Facile synthesis of Ca-crosslinked sodium alginate/graphene oxide hybrids as electro- and pH-responsive drug carrier.

The design of stimuli-responsive drug carrier for controlled drug release is of significant importance in pharmaceutics, medicine and biology. Here, sodium alginate (SA) was integrated with graphene oxide (GO) by using Ca as the crosslinker. The resultant SA-Ca-GO composites were freeze-dried to produce SA-Ca-GO hybrids, which were then examined by Fourier transform infrared (FT-IR) spectrometry, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The SA-Ca-GO hybrids were used as the drug carrier of methotrexate (MTX), and electro- and pH-responsive release of MTX was successfully achieved due to the excellent conductive ability of GO and the pH-sensitive property of SA. Finally, Higuchi model was employed to investigate the release kinetics of MTX from the SA-Ca-GO hybrids, and the results indicate that the release of MTX is controlled by Fickian diffusion.