Facile control of porous structure of graphene aerogel via two-step drying process and its effect on drug release

A facile method has been proposed for synthesizing graphene aerogels with controllable pore structures using a combination of hydrothermal reaction and controlled drying process. The hydrothermally synthesized graphene hydrogel was partially dried under mild hot air conditions in a convection oven, and then completely dehydrated by freeze-drying. The resulting graphene aerogels had a three-dimensionally interconnected porous structure with both mesopores and macropores, which consisted of thin layered walls stacked with graphene sheets. Controlling hot air drying time could regulate various porous structural properties because the mesopore size, surface area, macropore size, and bulk density were linearly correlated to the hot air drying time. When ibuprofen was loaded into the graphene aerogel as a model drug, its release profile was finely controlled by the hot air drying time. The application of the hydrophilic drug, diclofenac sodium, also showed the similar release behavior as that of hydrophobic ibuprofen. According to the Korsmeyer–Peppas law, the release of ibuprofen from graphene aerogel was predominantly governed by Fick’s law of diffusion. The diffusion coefficient calculated by applying the Higuchi relationship was inversely proportional to the logarithmic time of hot air drying. The cytotoxicity test further confirmed that the graphene aerogels synthesized in this study were highly biocompatible for local drug release. These findings demonstrated the suitability of our method for controlling the porous structure of graphene aerogels and regulating the release of drugs from graphene aerogels.