Bioinspired Flexible Helical Electrospun Mat for Cardiac Patch Application

<b>Overview</b>: Fiber orientation dictates mechanical properties such as mechanical flexibility and porosity. Controlling these properties allows for increased and improved growth of cardiomyocytes for cardiac patch applications. Our work focused on developing helically coiled fiber mats made of polycaprolactone produced via electrospinning, then testing the biocompatibility and function of these fibers in a cardiac patch application and comparing these results to patches reinforced with aligned fibers and patches without fibers.<br/><b>Background:</b> Helically coiled structures are found in nature from animal to the plant world and provide mechanical support, higher porosity, and increased flexibility. Replicating these structures via electrospinning as a manufacturing method, helically coiled nanofibers promote elasticity and flexibility and have a large surface area for biomolecular interactions, which is suitable for cardiovascular applications due to the demanding dynamic environment of cardiovascular tissue.<br/><b>Methods and Results:</b> Two types of polycaprolactone fibers were produced via electrospinning; aligned fibers and helically coiled fibers. Fiber formation was dictated by the electrospinning parameters, specifically the flow rate of the polymer solution through the syringe. The biocompatibility and function of these fiber scaffolds were tested by encasing the fiber scaffolds in a hydrogel comprised of gelatin glycidyl methacrylate. Fibronectin was added to this hydrogel to increase biocompatibility and aid in cardiomyocyte attachment and spreading. This hydrogel was seeded with cardiomyocytes differentiated from human-induced pluripotent stem cells to form a preliminary cardiac patch. In total three types of patches were produced: a cardiac patch containing aligned fibers, a cardiac patch containing helically coiled fibers and a third cardiac patch containing no fibers. The cardiac patches were then placed on a holder made of PDMS that provided a passive mechanical stimulus to the cardiomyocytes. These holders were placed in a 12-well plate, and the cardiomyocytes seeded in the cardiac patch scaffold were incubated for 28 days. Cell media was regularly changed to provide the cells with nutrients. Cell growth, cell viability, and cardiomyocyte function were monitored and compared within the three patches. Additionally, the cardiac patch mechanics were examined using nanoindentation, tensile testing, and Raman spectroscopy to discuss the overall suitability of the fibrous mat in cardiac tissue engineering applications.