pH-responsive superstructures prepared via the assembly of Fe 3 O 4 amphipathic Janus nanoparticles.

The strategy of using Fe3 O4 amphiphilic Janus nanoparticles (Fe3 O4 @AJNPs) bearing β-cyclodextrin (β-CD) and aminopyridine (APD) functionalized polymethyl methacrylate (PGMA) to construct pH-stimuli responsive co-assemblies through host-guest interactions between β-CD and APD was proposed. The spherical co-assemblies with an average diameter about 210 nm were excellent magnetic responsive and quite stable even up to 2 months in deionized water. The pH-liable capability of these co-assemblies was revealed by disassembly of the formed superstructures with destruction of the built inclusion complexes. The disassembly process was monitored by SEM, TEM, DLS and fluorescent molecules probe. After disassembly of the co-assemblies caused by protonation of nitrogens in APD, hydrophobic PGMA-APD lacking of interactions with the Fe3 O4 @AJNPs chains was precipitated, and the remained Fe3 O4 @AJNPs turned to re-assemble to self-assemblies. Besides, the recyclable Fe3 O4 @APJNs could reassembly with additional PGMA-APD to build co-assemblies with a uniform morphology for several times. These pH-sensitive co-assemblies with high stability, good magnetic responsiveness and cytocompatibility could be used as pH-responsive vehicles within which to encapsulate drugs for subsequent controlled release.