Improved pH-Controlled Release of Phenformin from Low-Defect Graphene Compared to Graphene Oxide

Graphene-based drug carriers provide a promising addition to current cancer drug 8 delivery options. Increased accessibility of high-quality graphene made by plasma- enhanced chemical vapor deposition (PE-CVD) makes it an attractive material to re-visit in comparison to the widely studied graphene oxide (GO) in drug delivery. Here we show the potential of re-purposing the metabolic drug phenformin for cancer treatment in terms of stability, binding, and pH-controlled release. Using covalent attachment of polyethylene glycol (PEG) onto pristine (PE-CVD) graphene, we show that the PEG stabilized graphene nanosheets (PGNS) drug carrier is stable in aqueous solutions, exhibit a higher binding affinity towards phenformin than conventional GO. Moreover, we experimentally demonstrate an improved drug release in PGNS than GO in pH levels lower than physiological conditions comparable to an acidic tumor microenvironment.