PHOTOTHERAPEUTIC FUNCTIONALITY OF BIOCOMPATIBLE GRAPHENE OXIDE/ DENDRIMER HYBRIDS
National Taiwan University of Science and Technology, Taiwan
Graphene oxide (GO) is an oxidized graphene chemically functionalized with oxygen-including groups such as hydroxyl, carboxylic acid and epoxide. Hybrid materials of GO have been investigated as new promising materials for biomedical applications including cellular imaging, drug delivery, and photodynamic therapy. Poly(amido amine) (PAMAM) dendrimers, highly-branched polymers with a multifunctionalized peripheral surface, have high degree of molecular uniformity, monomolecular weight, and specified size and shape. PAMAM dendrimers also possess a strong fluorescence emission. It has been confirmed by the visual observation of fluorescent dendrimers that fluorescent dendrimers-bound avidins interact selectively with biotins immobilized on the patterned substrates. The fluorescent PAMAM dendrimers have revealed lower in vitro cytotoxicity than the non-fluorescent ones toward rat C6 glioma cells.
In this study, hydroxyl-terminated fourth generation PAMAM dendrimer and folic acid were chemically bound on graphene oxide. The resultant hybrids exhibited one-photon and two-photon fluorescence emission, since the excitation irradiation at 390 and 780 nm on the hybrids brought a fluorescence emission in the visible region around 450 nm. In addition, the photocytotoxicity study revealed that under the two-photon excitation at 780 nm, the hybrids can absorb near-infrared light and generate reactive oxygen species which can oxidize the HeLa cells and cause their death, suggesting the phototherapeutic behavior. Cytotoxicity measurement revealed the high biocompatibility of the hybrids toward HeLa cells. Thus, the present biocompatible hybrids consisting of only dendrimer, folic acid and graphene oxide have potentials as photodynamic therapeutic agents for medical treatment.