Strategies Towards Submicron Size and High-Performance Magnetic PGMA@Fe3O4@SiO2–COOH Microspheres with Biological Application

The separation of target substances is a significant biological detection procedure, where magnetic microspheres can act as high-performance separation materials. However, challenges are still kept to fulfill all the requirements. A submicron magnetic poly (glycidyl methacrylate) (PGMA) microsphere was synthesized in this investigation by utilizing three distinct techniques: in situ coprecipitation, electrostatic self-assembly, and silica surface coating. The PGMA microspheres were initially produced through a soap-free emulsion polymerization technique, wherein the coagulation process was governed by surface charge density. This factor additionally impacted the size and monodispersity of the microspheres. Then, we discovered that the capping agent sodium citrate (Na3Cit) effectively regulated the superparamagnetism properties of magnetic microspheres; the critical size of the superparamagnetic was 10.9 nm. Furthermore, the concentration of Fe2+ and Fe3+ effectively regulated the saturation magnetization, a property that correlated with the nucleation rate of the Fe3O4 crystal. Additionally, we demonstrated that the pH regulated the electrostatic self-assembly, and it was suggested that positively charged PGMA–NH2 microspheres and negatively charged Fe3O4 nanoparticles be tightly coupled. For application, the PGMA@Fe3O4 microspheres were subsequently coated with SiO2, which had been surface-modified with carboxyl groups. The PGMA@Fe3O4 and carboxyl-modified microspheres exhibited saturated magnetization values of 23.73 and 17.73 emu/g, respectively. These microspheres have been effectively utilized for the extraction of DNA from various sources such as Salmonella typhi, monkeypox virus, and clinical swab samples, suggesting the potential of these microspheres for nucleic acid separation in the biomedical domain.