A Functionalized Graphene Oxide-iron Oxide Nanocomposite For Magnetically Targeted Drug Delivery,Photothermal Therapy, And Magnetic Resonance Imaging

Objective To study the feasibility of functionalized graphene oxide-iron oxide nanocomposite for magnetically targeted drug delivery, photothermal therapy, and magnetic resonance imagingMethods①Synthesize a multi-functional superparamagnetic graphene oxide-iron oxide hybrid nanocomposite (GO-IONP), which is then functionalized by a biocompatible polyethylene glycol (PEG) polymer to acquire high stability in physiological solutions and then the exosyndromes of the graphene oxide-iron oxide nanocomposite were evaluated.②A chemotherapy drug, doxorubicin (DOX), was loaded onto GO-IONP-PEG, forming a GO-IONP-PEG-DOX complex, which enables magnetically targeted drug delivery. Confocal images of GO-IONP-PEG-DOX incubated with4T1cells after6h were taken. Confocal images of Calcein AM/PI co-stained cells after being incubated with GO-IONP-PEG-DOX for24h with images taken right above the magnet and far from the magnet.③A magnet was placed under the cell culture dish during incubation. Confocal fluorescence images of calcein AM (green, live cells) and PI (red, dead cells) co-stained cells after magnetically targeted photothermal ablation with the images taken at three different locations in the culture dish.④T2-weighted MR images of4T1tumor-bearing mice with and without GO-IONP-PEG injection were taken24h after intravenous injection.⑤The tumors of tumor-bearing mices were irradiated by the808-nm laser at0.5W/cm2for5min,MR imaging was carried out right away. On the other hand, the tumor growth of control mice without laser irradiation was also conducted by MR images. Results①The resulting GO-IONP-PEG exhibited excellent stability in various physiological solutions including saline, cell medium and serum. The average diameter of nanoparticles was around50～300nm. Magnetization loops of GO-IONP-PEG indicates the superparamagnetic properties of GO-IONP-PEG. T2-weighted MR images of GO-IONP-PEG solutions acquired on a3-T MR scanner revealed the concentration-dependent darkening effect.②A maximal DOX loading of-220%by weight was obtained in the drug loading. DOX release from GO-IONP-PEG-DOX nanocomposite in buffers at pH5.0and7.4were50%and20%. While GO-IONP-PEG was not obviously toxic to cells even at very high concentrations, GO-IONP-PEG-DOX exhibited similar cytotoxicity to free DOX. Confocal fluorescence images detecting DOX fluorescence revealed the high uptake of GO-IONP-PEG-DOX by cells grown right above the magnet after6h of incubation. Calcein AM/PI double stained images of cells after24h of incubation further showed that the magnetically targeted drug delivery by GO-IONP-PEG-DOX was able to selectively kill cells that were localized close to the magnet, without affecting the viability of cells outside the magnetic field.③GO-IONP-PEG incubated cancer cells were largely killed after laser irradiation, showing decreasing cell viabilities as the laser power was increased, while the viabilities of untreated cells were not noticeably affected even under high power laser irradiation.④T2-weighted MR images of GO-IONP-PEG injected mice showed dramatic darkening effects in the tumor and liver areas, with signals significantly decreased by-67%and-64%respectively, as compared with untreated control mice.⑤For the treatment group, complete tumor elimination was observed by continuously monitoring the tumor development in photothermally treated mice by MR imaging. On the other hand, the tumor growth of control mice without laser irradiation was not affected as revealed by MR images and led to animal death within20days.Conclusion The GO-IONP-PEG was stable in physiological environments and exhibited no obvious in vitro toxicity to cells at the tested concentrations. Drug delivery and photothermal treatment targeted under a magnetic field was further realized using GO-IONP-PEG, achieving selective killing of cancer cells in highly localized regions. Last but not least, in vivo MR imaging of tumors in mice was also demonstrated using our GO-IONP-PEG as the T2contrast agent. Beyond that, we further use GO-IONP-PEG as a theranostics probe for in vivo MR imaging guided PTT treatment, and achieve ultra-efficient tumor ablation. Our study highlights the great potential of graphene-based functional nanocomposites for cancer theranostic applications.