Photothermally Enhanced Drug Delivery by Ultrasmall Multifunctional FeCo/Graphitic Shell Nanocrystals

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Abstract
FeCo/graphitic carbon shell (FeCo/GC) nanocrystals (∼4−5 nm in diameter) with ultrahigh magnetization are synthesized, functionalized, and developed into multifunctional biocompatible materials. We demonstrate the ability of this material to serve as an integrated system for combined drug delivery, near-infrared (NIR) photothermal therapy, and magnetic resonance imaging (MRI) in vitro. We show highly efficient loading of doxorubicin (DOX) by π-stacking on the graphitic shell to afford FeCo/GC−DOX complexes and pH sensitive DOX release from the particles. We observe enhanced intracellular drug delivery by FeCo/GC−DOX under 20 min of NIR laser (808 nm) induced hyperthermia to 43 °C, resulting in a significant increase of FeCo/GC−DOX toxicity toward breast cancer cells. The synergistic cancer cell killing by FeCo/GC−DOX drug delivery under photothermal heating is due to a ∼two-fold enhancement of cancer cell uptake of FeCo/GC−DOX complex and the increased DOX toxicity under the 43 °C hyperthermic condition. The combination of synergistic NIR photothermally enhanced drug delivery and MRI with the FeCo/GC nanocrystals could lead to a powerful multimodal system for biomedical detection and therapy.