Multilayer nanoparticles with a magnetite core and a polycation inner shell as pH-responsive carriers for drug delivery.

Nanocarriers with multilayer core-shell architecture were prepared by coating a superparamagnetic Fe(3)O(4) core with a triblock copolymer. The first block of the copolymer formed the biocompatible outermost shell of the nanocarrier. The second block that contains amino groups and hydrophobic moiety formed the inner shell. The third block bound tightly onto the Fe(3)O(4) core. Chlorambucil (an anticancer agent) and indomethacin (an anti-inflammation agent), each containing a carboxyl group and a hydrophobic moiety, were loaded into the amino-group-containing inner shell by a combination of ionic and hydrophobic interactions. The release rate of the loaded drugs was slow at pH 7.4, mimicking the blood environment, whereas the release rate increased significantly at acidic pH, mimicking the intracellular conditions in the endosome/lysosome. This can be attributed to the disruption of the ionic bond caused by protonation of the carboxylate anion of the drugs and the swelling of the inner shell caused by protonation of the amino groups.