Periodic Reporting for period 4 - SmartCardiacPatch (Next-Generation Cardiac Tissue Engineering: Smart Self-Regulating Patches)
Reporting period: 2020-01-01 to 2021-06-30
Ischemic heart disease (IHD) is the most common cause of death in the Western world, accounting for more than 1.8 million deaths each year in Europe, with an annual costs in excess of € 60 billion in the European Union alone. Myocardial infarction (MI) results from blockage of one of the coronary arteries that supply the cardiac tissue, leading to ischemia of a segment of the heart. This process eventually leads to the death of contractile cells and the formation of scar tissue. Since cardiomyocytes cannot proliferate, and the number of stem cells in the heart is limited, the cardiac tissue is unable to regenerate, leading to chronic cardiac dysfunction. Complications following an initial MI include heart failure, recurrent ischemia, and arrhythmias; jointly, they manifest a five-year mortality rate of near 50%. Currently, the only cure for the end-stage heart failure is cardiac transplantation. As cardiac donors are scarce, there is an urgent need to develop new strategies that will promote heart regeneration and thereby limit morbidity and mortality from this disease. Cardiac tissue engineering has evolved as an interdisciplinary field of technology combining principles from the material, engineering and life sciences with the goal of developing functional substitutes for the injured myocardium. Rather than simply introducing cells into the diseased area to repopulate the injured heart and restore function, cardiac tissue engineering involves the seeding of contracting cells in or onto 3-dimensional (3D) scaffolds prior to transplantation. Following implantation and full integration in the host, the scaffold degrades, leaving a functional cardiac patch on the defected organ. However, once the 3D cardiac patches have been engineered, the assessment of their quality in terms of electrical activity, without affecting their performance, is limited. This situation might lead to implantation of cardiac patches with limited or no potential to regenerate the infarcted heart. More importantly, the ability to monitor the performance of these patches and control their function following implantation is completely lost. The objective of this project is to expand far beyond the state-of-the-art by developing a conceptually new approach to engineer the next generation of smart cardiac patches. These patches will integrate complex electronics with engineered cardiac tissues to enable complete on-line monitoring and self-regulation of the tissue function, from the initial stage of the engineering process and through attainment of the full regeneration of the heart in the living body.
In this research, we designed and generated electrode-incorporating patches for cardiac tissue engineering that enable recording of extracellular potentials, provision of electrical stimulation and on-demand release of biomolecules. We proved the in-vitro performance of these patches, with on-going experiments being made to assess their performance in the context of a living body. Specifically, we used photolithography to generate novel, free-standing multielectrode microelectronic chips with gold electrodes designated for recording/stimulation or control release of active biomolecules. A special design made these electrodes flexible and stretchable so that they can withstand the dynamic environment of the beating heart. For incorporation of on-demand controlled release systems, electroactive polymers loaded with bioactive molecules were deposited on designated pads. The microelectronic chips are then integrated within cardiac-cells containing 3D ECM-like scaffolds made of electrospun polycaprolactone-gelatin fibers to compose the microelectronic cardiac patches (microECP) . A second type of devices was designed using electrospun biodegradable albumin fiber scaffolds patterned with gold electrodes. Cardiomyocytes incorporated within the patches found to be elongated, with a high aspect ratio and massive striation, providing indication on the maturation of the cells and formation of tissue with hallmarks of the native myocardium. We also developed a unique formulation of autologous, thermoresponsive ECM-based hydrogels, originated from decellularized omental tissue. Experiments are now being conducted to test their capacity to function as the biomaterial component of the microECP. In addition, we established a method in which a multi-nozzle 3D printer is being used to simultaneously deposit electronics together with ECM hydrogel and cardiac cells. The ability of the hybrid patches to detect electrical signals produced by cardiomyocytes was successfully demonstrated. The microECP as well as the albumin device and the 3D-printed electrode-containing patches recorded spikes that were regularly spaced and exhibited a shape and width consistent with cardiomyocyte extracellular signals. Moreover, we demonstrated the capacity of these constructs to control and interfere with the patch function by applying electrical stimulation at different frequencies. The ability to remotely release bioactive drugs and factors on demand through the built-in electronics has also been demonstrated. Experiments are now being performed to assess the capability of cardiac patches to survive and perform in the context of a living animal. preliminary assays showed high cell viability and structural integrity of electrode-free scaffolds. We also got Indications on an improvement in cardiac functionality upon implantation on infarcted hearts. These results indicate on the functionality of the biological component of the system. Future experiments, which design will soon be finalized, will provide essential information also on the in-vivo performance of the integrated electronics.
The patches enable the recording of cellular electrical activities and provide, for the first time, on-demand, remote interference to regulate tissue performance by provision of electrical stimulation and by releasing of drugs in the patch microenvironment. Future work will focus on the assessment of the potential of the smart cardiac patches to perform in the contexts of the living body and to improve the function of infarcted animal’s hearts.