Magnetic iron oxide–fluorescent carbon dots integrated nanoparticles for dual-modal imaging, near-infrared light-responsive drug carrier and photothermal therapy

Abstract

Multifunctional hybrid nanoparticles (NPs, ∼100 nm) that combine magnetic Fe₃O₄ nanocrystals and fluorescent carbon dots (CDs) in porous carbon (C) were successfully synthesized using a one-pot solvothermal method by simply increasing the H₂O₂ concentration. The resultant Fe₃O₄@C-CDs hybrid NPs not only demonstrate excellent magnetic responsive properties (M_s = 32.5 emu g⁻¹) and magnetic resonance imaging ability (r^*₂ = 674.4 mM⁻¹ s⁻¹) from the Fe₃O₄ nanocrystal core, but also exhibit intriguing photoluminescent (quantum yield ∼6.8%) properties including upconversion fluorescence and excellent photostability from the CDs produced in the porous carbon. The hybrid NPs can enter the intracellular region and illuminate mouse melanoma B16F10 cells under different excitation wavelengths. Meanwhile, the mesoporous carbon shell and hydrophilic surface functional groups endow the hybrid NPs with high loading capacity (835 mg g⁻¹) for the anti-cancer drug doxorubicin and excellent stability in aqueous solutions. More importantly, the hybrid NPs can absorb and convert near-infrared (NIR) light to heat due to the existence of CDs, and thus, can realise NIR-controlled drug release and combined photothermo/chemotherapy for high therapeutic efficacy. Such nanostructured Fe₃O₄@C-CDs hybrid NPs demonstrate great promise towards advanced nanoplatforms for simultaneous imaging diagnostics and high efficacy therapy.