ng was 38.92~60.01%, and 0.3ng and more DNA could observed the full STR profiles. For the different PCR inhibitors, above 94.5% of bile acid, collagen and urea were efficient removal during the purification process, and the hemoglobin, melanin and humic acid removal efficiency were about 97.5%, 97.85%, 82.14%, respectively.Conclusion Our results suggested that The TE-MAGS magnetic bead-based DNA extraction was suitable for the extraction of trace DNA with high recovery efficiency and purification ability.