Water transport properties through starch-based hydrogel nanocomposites responding to both pH and a remote magnetic field

Abstract

This work reports the preparation of starch-based hydrogel nanocomposites that undergo changes in swelling behavior in response to both pH and a remotely applied magnetic field. The hydrogels were formed by ultrasound-induced radicalar cross-linking/polymerization of vinyl-modified starch with N′,N′-dimethylacrylamide (DMAAm) and acrylic acid (AAc) in the presence of CoFe2O4 nanoparticles (average diameter of 365.5 ± 2.1 nm). Water transport properties were studied by applying swelling-based kinetic models. The effect of the magnetic field on the swelling potential was more prominent at pH 2 for hydrogel without AAc and the ionic nature of the polymer network was more important at pH 10 for hydrogel with AAc. At pH 2, the swelling mechanism for all hydrogels is described by a pseudo-Fickian transport, and is independent of the applied magnetic field. At pH 7 and pH 10, the hydrogels containing AAc showed anomalous mechanism, attributed to the anion–anion electrostatic repulsion forces. These hydrogels showed an increase in the swelling rate at higher pH. A significant increase in the swelling rate was also observed when the magnetic field is on, but this was verified only at pH 2. The hydrogels made of starch (0.5%), DMAAm (0.25%), and CoFe2O4 (0.125% or 0.250%) underwent changes in swelling rate in response to an applied magnetic field, independently of pH. For these hydrogels, the magnetic properties of the nanoparticles were more important than their physical–chemical characteristics. Cytotoxicity research showed that the hydrogels have a great pharmacological potential for application in biological systems.