*DOI: http://dx.doi.org/10.5772/intechopen.103688 Advances in Graphene Platforms for Drug Delivery in Cancer and Its Biocompatibility*

The growth of solid tumors is characterized not only by the uncontrolled proliferation of cells but also by changes in the tumoral microenvironment. In solid tumors, hypoxic areas generally have a low pH. There may be low levels of glucose and other nutrients, as well as changes in temperature, all associated with various alterations in tumor cell metabolism [60]. While the heterogeneity of the tumor microenvironment sometimes makes it difficult to adequately characterize tumors [61], this has spawned interest in developing new nanotechnology therapeutic strategies to improve not only drug delivery conditions and directly destroy tumor cells, but also alter the balance between neoplastic cells and their microenvironment. Therefore, intelligent systems have been developed for the administration of drugs that respond to stimuli, and therapeutic agents can be activated by endogenous or exogenous stimuli [62, 63]. Platforms based on graphene have proven excellent due to their physicochemical properties since, according to the functional groups that are attached to them, they can be sensitive to changes in the tumor microenvironment or to intracellular signals in response to physical stimulus factors. Graphene platforms have been conjugated with functional chemical groups that allow the drug to be released when there are changes in pH and temperature [64]. For example, it has been observed that when pH-sensitive functional groups (COOH, ∙NH2, and SO3H) are added to graphene platforms, controlled drug release can be achieved in tumor areas [65]. The functionalization allows the pH of the platform to change in the bloodstream and, with this, remain in circulation for longer and favor the delivery and effectiveness of the treatment. This same effect has been achieved by changes in the loading of the platform. This was the case with the construction of the graphene platform with polymers such as polyethylene glycol and doxorubicin, where it was observed that the release of the drug is accelerated in an acidic environment [66]. Or with the construction of graphene microspheres conjugated with a dendrimer and maltose (Fe3O4@C@TDG) as a potential transporter to promote the release of doxorubicin and improve its therapeutic efficacy at specific pH [67]. Polymer aggregation has also served to make photoluminescence more stable at different pH for imaging tumor cells, which, as already mentioned, is part of the multifunctionality of the graphene platform.
