Albumin release from a brain-resembling superabsorbent magnetic hydrogel based on starch

Brain-resembling superabsorbent hydrogel composites were developed via UV-induced copolymerization-crosslinking of vinyl-modified starch with acrylic acid (AAc) and N,N-dimethylacrylamide (DMAAm) in the presence of Fe3O4 particles. The iodine test revealed the actual 3D network structure of starch within the swollen hydrogel composite. FTIR spectra of the hydrogel composites indicated interaction between the carboxyl groups from a hydrogel and the iron ions from Fe3O4. The formation of the hydrogel composites also was evidenced by wide-angle X-ray diffraction (WAXD) and energy dispersive X-ray (EDS) spectroscopies. Scanning electron microscopy (SEM) images revealed a homogeneous material since no phase separation between the hydrogel and the Fe3O4 phases could be observed. Minimal fragments of the swollen composite allowed the study of its actual morphology by TEM imaging. Stick-type structures were observed in the composite, as a result of a water-equilibrated structural configuration (obtained in a swollen state) of carboxyl groups of AAc coordinated to iron ions of Fe3O4. The albumin release mechanism of the hydrogel without Fe3O4 is governed by macromolecular relaxation. In the hydrogel composites, the albumin release was driven by macromolecular relaxation, but with a strong tendency to anomalous transport, because of both the tortuosity effect and attenuation of the anion–anion electrostatic repulsion forces. On the other hand, the albumin release became more dependent on anomalous transport with an applied magnetic field, which intensified the tortuosity effect. The proposed hydrogels are more appropriate for use as oral drug delivery systems because they provide a better sustention of the drug over the in vitro release experiment.