Receptor-targeted, drug-loaded, functionalized graphene oxides for chemotherapy and photothermal therapy

Abstract

Cancer is one of the leading causes of death worldwide. Although different chemotherapeutic agents have been developed to treat cancers, their use can be limited by low cellular uptake, drug resistance, and side effects. Hence, targeted drug delivery systems are continually being developed in order to improve the efficacy of chemotherapeutic agents. The main aim of this study was to prepare folic acid (FA)-conjugated polyvinyl pyrrolidone-functionalized graphene oxides (GO) (FA-GO) for targeted delivery of sorafenib (SF). GO were prepared using a modified Hummer’s method and subsequently altered to prepare FA-GO and SF-loaded FA-GO (FA-GO/SF). Characterization of GO derivatives was done using ultraviolet/visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy, zeta potential measurements, and determination of in vitro drug release. Hemolytic toxicity, in vitro cytotoxicity, cellular uptake, and apoptotic effects of FA-GO/SF were also investigated. The results revealed that GO was successfully synthesized and that further transformation to FA-GO improved the stability and SF drug-loading capacity. In addition, the enhanced SF release under acidic conditions suggested possible benefits for cancer treatment. Conjugation of FA within the FA-GO/SF delivery system enabled targeted delivery of SF to cancer cells expressing high levels of FA receptors, thus increasing the cellular uptake and apoptotic effects of SF. Furthermore, the photothermal effect achieved by exposure of GO to near-infrared irradiation enhanced the anticancer effects of FA-GO/SF. Taken together, FA-GO/SF is a potential carrier for targeted delivery of chemotherapeutic agents in cancer.

Keywords:

• graphene oxide
• folic acid
• sorafenib
• targeted drug delivery
• near-infrared

Supplementary materials

Figure S1 Characterization of the prepared GO.

Notes: (A) Digital image of GO in suspension and in a freeze-dried form. UV spectra (B), FTIR spectroscopy (C) and XRD analyses (D) of graphite and GO.

Abbreviations: FTIR, Fourier transform infrared; GO, graphene oxide; au, arbitrary unit; UV, ultraviolet; XRD, X-ray diffraction.

Figure S2 Stability of GO (A and B) and FA-GO/SF (C and D) in the indicated media.

Notes: (A and C) 5 minutes and (B and D) 24 hours after preparation.

Abbreviations: FA, folic acid; GO, graphene oxide; PBS, phosphate-buffered saline; FBS, fetal bovine serum; DMEM, Dulbecco’s Modified Eagle’s Medium; SF, sorafenib.

Figure S3 UV spectra (A) and zeta potential (B) of the indicated formulations.

Abbreviations: Abs, absorbance; FA-GO, FA-conjugated GO; FA, folic acid; GO, graphene oxide; FA-GO/SF, FA-GO loaded with SF; SF, sorafenib; PVP, polyvinyl pyrrolidone; UV, ultraviolet.

Figure S4 Influence of GO, FA-GO, and FA-GO/SF on hemolysis.

Notes: Data are expressed as mean ± SD (n=3); *P<0.05, **P<0.01, as compared to GO.

Abbreviations: FA-GO, FA-conjugated GO; FA, folic acid; GO, graphene oxide; FA-GO/SF, FA-GO loaded with SF; SD, standard deviation; SF, sorafenib.

Figure S5 Flow cytometry results for (A) KB cells and (B) A549 cells exposed to FITC-loaded folic acid-conjugated graphene oxide.

Notes: Black line: control; red line: cells exposed to FITC-loaded FA-GO only; green line: cells pretreated with FA, followed by FITC-loaded FA-GO.

Abbreviations: FA-GO, FA-conjugated GO; FA, folic acid; GO, graphene oxide; FITC, fluorescein-5(6)-isothiocyanate.

Acknowledgments

This research was supported by the National Research Foundation of Korea (NRF) grant (2015R1A2A2A01004118, 2015R1A2A2A04004806) and the Medical Research Center Program (2015R1A5A2009124) funded by the Korea government (MSIP).

Disclosure

The authors report no conflicts of interest in this work.