Multi-Imaging Method to Assay the Contractile Mechanical Output of Micropatterned Human iPSC-Derived Cardiac Myocytes.

RATIONALE: During each beat, cardiac myocytes (CMs) generate the mechanical output necessary for heart function through contractile mechanisms that involve shortening of sarcomeres along myofibrils. Human-induced pluripotent stem cells (hiPSCs) can be differentiated into CMs (hiPSC-CMs) that model cardiac contractile mechanical output more robustly when micropatterned into physiological shapes. Quantifying the mechanical output of these cells enables us to assay cardiac activity in a dish. OBJECTIVE: We sought to develop a computational platform that integrates analytic approaches to quantify the mechanical output of single micropatterned hiPSC-CMs from microscopy videos. METHODS AND RESULTS: We micropatterned single hiPSC-CMs on deformable polyacrylamide substrates containing fluorescent microbeads. We acquired videos of single beating cells, of microbead displacement during contractions, and of fluorescently labeled myofibrils. These videos were independently analyzed to obtain parameters that capture the mechanical output of the imaged single cells. We also developed novel methods to quantify sarcomere length from videos of moving myofibrils and to analyze loss of synchronicity of beating in cells with contractile defects. We tested this computational platform by detecting variations in mechanical output induced by drugs and in cells expressing low levels of myosin-binding protein C. CONCLUSIONS: Our method can measure the cardiac function of single micropatterned hiPSC-CMs and determine contractile parameters that can be used to elucidate mechanisms that underlie variations in CM function. This platform will be amenable to future studies of the effects of mutations and drugs on cardiac function.

Modeling and optimization of acoustofluidic micro-devices.

We investigate how the combination of numerical simulation tools and optimization routines can be used to design micro-devices. Experimental devices that are designed in this way can only provide optimal performance if the simulation model, used in the optimization procedure, reflects the real device characteristics accurately. Owing to this fact, the modeling of acoustofluidic devices is summarized. The mathematical formulation of the optimization problem, the parameterization of the device design and the implementation of the optimization loop is addressed alongside with practical recommendations for the chosen genetic algorithm optimization. In order to validate the implementation, an optimized planar resonator is compared with the optimal geometry given in the literature. The optimization of a typical 3D micro-device shows that devices can be designed to generate any desired acoustic mode shape at maximum pressure amplitude. The presented automatic design approach is of great practical relevance for the development of highly optimized micro-devices and it can speed up and facilitate the design-process in the growing field of acoustofluidics.