We demonstrated that the individual graphene oxide sheets can be readily reduced under a mild condition using L-ascorbic acid ( L-AA). This simple approach should find practical applications in large scale production of water soluble graphene.

Herein, we report the effects of graphene oxides on human fibroblast cells and mice with the aim of investigating graphene oxides' biocompatibility. The graphene oxides were prepared by the modified Hummers method and characterized by high-resolution transmission electron microscope and atomic force microscopy. The human fibroblast cells were cultured with different doses of graphene oxides for day 1 to day 5. Thirty mice divided into three test groups (low, middle, high dose) and one control group were injected with 0.1, 0.25, and 0.4 mg graphene oxides, respectively, and were raised for 1 day, 7 days, and 30 days, respectively. Results showed that the water-soluble graphene oxides were successfully prepared; graphene oxides with dose less than 20 μg/mL did not exhibit toxicity to human fibroblast cells, and the dose of more than 50 μg/mL exhibits obvious cytotoxicity such as decreasing cell adhesion, inducing cell apoptosis, entering into lysosomes, mitochondrion, endoplasm, and cell nucleus. Graphene oxides under low dose (0.1 mg) and middle dose (0.25 mg) did not exhibit obvious toxicity to mice and under high dose (0.4 mg) exhibited chronic toxicity, such as 4/9 mice death and lung granuloma formation, mainly located in lung, liver, spleen, and kidney, almost could not be cleaned by kidney. In conclusion, graphene oxides exhibit dose-dependent toxicity to cells and animals, such as inducing cell apoptosis and lung granuloma formation, and cannot be cleaned by kidney. When graphene oxides are explored for in vivo applications in animal or human body, its biocompatibility must be considered.

Due to the high peroxidase-like activity and small lateral size of graphene quantum dots (GQDs), the covalently assembled GQDs/Au electrode exhibits great performance and stability in H₂O₂ detection. It is better or comparable to some enzyme-immobilized electrodes, and thus could be useful in sensing H₂O₂ changes in biological systems.

This review selectively describes the recent progress in the interactions of proteins (enzymes) and short-chain peptides with graphene and graphene oxide (GO). Particularly, the advances of the immobilization mechanisms of enzymes on graphene and GO, the catalytic properties of the immobilized enzymes, and their applications are summarized in detail. The interfacings of the peptides with graphene and GO, the as assembled conjugates, and their potential applications are discussed briefly. The possible ongoing development for the assembly of conjugates of graphene and GO with proteins and peptides in a controlled manner is speculated upon.