Folic-Acid-Functionalized Graphene Oxide Nanocarrier:\nSynthetic Approaches, Characterization, Drug Delivery Study, and Antitumor\nScreening

Abstract

In\nthis work, we developed and screened the potential antitumor\nactivity of a nanocarrier based on graphene oxide (GO) and folic acid\n(FA) for the delivery of chemotherapy drugs. GO was synthesized by\nthe graphite exfoliation process. FA was linked to PEG (4,7,10-trioxa-1,13-tridecanediamine)\nto form FA–PEG, followed by coupling to the GO surface. Camptothecin\n(CPT) was further adsorbed on GO for use as a drug model in the delivery\nstudy. The synthesis of the intermediate FA–PEG molecule and\ncoupling to GO for the formation of the GO–FA nanocarrier were\nconfirmed by basic and state-of-the-art characterization techniques,\nincluding infrared (FTIR) spectroscopy, thermogravimetric analysis\n(TGA), electrospray ionization (ESI) mass spectrometry, transmission\nelectron microscopy (TEM), and magic-angle spinning carbon-13 nuclear\nmagnetic resonance (CP/MAS ¹³C NMR) spectroscopy. FTIR\nspectroscopy showed a significant reduction in the signal intensity\nof the carboxylic groups after the functionalization of GO with FA–PEG.\nTGA of GO–FA revealed that approximately 20% of the functional\ngroups were from FA–PEG. GO–FA indicated a high CPT\nloading capacity (37.8%). <i>In vitro</i> studies confirmed\nprolonged drug release over 200 h. Acidic pH (5.0) slowed the release\nof CPT from the nanocarrier compared to that at physiological pH (7.4).\nThe toxicity screening of GO–FA and GO–FA + CPT was\ninvestigated for two widely studied preclinical cell models: J774,\na tumor cell with macrophage phenotype and high proliferation rate;\nand HepG2, a tumor cell obtained from human hepatocellular carcinoma\nwith folate transporters. The toxicity of the GO–FA nanocarrier\nwithout drug loading was dependent on the cell type and presented\nno toxicity to J774 but high toxicity to HepG2. The presence of FA\nin the nanocarrier loaded with CPT was crucial to achieve apoptosis\nin both tumor cell lines. In addition, confocal microscopy revealed\nboth the adhesion and internalization of the FITC-labeled GO–FA\nby the tumor cell lines.