Graphene oxide decorated diatom silica particles as new nano-hybrids: towards smart natural drug microcarriers†
Herein, we demonstrate the fabrication of a novel nano-hybrid material based on diatom silica microparticles from diatomaceous earth (DE) and graphene oxide (GO). Two different approaches for the fabrication of nano-hybrids were used, including covalent coupling of GO sheets onto the diatom surface and electrostatic attachment. Covalent attachment was carried out through a facile amine coupling strategy via activation of carboxyl groups on GO, followed by covalent attachment to amine terminal groups of 3-aminopropyl-triethoxysilane (APTES) functionalized DE particles. Electrostatic attachment of GO (i.e. negatively charged) was carried out on positively charged APTES functionalized DE particles. The GO decorated DE nano-hybrids prepared with both the fabrication processes were extensively characterized by SEM, TEM, FTIR, and Raman spectroscopy to confirm the new chemical composition and structure. The application of the GO–DE nano-hybrid as a smart pH sensitive micro-drug carrier at pH 7.4 and pH 3.5 was demonstrated using a model drug, indomethacin (IMC). Finally, the drug release data were fitted to zero-order and Korsmeyer–Peppas models to understand the mechanism of drug release.