Cell-cell communication plays a pivotal role in coordination and function of biological systems. Three-dimensional (3D) spheroids provide venues to explore cellular communication for tissue development and drug discovery, as their 3D architecture mimics native in vivo microenvironments. Cellular electrophysiology is a prevalent signaling paradigm for studying electroactive cells. Currently, electrophysiological studies do not provide direct, multisite, simultaneous investigation of tissues in 3D. In this study, 3D self-rolled biosensor arrays (3D-SR-BAs) of either active field-effect transistors or passive microelectrodes were implemented to interface human cardiac spheroids in 3D. The arrays provided continuous and stable multiplexed recordings of field potentials with high sensitivity and spatiotemporal resolution, supported with simultaneous calcium imaging. Our approach enables electrophysiological investigation and monitoring of the complex signal transduction in 3D cellular assemblies toward an organ-on-an-electronic-chip (organ-on-e-chip) platform for tissue maturation investigations and development of drugs for disease treatment, such as arrhythmias.

Smart bioelectronics fabricated from nanocarbons have the potential to enable seamless integration with electrogenic cells and tissues.

The role that mechanical forces play in shaping the structure and function of the heart is critical to understanding heart formation and the etiology of disease but is challenging to study in patients. Engineered heart tissues (EHTs) incorporating human induced pluripotent stem cell (hiPSC)–derived cardiomyocytes have the potential to provide insight into these adaptive and maladaptive changes. However, most EHT systems cannot model both preload (stretch during chamber filling) and afterload (pressure the heart must work against to eject blood). Here, we have developed a new dynamic EHT (dyn-EHT) model that enables us to tune preload and have unconstrained contractile shortening of >10%. To do this, three-dimensional (3D) EHTs were integrated with an elastic polydimethylsiloxane strip providing mechanical preload and afterload in addition to enabling contractile force measurements based on strip bending. Our results demonstrated that dynamic loading improves the function of wild-type EHTs on the basis of the magnitude of the applied force, leading to improved alignment, conduction velocity, and contractility. For disease modeling, we used hiPSC-derived cardiomyocytes from a patient with arrhythmogenic cardiomyopathy due to mutations in the desmoplakin gene. We demonstrated that manifestation of this desmosome-linked disease state required dyn-EHT conditioning and that it could not be induced using 2D or standard 3D EHT approaches. Thus, a dynamic loading strategy is necessary to provoke the disease phenotype of diastolic lengthening, reduction of desmosome counts, and reduced contractility, which are related to primary end points of clinical disease, such as chamber thinning and reduced cardiac output.

Three-dimensional (3D) neuronal spheroid culture serves as a powerful model system for the investigation of neurological disorders and drug discovery. The success of such a model system requires techniques that enable high-resolution functional readout across the entire spheroid.Conventional microelectrode arrays and implantable neural probes cannot monitor the electrophysiology activity across the entire native 3D geometry of the cellular construct. Here, we demonstrate a 3D self-rolled biosensor array (3D-SR-BA) integrated with a 3D cortical spheroid culture for simultaneous in-vitro electrophysiology recording, functional Ca 2+ imaging, and drug effect monitoring. We have also developed a signal processing pipeline to detect neural firings with high spatiotemporal resolution from the electrophysiology recordings based on established spike sorting methods. The 3D-SR-BAs cortical spheroid interface provides a stable, high sensitivity recording of neural action potentials (< 50 µV peak-to-peak amplitude). The 3D-SR-BA is demonstrated as a potential drug screening platform through the investigation of the neural response to the excitatory neurotransmitter glutamate. Upon addition of glutamate, the neuronal firing rates increased notably corresponding well with the functional Ca 2+ imaging. Our entire system, including the 3D-SR-BA integrated with neural spheroid culture, enables simultaneous electrophysiology recording and functional Ca 2+ imaging with high spatiotemporal resolution in conjunction with chemical stimulation. We demonstrate a powerful toolset for future studies of tissue development, disease progression, and drug testing and screening, especially when combined with native spheroid cultures directly extracted from humans.

The role mechanical forces play in shaping the structure and function of the heart is critical to understanding heart formation and the etiology of disease but is challenging to study in patients. Engineered heart tissues (EHTs) incorporating human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes have the potential to provide insight into these adaptive and maladaptive changes in the heart. However, most EHT systems are unable to model both preload (stretch during chamber filling) and afterload (pressure the heart must work against to eject blood). Here, we have developed a new dynamic EHT (dyn-EHT) model that enables us to tune preload and have unconstrained fractional shortening of >10%.To do this, 3D EHTs are integrated with an elastic polydimethylsiloxane (PDMS) strip that provides mechanical pre-and afterload to the tissue in addition to enabling contractile force measurements based on strip bending. Our results demonstrate in wild-type EHTs that dynamic loading is beneficial based on the magnitude of the forces, leading to improved alignment, conduction velocity, and contractility. For disease modeling, we use hiPSC-derived cardiomyocytes from a patient with arrhythmogenic cardiomyopathy (ACM) due to mutations in desmoplakin. We demonstrate that manifestation of this desmosome-linked disease state requires the dyn-EHT conditioning and that it cannot be induced using 2D or standard 3D EHT approaches. Thus, dynamic loading strategy is necessary to provoke a disease phenotype (diastolic lengthening, reduction of desmosome counts, and reduced contractility), which are akin to primary endpoints of clinical disease, such as chamber thinning and reduced cardiac output.Studying the effects of mechanical loading on adaptive and maladaptive changes in heart structure and function is challenging in human patients, driving the need to develop new approaches. Animals have been used to model a wide range of human cardiovascular disease states, but there are inherent differences in physiology, gene expression and pharmacokinetics that limit the ability to replicate complex pathology (6). In vitro 2-dimensional (2D) culture of cardiomyocytes on microengineered surfaces have been used to study structure-function relationships and to create region-specific ventricular myocardium (7,8) Muscular thin films (MTFs), consisting of cells cultured on a flexible film, have enabled these 2D platforms to measure contractility (9,10), and combined with patient-specific human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes can model cardiomyopathies such as Barth's syndrome (11). However, 2D cardiomyocytes are adhered to a surface (12) and thus do not have the same mechanical cell-cell coupling as found in the native heart (13). To address this, researchers have developed more physiologically-relevant 3D engineered heart tissues (EHTs) in the form papillary muscle-like linear bundles (14-18) myocardium-like sheets (19,20), and ventricle-like chambers (21,22). Incorporating human induced pluripotent stem cell (hi...