Graphene has drawn a lot of interest in the material community due to unique physicochemical properties. Owing to a high surface area to volume ratio and free oxygen groups, the oxidized derivative, graphene oxide (GO) has promising potential as a drug delivery system. Here, the lung tolerability of two distinct GO varying in lateral dimensions is investigated, to reveal the most suitable candidate platform for pulmonary drug delivery. Following repeated chronic pulmonary exposure of mice to GO sheet suspensions, the innate and adaptive immune responses are studied. An acute and transient influx of neutrophils and eosinophils in the alveolar space, together with the replacement of alveolar macrophages by interstitial ones and a significant activation toward anti-inflammatory subsets, are found for both GO materials. Micrometric GO give rise to persistent multinucleated macrophages and granulomas. However, neither adaptive immune response nor lung tissue remodeling are induced after exposure to micrometric GO. Concurrently, milder effects and faster tissue recovery, both associated to a faster clearance from the respiratory tract, are found for nanometric GO, suggesting a greater lung tolerability. Taken together, these results highlight the importance of dimensions in the design of biocompatible 2D materials for pulmonary drug delivery system.

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.

BackgroundGraphene oxide (GO) is a highly oxidized graphene form with oxygen functional groups on its surface. GO is an excellent platform to support and stabilize silver nanoparticles (AgNP), which gives rise to the graphene oxide-silver nanoparticle (GOAg) nanocomposite. Understanding how this nanocomposite interacts with cells is a toxicological challenge of great importance for future biomedical applications, and macrophage cells can provide information concerning the biocompatibility of these nanomaterials. The cytotoxicity of the GOAg nanocomposite, pristine GO, and pristine AgNP was compared toward two representative murine macrophages: a tumoral lineage (J774) and peritoneal macrophages collected from Balb/c mouse. The production of reactive oxygen species (ROS) by J774 macrophages was also monitored. We investigated the internalization of nanomaterials by transmission electron microscopy (TEM). The quantification of internalized silver was carried out by inductively coupled plasma mass spectrometry (ICP-MS). Nanomaterial stability in the cell media was investigated overtime by visual observation, inductively coupled plasma optical emission spectrometry (ICP OES), and dynamic light scattering (DLS).ResultsThe GOAg nanocomposite was more toxic than pristine GO and pristine AgNP for both macrophages, and it significantly induced more ROS production compared to pristine AgNP. TEM analysis showed that GOAg was internalized by tumoral J774 macrophages. However, macrophages internalized approximately 60 % less GOAg than did pristine AgNP. The images also showed the degradation of nanocomposite inside cells.ConclusionsAlthough the GOAg nanocomposite was less internalized by the macrophage cells, it was more toxic than the pristine counterparts and induced remarkable oxidative stress. Our findings strongly reveal a synergistic toxicity effect of the GOAg nanocomposite. The toxicity and fate of nanocomposites in cells are some of the major concerns in the development of novel biocompatible materials and must be carefully evaluated.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-016-0165-1) contains supplementary material, which is available to authorized users.