Photoresponsive Dispersion and Acutation of Graphene-Elastin Hybrid Materials

In the field of bioengineering, graphene-derivatives (GDs) have emerged as promising nanomaterials for incoporation into sensors, therapeutics, and biomaterials due to their mechanical strength, thermal/electrical conductivity, optical properties, and low cost. However, as a consequence of their poor colloidal stability and lack of inherent specificity towards specific targets, GDs generally require covalent or non-covalent modifications before they can function in biological systems.  Here we describe the one-step non-covalent functionalization of GDs, i.e. graphene oxide (GO), and reduced graphene oxide (rGO) with a genetically engineered, protein-based polymer. Specifically, we utilzed elastin-like polypeptides (ELPs) due to their tunable thermoresponsiveness (reversible aggregation above a critical temperature), biocompatibility, and mechanical properties. ELPs genetically engineered to display a phage-display derived graphene-binding petpide motif  were shown to bind to both GO and rGO and stabilize their dipersion in aqueous and organic solvents. The ELP-GD hybrids retained a stimuli-responsive behavior both in solution, and when incorporated into hydrogels resulting in reversible aggregation/dispersion and swelling/deswelling, respectively.  Furthermore, these responses could be induced remotely by infrared light illumination as a result of the GDs' ability to convert IR to heat. In the case of hydrogels, local IR stimulation allowed for controlled actuation due to non-uniform deswelling. Finally, we demonstrated that further engineering of ELP-GDs with integrin-binding motifs allows for efficient cell adhesion onto GD surfaces. GD functionalization with genetically engineered ELPs provides a facile and tunable method for imparting multiple functions and stimuli-responsiveness. This strategy can be utilized in the future for theranostics, sensing, and tissue engineering, as well as be adapted for use with other nanoparticles.