The objective of this research is to investigate the biocompatibility of carbon nanomaterial. It was found that the cytotoxicity of multiwalled carbon nanotubes (MWNTs) depend on their concentration, size, and surface chemical groups (e.g., -COOH). MWNTs and MWNT-COOH could accumulate in human lung macrophage cells (U937) to different degrees, and they did not produce overt cell toxicity within the concentration range of 5-50 µg/ml up to 24 h. However, there were morphological alterations at low doses of MWNT-COOH and significant reactive oxygen species (ROS) generation for MWNTs at higher doses, indicating a distinguished possible cellular stress response and DNA damage from both materials.
In the second part of this study, reduced graphene oxide (rGO) was demonstrated to show the concentration-dependent and cell-specific cytotoxicity. Specifically, rGO was found to stimulate cell proliferation of human skin fibroblast cells at relatively low concentrations (< 5 µg/mL), but inhibit human skin fibroblast cells proliferation at high concentrations. rGO-induced concentration-dependent and cell-specific generation of ROS and activation of NF-κB transcription factors were also observed, indicating an oxidative stress mechanism. Furthermore, rGO was showed to be more biocompatibility to human skin fibroblast cells with respect to mouse embryonic fibroblast cells (NIH-3T3 cells).
In the third part of this study, the soft lithography technique was used to build PDMS microfluidic devices for monitoring cells viability and performing dynamic study of the carbon nanomaterial biocompatibility. Compared to the traditional in vitro technique, this research opens up a new approach to biocompatibility evaluation of nanomaterials with a reduced usage of animal in toxicity study. By using the newly-developed microfluidic devices, the biocompatibility of MWNTs and rGO were investigated. It was found that both particles could enter into the circulation system in the microfluidic devices. Possible damage to bovine aortic endothelium cells (BAECs) caused by carbon nanomaterials was investigated. The interaction of MWNTs (1D) and rGO sheets (2D) with BAECs in both static (cell culture) and dynamic (microfluidic) environments indicated that both nanoparticles reduced the mitochondrial function and lipoprotein (LDL) uptake. These results were concentration and morphology depended. MWNTs showed a better biocompatibility than rGO in both static and dynamic environments, while the microfluidic tests exhibited better biocompatibilities than those in cell culture dishes for both nanoparticles.