Double-walled hollow polymeric microspheres with independent pH and temperature dual-responsive and magnetic-targeting function from onion-shaped core-shell structures.

The magnetic-targeting stimuli-responsive hollow polymeric microspheres show unique performance as the intelligent carriers for the site specific controlled delivery of drugs or genes. In the work, the well-defied dual-responsive double-walled hollow microspheres with movable magnetic cores were prepared from the penta-layer onion-shaped core-shell microspheres. Their double-walled shells were independent, with the pH-responsive crosslinked poly(methacrylic acid) (PMAA) layer as the inner shell and the temperature responsive crosslinked poly(N-isopropylacrylamide) (PNIPAM) layer as the outer shell. The combination of the pH and temperature dual-responsive and the magnetic-targeting function make the hollow microspheres to be the most promising intelligent carriers in the biomedical fields.