Graphene-polyglycerol-curcumin hybrid as a near-infrared (NIR) laser stimuli-responsive system for chemo-photothermal cancer therapy

The aim of this study is to develop a nano graphene-polyglycerol-curcumin hybrid capable of simultaneous co-delivery of chemotherapeutic drug and cytotoxic heat to cancer cells by near infrared (NIR) laser irradiation. Based on a fluorescence quenching study, the nano graphene sheet was functionalized by a polyglycerol polymer via pi-pi interaction between the pi conjugated system of graphene and the aromatic focal point of polyglycerol through static mechanism. The binding constant and standard Gibbs free energy change of the binding process, obtained from isothermal titration calorimetry (ITC), were 1.8 x 10(6) M-1 and -35.7 kJ mol(-1), respectively. This hybrid showed excellent heat generation efficiency (Delta T approximate to 60 degrees C in 5 min, 1 W cm(-1) NIR laser) and high loading capacity of curcumin (61%). The resulting drug delivery system displayed a good stability with low drug release in PBS. However, NIR laser irradiation could trigger release of curcumin from the surface of the functionalized graphene sheet in PBS (up to 5-fold greater release) due to the local generated heat. Also the laser induced intracellular release of curcumin was confirmed by flow cytometry analysis. So the combination of chemo/photothermal therapy using this advanced drug delivery system demonstrated a synergistic effect for killing of MCF-7 breast cancer cells by MTT and apoptosis assays.