Dna Purification Of Forensic Samples Based On Magnetic Particles

The forensic DNA typing is often difficult, because the samples are easily affected by physical and chemical factors, which could lead to the damage of DNA molecules and DNA strand. However, these samples are often the most important clue to the criminal investigation. So the DNA extraction has become the key point, and also the "bottleneck" in forensic DNA typing. Therefore, the high performance DNA purification method plays a crucial role in forensic DNA typing. Currently, the main methods of DNA purifications are phenol-chloroform, Chelex-100 and magnetic separation method。Comparing with phenol-chloroform and Chelex-100, the magnetic separation method has a advantage of centrifugation free,easy operation and no pollution, as well as support the automatic equipments to achieve the high-throughput purification. Magnetic separation technology is based on the magnetic particles which are the carriers, and the function groups of magnetic material can be used for specific absorption of DNA, making the DNA bound to the surface of magnetic particles, under the effect of outer magnetic the purpose of separation and purification of DNA is achieved.In this study, the silica magnetic particles are used as the carrier, the dry blood spot as the experimental samples. The Method of DNA Purification from dry blood spots was established by optimizing the samples from breaking,DNA binding,washing and eluting, and then fluorescence quantitative of DNA. The CV(coefficients variation) within a lot, the CV among the different lots were calculated, which were used to evaluate the stability for this method. Finally, this method was compared with commercial kits, and the isolated DNA was tested by downstream PCR-STR genotyping. The result showed that the 50-70ng of DNA were got from 5mm dry blood spot, the CV within a lot is 9.23%, the CV among the different lots is 12.36%. This method can reach the level of similar products and could meet the needs of downstream PCR-STR genotyping without PCR inhibitor in the whole purification process. This method was applied for purification of saliva,nails,cigarette butts,hair,swabs and other trace DNA samples, the PCR-STR result showed that all 16 sites were amplified. Generally, the method is suitable for purification of various forensic samples and could achieve a better results of DNA typing.