Surface potential modulates fibronectin adsorption and molecular interaction on graphene-based materials.

Protein interactions on graphene-based materials (GBMs) are predominantly governed by interphase surface properties such as surface chemistry and roughness; however, the critical role of surface potential (SP) in modulating these interactions remains largely unexplored. In this work, we investigated a model study highlighting how two distinct GBMs [graphene oxide (GO) and reduced graphene oxide (RGO)] with different SP regulate protein interactions, spanning from macroscopic adsorption to molecular-level conformational changes. Through thermal reduction, hydrophilic GO was transformed into hydrophobic RGO, generating distinct SP of +120 mV for GO and +60 mV for RGO. This modulation in SP created a platform for differential protein interactions. The influence of SP on protein interactions was evident when fibronectin (FN) was introduced onto GO and RGO surfaces. Quartz crystal microbalance with dissipation and fluorescence microscopy revealed that the distinct SP of GO and RGO surfaces significantly affected FN adsorption. On the RGO substrate, which exhibited a lower SP, FN adsorption was ∼3 times greater than on the GO substrate. In contrast, FN on the GO adopted elongated fibrillar structures, driven by strong polar, hydrophilic, and electrostatic interactions at the molecular scale, regulating its conformation upon adsorption. Molecular docking simulations further supported these findings, indicating a stronger and more stable interaction between FN and RGO (binding energy C-score: -3.87, RMSD: 0.01 Å) than between FN and GO (C-score: -2.24, RMSD: 0.42 Å). Overall, this study underscores the pivotal role of SP of GBMs in modulating protein adsorption, binding stability, and conformational organization, providing key insights into the rational design of GBM biomaterials with tailored biointerface properties.