In vitro cytotoxicity evaluation of graphene oxide from the peroxidase-like activity perspective

In this study, PEGylated graphene oxide (PEG-GO)-hemin composite structure was constructed. Hemin in the form of nanoscaled aggregates were immobilized on PEG-GO sheets by the pi-pi stacking super molecular interaction. Via catalyzing the oxidation of chromogenic substrates, we elicited the obtained PEG-GO-Hemin composite sheets have much higher peroxidase-like activity compared to hemin or PEG GO alone, which is due to the introduction of enzyme active center of hemin with high dispersity, the excellent affinity to organic substrate through pi-pi stacking and/or electrostatic adsorption and the rapid electron transfer capability of PEG-GO. Similarly, PEG-GO-Hemin was found to be able to catalyze the oxidation of low density lipoprotein (LDL) by H2O2, resulting in toxicity to porcine iliac endothelial cells (PIECs) in vitro. Furthermore, we also demonstrated that PEG-GO sheets showed enhanced peroxidase activity when met hemin containing proteins including hemoglobin and cytochrome c. High glucose level (HG) in human umbilical vein endothelial cells (HUVECs) can induce cytochrome c to release from the respiratory chain, thus applying PEG-GO under HG condition could cause a much higher peroxidase-like activity, resulting in the production of hydroxyl radical (center dot OH) and cytochrome c radical (cytochrome c center dot), which eventually enhance the apoptosis. These results suggest GO has potential hazard for biomedical applications in some pathophysiological conditions. (C) 2016 Elsevier B.V. All rights reserved.