Development of a controlled-release drug delivery system by encapsulating oxaliplatin into SPIO/MWNT nanoparticles for effective colon cancer therapy and magnetic resonance imaging

The development of a controlled-release drug delivery system has been an important objective for cancer therapy. To achieve the goal of sustained drug release for preventing the biotoxicity of platinum drugs, oxaliplatin was encapsulated into PEGylated multiwalled carbon nanotubes (MWNTs) decorated with superparamagnetic iron oxide (SPIO) for magnetic resonance imaging (MRI). The superparamagnetic properties and purification of SPIO/MWNT composites were achieved by annealing treatment during the fabrication process; the better hydrophilicity and biocompatibility were also accomplished subsequently after modification with polyethylene glycol (PEG). Oxa/MagMWNT-PEG 7 presented the ability of sustained release, as only 36.25% of loaded oxaliplatin leaked within 12 h and 55.48% lasted over 144 h. An in vitro study revealed that compared with free oxaliplatin and Oxa/MagMWNT 8, Oxa/MagMWNT-PEG 7 showed a slightly decreased cytotoxic effect when the cell viability was assessed at 12 and 24 h; however, a drastic enhancement in cytotoxicity was observed at 96 h. Platinum-DNA quantification on HCT116 cells showed that the internalization of oxaliplatin lasted up to 96 h, which was due to the sustained release of nanomedicine. An in vivo study showed that the nanomedicine-treated group exhibited effective antitumor efficacy similar to the free drug-treated group, but without inducing death in mice. After intravenous administration, the T-2-weighted MRI signal revealed that Oxa/MagMWNT-PEG7 had an excellent MRI enhancement in the tumor region. This SPIO-decorated MWNT composite encapsulated with antitumor drugs could potentially be useful for treatments, such as cancer therapy and MRI.