Graphene Oxide and Pluronic Copolymer Aggregates–Possible Route to Modulate the Adsorption of Fluorophores and Imaging of Live Cells

In recent years, amphiphilic triblock copolymers have attracted increasing attention due to their tunable properties and biocompatible nature, and the degree of hydrophobicity of these block copolymers can be modulated by varying the hydrophobic poly­(propylene oxide) (PPO) blocks and hydrophilic poly­(ethylene oxide) (PEO) moieties. Beside these, compared to the conventional micelles, block copolymer aggregates are more heterogeneous. For this reason, we have chosen two different fluorophores with different hydrophobicity so that we can monitor the different regions into the aggregates. We have shown the effect of theses Pluronic block copolymer aggregates on the adsorption of two fluorophores on the graphene oxide (GO) surface. The PPO segment of the block copolymer strongly interact with the hydrophobic basal plane of GO. Thus, in the presence of these aggregates the interaction between the GO and fluorophores is restricted depending on their location into the aggregates. The adsorption of the fluorophores is also dependent on the hydrophobicity of the aggregates. In most of the cases, the adsorption phenomena follow the traditional Langmuir isotherm. Further, fluorescence correlation spectroscopy (FCS) study successfully provides insight into the molecular diffusion of these fluorophores adsorbed on GO surface. In water, almost equal amount of fluorophores are adsorbed irrespective of their nature. However, in pluronic aggregates, the amount of adsorbed fluorophores decreases significantly depending on their position and hydrophobicity. In addition, our FCS result indicates that the molecular diffusion of these fluorophores in the presence of GO and triblock copolymer deviate from the normal Fickian diffusion and show anomalous superdiffusion. Finally, we have also demonstrated that fluorophore loaded block copolymer and GO can be used as an effective tool for the live cell imaging. In the presence of pluronic aggregates, fluorophores can be distributed in most of the cell surface, and cellular uptake of GO is also increased. Furthermore, due to the biocompatible nature of these pluronics, GO-P123 can serve as a drug delivery vehicle.