Synthesis and characterization of a novel multi-functionalized reduced graphene oxide as a pH-sensitive drug delivery material and a photothermal candidate

In this work, we describe a simple and effective method for the synthesis of a novel multi-functionalized reduced graphene oxide (rGO/DA/Au NPs/DOX) through the successive reaction of graphene oxide (GO) with dopamine (DA), HAuCl4/NaBH4 and doxorubicin (DOX) under mild conditions. The rGO/DA/Au NPs/DOX hybrid nano material was characterized by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDS), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV-visible absorption analyses, dispersion stability, zeta potential and dynamic light scattering (DLS) analysis. A good dispersion stability of rGO/DA/Au NPs/DOX material was observed with an average size of about 75 nm. The DOX loading capacity of rGO/DA/Au NPs was determined to be 0.852 mg/mg at an initial DOX concentration of 0.171 mg/ mL. Then, the rGO/DA/Au NPs/DOX was explored for DOX release under various pH values of 9.4, 7.4 and 5.4. It was found that the rate of DOX release from the rGO/DA/Au NPs/DOX hybrid nanomaterial was pH-dependent with a DOX release of 67% under acidic (pH = 5.4) conditions. Due to the different DOX release rates under different pH values, the multi-functionalized rGO can be used as a suitable candidate material for intelligent drug release. The photothermal properties of rGO/DA/Au NPs/DOX hybrid nanomaterial were assessed under simulated solar sun irradiation. A rapid increase of the temperature was recorded upon irradiation, suggesting that rGO/DA/Au NPs/DOX hybrid material has good potential as a new photothermal agent.