Magnetic Nanoparticle-Based DNA Isolation from Refined Soybean Oil: A Cost-Effective Approach for GM Testing

Soybean oil has recently emerged as the most widely consumed genetically modified (GM) vegetable oil globally. DNA-based methods offer considerable advantages for monitoring GM-derived products; however, their efficacy strongly depends on the quality and quantity of extracted DNA. Owing to intensive processing, refined oils typically contain extremely low concentrations of severely fragmented DNA, making DNA extraction highly challenging. To address this issue, we introduce an innovative magnetic bead-based DNA extraction protocol specifically tailored to refined soybean oils. Optimal DNA adsorption was achieved using 300 nm carboxyl (-COOH)-modified magnetic beads under optimized conditions, including 1 M guanidine isothiocyanate (GITC) buffer at pH 6.0, combined with ethanol at a 1:1 ratio. Subsequently, we developed a cetyltrimethylammonium bromide (CTAB)-magnetic bead method in which DNA was efficiently transferred from the oil phase to the aqueous phase, concentrated via precipitation, resuspended in GITC buffer, and finally purified using magnetic beads. Comparative evaluations using nested polymerase chain reaction (PCR) and real-time PCR confirmed that this method significantly outperformed traditional CTAB-based methods (CTAB alone, CTAB-hexane) and two representative silica membrane-based extraction kits. Spike recovery experiments further demonstrated its superior efficacy, achieving a DNA recovery rate of 76.37%. The proposed protocol is simple, user-friendly, cost-effective, and highly efficient, markedly reducing reliance on large volumes of organic solvents (e.g., hexane and chloroform) and minimizing the required centrifugation steps. This novel method established an effective approach for DNA extraction from refined vegetable oils, facilitating the development of rapid and reliable GM detection.