ABSTRACT
OBJECTIVES@#To compare the effects of cell lysis method and magnetic beads method in forensic DNA identification and to explore these two methods in forensic DNA identification.@*METHODS@#The genome DNA of THP-1 cells in different quantities was extracted by the cell lysis method and magnetic beads method, and the DNA content was quantified by real-time quantitative PCR. The cell lysis method and magnetic beads method were used to type the STR of human blood with different dilution ratios.@*RESULTS@#When the numbers of THP-1 cell were 100, 400 and 800, the DNA content extracted by cell lysis method were (1.219±0.334), (5.081±0.335), (9.332±0.318) ng, respectively; and the DNA content extracted by magnetic beads method were (1.020±0.281), (3.634±0.482), (7.896±0.759) ng, respectively. When the numbers of THP-1 cells were 400 and 800, the DNA content extracted by the cell lysis method was higher than that by the magnetic beads method. The sensitivity of cell lysis method and magnetic beads method was similar in STR typing of human blood at different dilution ratios. Complete STR typing could be obtained at 100, 300 and 500-fold dilutions of blood samples, but could not be detected at 700-fold dilution. STR typing of undiluted human blood could not be detected by cell lysis method.@*CONCLUSIONS@#The cell lysis method is easy to operate and can retain template DNA to the maximum extend. It is expected to be suitable for trace blood evidence tests.
Subject(s)
Humans , Forensic Medicine , DNA/genetics , Real-Time Polymerase Chain Reaction , Magnetic Phenomena , DNA Fingerprinting/methods , Microsatellite RepeatsABSTRACT
Objective To compare the effects of TRIzol and magnetic beadsmethods on quantitative detection of hepatitis C virus (HCV) RNA. Methods Serum samples and genotype information of 117 patients with positive HCV infection were collected. HCV RNA was extracted from serum samples by TRIzol method and magnetic bead method, respectively. And then the viral load of HCV RNA was detected by quantitative PCR to compare the difference between the two methods. Results qPCRresults showed that a good linear correlation existed between TRIzol and magnetic beads methods: y=0. 978x+0. 063 (R2=0. 973). Bland-Altman statistical analysis showed that the average logarithmic value of viral load ofHCV RNA extracted by TRIzol method was slightly lower than that of magnetic beads method, without significant difference (P>0. 05). There were no significant difference among the genotypes 1a, 1b, 2a, 3a or 6a between the two methods (P>0. 05). Conclusion TRIzol method is comparable to magnetic beads method in HCV RNA quantitative detection, with less samplevolume and lower cost, indicating that t might be widely used for developing ktt and HCV RNA clinical detection in China.
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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.
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Objective To compare and evaluate different DNA extraction methods for batches of bloodstain samples during the establishment of national DNA database. MethodsDNA was extracted from bloodstain samples collected for the establishment of DNA database using manual Chelex-100, Biomek 3000 automation workstation with Chelex-100 and DNA-IQTM magnetic bead method respectively, and the quantity of DNA was determined by the real-time fluorescent quantitative PCR technique. Genotyping was performed using the AmpFLSTR STR Identifiler kit and 3100 genetic analyzer. ResultsThe concentrations of DNA templates obtained by manual Chelex-100, automatic Chelex-100 and DNA-IQTM magnetic bead method were 0.593?0.131ng/?l, 0.579?0.096ng/?l and 0.447?0.056ng/?l respectively, and the success rates of genotyping with these DNA templates were 100%, 98.9% and 99.5% respectively. ConclusionThe automatic Chelex-100 method proposed by this study can be applied in the establishment of large-scale DNA databases.