Chitosan core-corona nanospheres: A convenient material to tailor pH and solvent responsive magnetic nanoparticles

Chitosan nanospheres (CSNS) with a core-corona structure containing hydrophobic phthaloyl group and a hydrophilic poly(ethylene glycol) group perform as the backbone to allow interaction with magnetic nanoparticles (MAG). Having hydrophilic corona favors the coverage of MAG on the CSNS surface to form CSNS–MAG. In contrast, having hydrophobic core allows the incorporation with MAG if the MAG is in the form of oleic acid coated MAG (O–MAG) to form CSNS–O–MAG. In the case of CSNS–MAG, the dispersion of MAG on the CSNS surface is easily tunable and at that time the MAG content on CSNS is also variable under pH condition, so-called pH responsive CSNS–MAG. The CSNS–MAG is well-dispersed and stabilized in colloidal state in aqueous and polar solvent and this brings to the size adjustable CSNS–MAG, so-called solvent responsive CSNS–MAG. The present work shows how core-corona chitosan is a convenient material to hybridize with MAG not only because it allows the interaction either with the hydrophilic MAG or with the hydrophobic MAG (i.e. O–MAG), but also because it provides the selective conditions to control the MAG content as well as the stability of the nanospheres in the media.