One-pot hydrothermal synthesis of polyethyleneimine-coated magnetic nanoparticles for high-efficient DNA extraction of pathogenic bacteria

For separation of deoxyribonucleic acid (DNA), positively charged amino-modified magnetic nanoparticles (MN) can effectively adsorb negatively charged DNA through electrostatic interaction. However, the reported preparation of amino-modified MN is usually tedious and time-consuming. Therefore, a simple synthesis method of amino-modified MN is necessary for DNA extraction. Herein, a novel polyethyleneimine-coated MN (PMN) was fabricated by one-pot hydrothermal synthesis for high-efficient DNA extraction. The fabricated PMN showed numerous exposed amino groups, which not only could effectively capture DNA through electrostatic interaction, but also limited the aggregation of PMN during application. Under optimized adsorption conditions, the maximum adsorption capacity of PMN for DNA could reach 192.4 μg m g^-1. Shigella flexneri (S. flexneri) has the highest mortality rate among Shigella species and has been selected as target model pathogenic bacteria. Based on the optimized extraction conditions, PMN-based magnetic solid-phase microextraction (MSPE) and quantitative real-time PCR (qPCR) were integrated for detection of S. flexneri. The limit of detection of the proposed strategy was 2.4 × 10² CFU mL^-1 and obviously lower than the commercial kit. To prove the practicability, the PMN-based MSPE combined qPCR strategy was successfully used in the determination of S. flexneri in spiked real sample, and the recovery values were in the range of 95.1 % to 102.1 % for apple juice, 60.4 % to 85.7 % for pickled vegetable, 97.8 % to 99.5 % for pig liver and 95.1 % to 102.1 % for pig colon, respectively. Therefore, we believe that the resultant PMN have great potential to become a universal magnetic adsorbent for high-efficient DNA extraction from complex biological samples.