Thermoresponsive polymer brush-functionalized magnetic manganite nanoparticles for remotely triggered drug release

A thermoresponsive hybrid system for drug delivery purposes is designed by modifying the surface of silica-coated magnetic lanthanum strontium manganite nanoparticles with block copolymers following a non-covalent approach. Block copolymers containing a short poly(L-lysine) segment and a polyether segment of varying composition are adsorbed through electrostatic interactions between positively charged lysine units and negatively charged SiO- groups at the silica surface, giving rise to mixed polyether brushes with a good control over the chain surface density and thickness of the polymer layer. The thermoresponsiveness of the assemblies is controlled by the ethylene oxide/propylene oxide ratio in the polymer brush and the corresponding LCST of the polyether blocks. Important parameters like the aggregation temperature of the particles can be finely adjusted by modifying this ratio. The polarity of the polymer layer can also be varied to maximize the encapsulation efficiency of a moderately hydrophobic drug like doxorubicin. Drug release experiments are performed by taking advantage of the ac magnetically induced heating properties of the magnetic core to speed up the release of doxorubicin owing to structural changes within the polyether brush.