Fe3O4-Capped Mesoporous Silica Foam for pH-Responsive Drug Delivery

In this work, Fe3O4 nanoparticles (NPs) capped mesoporous silica foam (MSF) was synthesized and proposed as a pH-responsive drug delivery system. Both Fe3O4 nanoparticles and mesoporous silica foam with uniform size and structures were prepared and functionalized by thiol-group. Rhodamine B, a typical dye, and doxorubicin (DOX), a typical chemotherapeutic agent, are used as drug models to be entrapped into nanopores of the thiol-modified MSF. The formation of disulfide bond between thiol-modified Fe3O4 nanoparticles and thiol-functionalized MSF led the Fe3O4 NPs capped onto MSF, which blocked the release of the drugs from the nanopores of MSF. Due to the competitive combination with the ligand O atom derived from carboxylic group between metal Fe and protons (H+) in lower pH, it was possible to break Fe-O coordination and realized a pH-responsive release system. The UV-visible spectrometric measurements show that trapped Rhodamine B cannot release form MSF within 70 hours when the pH of the solution is above 5.0, while it releases fast at pH below 5.0 due to the breaking of Fe-O coordination. Cytotoxicity tests show that DOX could not release from MSF@DOX@Fe3O4 after being blocked with Fe3O4 NPs, and made the HepG2 cells alive in the presence of MSF@DOX@Fe3O4. Therefore, the proposed drug carrier and pH-responsive system offered the possibility of biomedical applications in drug-controlled delivery.