A method based on amino-modified magnetic nanoparticles to extract DNA for PCR-based analysis.

DNA extraction using magnetic particles (MPs) is a simple and rapid process. MPs directly combine with DNA, thereby facilitating removal of impurities in complex samples by magnetic attraction. Amino-modified magnetic nanoparticles (AMNPs) have been described as poor substrates for DNA extraction because it was difficult to desorb DNA from the AMNPs for downstream assays. In this study, we proposed to use the complexes of AMNPs and DNA directly as templates for PCR, thereby bypassing the difficulty of desorbing DNA from AMNPs. At first, we compared three distinct chemical modifications for magnetic nanoparticles (hydroxyl modified-, carboxyl modified-, and amino modified-magnetic nanoparticles) for the extraction of DNA under experimental conditions compatible with downstream assays (e.g., PCR). Under such conditions, we demonstrated that only the AMNPs had a powerful adsorption capability for DNA with 98% separation rate. We directly employed the complexes of AMNPs and extracted DNA as templates for PCR, which reduced the separation steps and minimized the loss of DNA. Notably, we minimized AMNPs-caused inhibition of the PCR by adding BSA to the PCR mixture. The AMNPs extraction was successfully applied for the detection of a genetically modified organism, species identification, and an allergen in a heterogenous mixture. The AMNPs-based extraction method is a simple and rapid process to extract DNA and even trace amounts of DNA for PCR-based analysis.