**2. Materials and methods**

graphene oxide (rGO) instead of pristine graphene, because the oxidized forms are easier to process and can be dispersed in water while at the same time maintaining most of graphene's

Graphene oxide has shown great potential enhancing differentiation and proliferation of human stem cells in vitro, which tend to adhere to graphene plates. In particular, it favors differentiation of human neuronal stem cells (hNSC) toward neurons rather than glia cells [2]. Combined with its inherent flexibility and strength, the possibility of creating a 3D structure that mimics the original organ, graphene appears to be a great scaffold for stem cell-based

Furthermore, a lot of research has come forward regarding the use of graphene in biosensors. Compared to previously used materials, graphene shows increased resistance and sensitivity. Also, being biocompatible it can be worn, allowing for the possibility of a permanently used sensor. Additionally, graphene can be bound to a wide range of molecules and proteins that

Another field to which graphene's ability to be bound to specific molecules has been applied is drug carrying and delivery. In particular, it has been successfully used for specific anticancer drug delivery [5]. It presents novel perspective in combining site detection and drug delivery. Peptides bound to the GO plates allow for detection by specific cell types, minimiz-

Graphene's use in the medical field raises a lot of questions regarding its safety and toxicity. In this regard, there are many conflicting studies and opinions. It appears that the matter of toxicity varies greatly depending on the physicochemical characteristics of the administrated graphene, also on the form of administration, and the model, varying between different species and cell types. The characteristics of graphene like concentration, dimensions (lateral and number of layers), surface structure functional groups, and protein corona influence its toxicity in biological systems. Despite its relevance to the effect, some toxicological studies do not give a proper characterization of the form of graphene used. Though most agree on the interaction of graphene with the cellular membrane, the question of its uptake is more controversial [7]. For example, the studies of Yue et al. on the viability of six different cell lines when treated with GO of varying dimensions show that only two phagocytic cell lines were able to internalize both nano- and micro-sized GO sheets. Furthermore, there was no difference in the viability of any of the six cell line studies when the concentration was lower than 20 μg/mL. On the other hand, inhalation of GO particles may lead to an accumulation in the

Interestingly, although GO does not show to be absorbed through the gastrointestinal tract, a low dose of GO can cause more damage to the gastrointestinal surface being drank as a suspension than a high dose of GO [9]. Most toxic effects seem to surge from the use of high doses of GO and the sequential aggregation and formation of conglomerates than can block small blood vessels and result in dyspnea [10]. However, recent publications detect no pathological effects in mice exposed to low dosages of GO and functionalized graphene when adminis-

properties.

84 Scientometrics

therapy [3].

allow for better selectivity [4].

ing uptake by other healthy cells [6].

trated by intravenous injection [11].

pulmonary surfactant and initiate an inflammatory process [8].
