Abstract
Cardiovascular diseases (CVDs) are the top global cause of death, causing ~31% of all deaths annually. Despite CVDs' burden on healthcare services, from 1990 to 2012 there was a decline in the research into CVDs. While research is starting to increase again, basic research – interrogating the mechanisms behind CVDs – has shown the least growth. Part of the reason for this turbulent trend in research is that cardiac cell types are challenging to culture ex vivo. Carbon nanotubes (CNTs), combined with tissue engineering techniques, are uniquely suited to providing dynamic new experimental platforms for CVD research due to their versatility in biomaterial formulations, structural similarity to cardiac extracellular proteins and, principally, their electrical conductivity. Systematic review of literature identified conventions in CNT-based tissue scaffolds and engineering, a paucity of research applying physiological electrical stimulation, the optimal stimulation protocol for human cardiac tissue culture, and gaps in the research that this project may help to fill. In the present project, electrically conductive tissue scaffolds, composed of multi-walled, carboxyl functionalised (MWCOOH) CNTs, were created for human iPSC-derived cardiomyocytes, as a platform for cardiac disease modelling and pharmaceutical research. These thin, isotropic networks of CNTs were transparent, had kΩ range resistivity, nanoscale surface topography, and hydrophilic properties translating to biocompatibility. CMs on CNTs showed significantly enhanced beat frequency and, using the same materials, prototype devices for electrical stimulation of CMs were also created for pacing of CM contractions. Immunofluorescence of cardiac specific α-actin and the focal adhesion protein talin showed phenotypic maintenance and strong adherence to CNT scaffolds, respectively. Investigations into CM’s enhanced beat frequency via gene expression of Ca2+ handling proteins exposed dysfunction in intracellular Ca2+ storage and release due to significant under expression of calsequestrin-2, FKBP12, SERCA2a, Ncx1.1 and Cx43. To our knowledge, this is the first such investigation into the sole effects of CNTs on in vitro CM calcium handling protein expression and may have led to a potentially clinically relevant form of arrhythmia, without needing the use of electrical pacing stimulation. By virtue of materials science innovations alone, this project has made strides towards creating a marketable platform for disease modelling in cardiac pharmaceutical research with a view to reinvigorate the search for novel cardiac therapies.