Electrostatic droplets assisted in situ synthesis of superparamagnetic chitosan microparticles for magnetic-responsive controlled drug release and copper ion removal

This paper demonstrates a facile approach for the in situ synthesis of size-controllable superparamagnetic chitosan micro-beads with a saturation magnetization value as high as ca. 35.3 emu g^-1 at room temperature. The proposed process utilized the electrostatic droplets (ESD) technique, which is quite effective in producing uniform-sized polymer beads. A sodium hydroxide solution was employed for both the solidification of chitosan and the co-precipitation of ferro-gels containing both ferrous and ferric cations. The diameter of the beads was very uniform (each relative standard deviation was below 3.4%) and adjustable from 84 μm to ca. 555 μm by varying the electrostatic field. Cell viability tests indicated that the superparamagnetic chitosan particles were eco-friendly and had a high potential for biological applications. The results show that the superparamagnetic chitosan particles achieved superior results in magnetic-responsive drug release as well as heavy metal removal (e.g. copper ions). This study demonstrated that the appropriate magnetic field intensity for different release patterns is predictable, which allows for better application of microcapsules as a smart drug carrier. In addition, the proposed chitosan particles serve as an alternative material for the adsorption of heavy metal ions from contaminated industrial effluents, while their superparamagnetic properties are advantageous in that they make the chitosan particles guidable by an external magnetic field.