Synthesis and characterization of fluorescent magnetic nanoparticles: a dual-function platform for DNA separation and real-time visualization

Multifunctional magnetic nanoparticles have become the subject of significant attention in biomedical applications recently, especially for their applications in the separation and detection of biomolecules. This study focuses on the preparation of dual-functional iron oxide magnetic nanoparticles (Fe₃O₄ MNPs) conjugated with a fluorescent dye for facilitating real-time tracing and visualization of DNA molecules during a separation process. The fluorescent Fe₃O₄@SiO₂@FITC nanoparticles were used both for the separation of DNA molecules from a solution by applying an external magnetic field and for quantification by analyzing the fluorescence properties of the nanoparticles upon DNA binding. The pH of the solution was optimized to achieve the best adsorption efficiency using the proposed method. Approximately 91% adsorption efficiency was achieved using fluorescent Fe₃O₄@SiO₂@FITC MNPs at a pH of 4.44 with a recovery of ∼50% at the same pH, while amine functionalized Fe₃O₄@SiO₂-NH₂ MNPs exhibited lower adsorption efficiencies at every pH of the medium (maximum ∼89% at a pH of 4.44 and minimum ∼52% at a pH of 11.01). The ultraviolet-visible (UV-Vis) and fluorescence emission spectra showed that the increasing number of DNA molecules adsorbed on the Fe₃O₄@SiO₂@FITC MNPs led to a gradual decrease in the absorption and fluorescence emission intensity, indicating the presence of DNA molecules. This study highlights the potential of fluorescent MNPs as a dual-function platform, combining magnetic separation and fluorescence-based real time monitoring of DNA.