Decoupling Conductivity and Interfacial State in Pristine-Like Carbon Nanotube Coatings Reveals Their Distinct Contributions to Neuronal Function

Abstract Carbon nanotubes (CNTs) combine high electrical conductivity, mechanical robustness, and nanoscale architecture, making them promising materials for neural interfaces. However, the strong coupling between CNT morphology, electrical transport, and surface chemistry has limited identification of the material properties that directly regulate neuronal function. Here, we establish an experimental strategy to disentangle morphology-dependent network transport from interfacial wettability using pristine-like CNT coatings. Multiwalled CNTs with comparable diameters but distinct lengths were reversibly functionalized, spray-coated, and thermally defunctionalized to produce homogeneous conductive networks while recovering pristine-like electrical transport and surface chemistry. Subsequent conditioning in phosphate-buffered saline substantially reduced surface hydrophobicity without detectable alteration of the graphitic CNT framework, generating coatings with comparable interfacial wettability but distinct network morphologies. Primary spinal cord neuron-glia cultures grown on these substrates were characterized by immunocytochemistry, electrophysiology, and calcium imaging. All CNT coatings supported comparable neuroglial density and network formation, whereas PBS-conditioned coatings, characterized by a more wettable interface, consistently exhibited enhanced spontaneous bursting and calcium activity compared with their untreated coatings. Across all conditions, neuronal network activity was more consistently associated with the initial interfacial state of CNT coatings, as experimentally reflected by their wetting behavior, than with CNT length or morphology-dependent electrical transport. These findings identify the initial CNT interfacial state, with wettability serving as an experimentally accessible descriptor, as a key design parameter for CNT-based neural interfaces. Furthermore, they suggest that the initial interfacial state may influence the subsequent evolution of the biomolecular layer at the cell-facing interface, thereby contributing to the modulation of neuronal function.