Design of yolk-shell Fe3O4@PMAA composite microspheres for adsorption of metal ions and pH-controlled drug delivery

Core-shell-shell structured Fe3O4@SiO2@PMMA composite microspheres were synthesized on a large scale by combining sol-gel reaction and seeded emulsion polymerization. The yolk-shell structured Fe3O4@PMAA microspheres with pH-responsive shells were then produced by the hydrolysis reaction of the PMMA shells in NaOH aqueous solution during etching of the silica interlayers. The resulting microspheres, with tunable void space and shell thickness, were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and dynamic laser scattering (DLS). The effect of shell thickness and void space of the yolk-shell Fe3O4@PMAA microspheres on the adsorption of metal ions and drug delivery was investigated. The results demonstrated the excellent adsorption capacity of Cu2+ and Pb2+ and reusability for Cu2+ using the optimum Fe3O4@PMAA microspheres as adsorbents under weakly acidic conditions, as well as the high loading capacity and pH-controlled release ability of yolk-shell Fe3O4@PMAA microspheres by loading ceftriaxone sodium and performing a controlled release study.