Understanding the pH dependent fluorescence and doxorubicin release from graphene oxide functionalized citric acid dendrimer as a highly efficient drug delivery system

Abstract

In this work, the third generation of a dendrimer based on citric acid and 1, 3, 5 benzene tricarbonyl trichloride, as a core (G3), was synthesized to modify graphene oxide (GO) surface. A novel graphene oxide hybrid (GO-G3) with green fluorescent in an acidic medium (pH 4) was developed to track its interaction with cancer and healthy cell lines as a potential drug carrier. GO-G3 is highly fluorescent due to hydrogen bonding that passivates the electron-hole recombination process. The interaction among G3 dendrimer and GO surface was investigated at two pH in detail as the main cause for observation of such pH-dependent fluorescent in acidic media. The functionalized GO were studied carefully and characterized by multiple techniques such as fluorescence spectroscopy; SEM (scanning electron microscope); TEM (Transmission electron microscopy), FT-IR (Fourier transformed infrared spectroscopy); XRD (X-ray diffraction spectroscopy); XPS (X-ray photoelectron spectroscopy), DLS (Dynamic light scattering), AFM (atomic force microscopy); UV-Vis absorption spectroscopy, Raman spectroscopy and CLSM (Confocal laser scanning microscopy). The synthesized dendrimer displayed no emission under a UV lamp. However, after the functionalization of the GO surface with G3 dendrimer, green photoluminescence was detected at 471 nm. G3 dendrimer covers GO surface and prevents both GO sheets restacking and also electron-hole recombination process that consequently led to the observation of pH-dependent photoluminescence (PL). The drug encapsulation capacity of hybrid for doxorubicin (DOX) drug was 159.48% and also, the drug release profile of GO-G3/DOX hybrid indicated a pH-dependent release with more preference for drug discharge in acidic media. Furthermore, the cytotoxicity investigation of GO-G3/DOX against T47D cells (human breast cancer cells) indicated the IC50 value of 12.02 μg/ml.