Extraction of Genomic DNA from Soil Samples by Polyethylene Glycol-Modified Magnetic Particles via Isopropanol Promotion and Ca²⁺ Mediation

Obtaining reliable and informative DNA data from soil samples is challenging due to the presence of interfering substances and typically low DNA yields. In this work, we prepared poly(ethylene glycol)-modified magnetic particles (PEG@Fe₃O₄) for DNA purification. The particles leverage the facilitative effect of calcium ions (Ca²⁺), which act as bridges between DNA and PEG@Fe₃O₄ by coordinating with the phosphate groups of DNA and the hydroxyl groups on the particles. The addition of 2-propanol further enhances this Ca²⁺-mediated DNA adsorption by inducing a conformational change from the B-form to the more compact A-form of DNA. PEG@Fe₃O₄ demonstrates a DNA adsorption capacity of 144.6 mg g^-1. When applied to the extraction of genomic DNA from soil samples, PEG@Fe₃O₄ outperforms commercial kits and traditional phenol-chloroform extraction methods in terms of DNA yield and purity. Furthermore, we developed a 16-channel automated DNA extraction device to streamline the process and reduce the extraction time. The successful amplification of target bacterial and fungal amplicons underscores the potential of this automated, device-assisted method for studying soil microbial diversity.