Carbon nanotubes (CNTs) have generated substantial research interests since their discovery in 1991. Individual CNTs possess exceptional mechanical (1000x strength of steel), electrical (almost 2x electrical conductivity of copper), and thermal (almost 2x thermal conductivity of diamond) properties, all at a fraction of the weight. As a result of these outstanding properties, CNTs are ideal candidates in applications such as sensors, energy storage and conversion, batteries, touch screen displays, field emitters, super capacitors, aerospace, wearables, biosensors, nanomedicine, and novel biomaterials. Early CNT applications use CNTs as individual molecules, coatings, or part of composites. With advancements in CNT processing, researchers have been able to fabricate CNTs into macroscopic 1D, 2D, and 3D objects with outstanding properties, such as CNT fibers (CNTFs), films, and foams. This thesis focuses on the biomedical applications of two such CNT macrostructures – CNTFs and CNT films.

First, this thesis demonstrates in vivo restoration of myocardial conduction with CNTFs. Impaired myocardial conduction is the underlying mechanism for re-entrant arrhythmias. A restorative therapy had remained elusive due to the lack of biocompatible materials that restore myocardial conduction. CNTFs are uniquely suited to fill this need because they combine the mechanical properties of soft sutures with the conductive properties of metals. Here, by showing that CNTFs sewn across the mitral valve can create or restore conduction across anatomical barriers, we demonstrate CNTF to be a potential long-term restorative solution in pathologies interrupting efficient myocardial conduction.

It is important to understand a material’s bio- and immune-compatibility profiles before it can be safely used as implanted bioelectronic interfaces. Therefore, the next part of this thesis systematically evaluates CNTF’s cellular, hematologic, immunologic, and organ compatibilities. Studies here show that 1) CNTF is biocompatible for both in vitro basic research and in vivo biomedical applications; 2) CNT macrostructures such as CNTF do not belong to the previously established “fiber pathogenicity paradigm” for CNTs. These results also establish baseline biocompatibility requirements for any future CNT-macrostructure-based bioelectronic interfaces.

Finally, this thesis presents flexible and transparent neural electrode arrays made from CNT films for integrated optical and electrical investigations. These CNT electrodes are transparent, flexible, and possess low interface impedance. Their capacity to carry out integrated optical and electrical investigations is demonstrated through electrophysiological recording during concurrent calcium imaging in hydra.