Positively charged graphene/Fe₃O₄/polyethylenimine with enhanced drug loading and cellular uptake for magnetic resonance imaging and magnet-responsive cancer therapy

Enhanced cellular uptake efficiency of nanoparticles is important for their biomedical applications, including photothermal therapy (PTT) for cancer. In this study, a one-pot method was used to construct a positively charged and magnet-responsive nanocomposite comprising reduced graphene oxide anchoring iron oxide (RGI) with a polyethylenimine (PEI) modification, to improve the efficiency of cell internalization. The surface charge can be finely tuned using PEIs of different molecular weights. The obtained RGI_1.8k composite (RGI modified by 1.8 kDa PEI) could load indocyanine green (ICG) at a high mass ratio of 10:3 and ablate cancer cells using low-density laser irradiation because of its positively charged surface. In addition, the hybrids of RGI_1.8k and ICG could kill most cancer cells at a laser density of 0.7 W/cm² in vitro and 0.3 W/cm² in vivo. At the same time, cell viability could be controlled by converting the external magnetic-field direction because of the enrichment of the magnet-responsive composite in vitro and in vivo. Furthermore, RGI_1.8k-ICGs could be used as T₂-weighted magnetic resonance and infrared thermal imaging agents. Coupled with the magnetic target effect, the imaging signal could be improved significantly. Therefore, RGI_1.8k-ICGs represent a new highly efficient PTT and imaging agent with great potential for cancer treatment.