Folic-Acid-Functionalized Graphene Oxide Nanocarrier: Synthetic Approaches, Characterization, Drug Delivery Study, and Antitumor Screening

In this work, we developed and screened the potential antitumor activity of a nanocarrier based on graphene oxide (GO) and folic acid (FA) for the delivery of chemotherapy drugs. GO was synthesized by the graphite exfoliation process. FA was linked to PEG (4,7,10-trioxa-1,13-tridecanediamine) to form FA–PEG, followed by coupling to the GO surface. Camptothecin (CPT) was further adsorbed on GO for use as a drug model in the delivery study. The synthesis of the intermediate FA–PEG molecule and coupling to GO for the formation of the GO–FA nanocarrier were confirmed by basic and state-of-the-art characterization techniques, including infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), electrospray ionization (ESI) mass spectrometry, transmission electron microscopy (TEM), and magic-angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy. FTIR spectroscopy showed a significant reduction in the signal intensity of the carboxylic groups after the functionalization of GO with FA–PEG. TGA of GO–FA revealed that approximately 20% of the functional groups were from FA–PEG. GO–FA indicated a high CPT loading capacity (37.8%). In vitro studies confirmed prolonged drug release over 200 h. Acidic pH (5.0) slowed the release of CPT from the nanocarrier compared to that at physiological pH (7.4). The toxicity screening of GO–FA and GO–FA + CPT was investigated for two widely studied preclinical cell models: J774, a tumor cell with macrophage phenotype and high proliferation rate; and HepG2, a tumor cell obtained from human hepatocellular carcinoma with folate transporters. The toxicity of the GO–FA nanocarrier without drug loading was dependent on the cell type and presented no toxicity to J774 but high toxicity to HepG2. The presence of FA in the nanocarrier loaded with CPT was crucial to achieve apoptosis in both tumor cell lines. In addition, confocal microscopy revealed both the adhesion and internalization of the FITC-labeled GO–FA by the tumor cell lines.