Synergistic effects of graphene quantum dots nanocarriers and folic acid targeting agent on enhanced killing of breast cancer cells by tamoxifen

In this study, a new targeted and controlled‐release drug delivery system based on graphene quantum dots (GQDs) was fabricated. The fluorescent GQDs were synthesized via an environmentally‐friendly chemical oxidation method, using graphene oxide (GO) as a precursor and hydrogen peroxide and ammonia solution as oxidants. Folic acid (FA), as a targeting agent, was bound to GQDs through strong amide covalent bindings, and tamoxifen (TMX), as a hydrophobic anticancer drug, was non‐covalently attached to the nanocarrier via π–π stacking bonds. The as‐prepared GQDs and TMX/FA‐GQDs were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectroscopy (UV/Vis), and photoluminescence spectroscopy (PL). The resulting TMX/GQDs demonstrated pH‐sensitive release behaviour with an overall release of 85% and 58% at pH 5.5 and 7.4, respectively, after 120 h. Also, the MTT assay test performed on MCF‐7 cells presented negligible toxicity of the nanocarriers, even at high concentrations. At the same time, the targeted nanocarrier, TMX/FA‐GQDs, showed much more toxicity towards MCF‐7 cells than the non‐targeted one and free TMX. The schematic shows pH‐sensitive release behaviour of GQDs loaded by TMX (TMX/GQDs) and higher cytotoxicity of GQDs functionalized with FA and loaded by TMX (TMX/FA‐GQDs) than the non‐functionalized one.