The novel and fascinating properties of graphene-based materials suggest that these materials may have many potential biomedical applications . Graphene oxides are a class of nano-materials in the size range of 1-100 nm and fall into a category of two-dimensional carbonaceous nanomaterials with dimensions of approximately a few nanometers in thickness. Owing to the unique physio-chemical properties of graphene oxide (GO), including the available surface oxygen groups, GO can form a stable suspension in different solvents, indicating its hydrophilic nature within the family of carbonaceous nanomaterials . Due to the presence of a unique surface to volume ratio, along with surface properties such as a huge concentration of surface atoms, augmented surface energy value, and other characteristics, makes GO a suitable candidate for a myriad of applications. Potential applications range from biomedical applications (viz. drug delivery, protein therapy etc.) and bioengineering (biosensors and bioimaging) to anti-microbial therapy and bioengineering (scaffolding of tissue) [3, 4]. Due to its high surface to volume ratio, GO sheets provide a reactivity and adsorption platform for other biological macromolecules enabling bioprocesses to occur at a nanoscale level that are mesoscopic in nature . The probability of redox reactions between the material and a biological system due to the free electrons present on the surface of graphene oxide sheets, increases the number of potential applications of carbonaceous nano-materials in biological systems .
Nanobiotechnology has emerged as a promising platform for employing nanomaterials in the field of cancer biology . Due to the unique physio-chemical properties of the nanomaterials, the same could be used for targeted drug delivery for bearing the outcompeting behavior of natural delivery mechanisms such as reaching the nuclear membrane and penetrating it for delivery in the proteins and the DNA sequences . Graphene oxide [GO] has been recently proposed as a good agent in cancer therapeutics and diagnosis . The morphology and the viability of the glioma cells U87 and U118 respectively, have been shown to be less effective from the treatment of GO sheets . Also, Chang et al.,  has studied the adverse effect over the A549 cells due to the generation of oxidative stress by GO. It has also been reported that GO sheets bring significant damage to the mitochondrial membrane, resulting in altered mitochondrial potential . Compared to other nano-scaled nanomaterials, such as gold and silver nanoparticles which are used in different medical therapies, carbonaceous materials like GO have lesser deleterious intrinsic activity in the drug delivery process of DNA, RNA for achieving targeted drug delivery mechanism [11, 12]. The great convenience of using graphene oxide [GO] over other carbon-based materials is due to its aqueous dispersibility and colloidal stability in both single or few-layered GO. As a result, these materials are becoming immensely popular as novel tools in the biomedical field.
The surface properties of pristine graphene oxide and graphene sheets increases their overall potential for activity within biocompatible applications . In this regard, an interaction between GO sheets and targeted ligands in lung epithelial cells , neuronal cells  and fibroblast cells has been reported [Gao et al, 2012]. Furthermore, the use of GO sheets in conjunction with sulfonic acid in drug delivery systems makes the GO suspension more stable, while decorating the sheets with folic acid molecules has been used to target human breast cancer cells with folic acid receptors . Folic acid-conjugated GO sheets have been employed for the delivery of anti-cancer drugs, such as doxorubicin and calprotectin, into tumor cell lines with great success in MGC803 cells . Yang et al., 2010 reported that a higher rate of uptake in tumor cells and in-vivo photothermal therapy was achieved by using PEGylated Graphene sheets in a mouse model subjected to an ultra-low power laser injection of 2Wcm− 2. The interaction of graphene with DNA/RNA macromolecules favors the use of GO sheets over GO alone, due to the presence of the carboxylic, hydroxide, and epoxy groups present in GO sheets, which provides greater potential bioactivity and thus, greater potential application in a wide range of biomedical fields and bio-macromolecular systems . The higher rate of drug adsorption to hydrophobic materials also makes GO a preferred choice amongst the graphene family of nano-scaled materials, such as graphene, rGO (large GO), and others . Extensive studies of graphene-based materials for different biomedical applications have fostered nano-biomaterial development for practical use and commercialization.More studies on graphene are required, however, to achieve safe and effective commercial applications of this technology.
In this present study, the Hummers method, with some modifications, such as the use of sulphuric acid [H2SO4], and varying the Graphite: KMn04 ratio in the reaction mixture, was used to optimize GO production. The cytotoxic activity of the GO nanosheets against the MDA-MB-231 breast cancer cell line was also evaluated, along with its effect on a normal, HaCaT cell line. During the application of any foreign biomaterials, there is the potential of inducing oxidative stress. Therefore, the DDPH radical and peroxide scavenging assays were also conducted. Results of the study indicate that oxidation plays a key role in the activity of GO nanosheets in biological systems.