Isometric contraction force measurement of hiPSC-CMs on a movable plate with a feedback-controlled MEMS cantilever probe

Abstract

We propose a measurement method with a feedback system to evaluate the contraction forces of human iPS cell-derived cardiomyocytes (hiPSC-CMs) in a dynamic mechanical environment. The measurement of the hiPSC-CM contraction forces is important for regenerative medicine; however, conventional methods are not able to evaluate these forces when the cells are subjected to a dynamic load similar to that from the heart. The proposed measurement system is composed of a micromachined piezoresistive cantilever attached to a feedback-controlled piezo stage and a micromachined movable plate where cells are cultured. A high sampling rate (2 kHz) and real-time control of the cell length were realized via the feedback-controlled piezo stage, while the contraction forces were measured by the cantilever. We evaluated the contraction forces of hiPSC-CMs in conditions of isometric and auxotonic contractions. Due to feedback-controlled loading for isometric contraction, the cell shrinkage was controlled to be less than 200 nm. Auxotonic contraction forces of 3.9 μN were measured without feedback control, while the contraction forces of isometric contraction were 6.0 μN with feedback-controlled loading. The results showed that the method leads to a work-loop evaluation of the hiPSC-CM cardiac cycle.

Temperature Dependence of the Beating Frequency of hiPSC-CMs Using a MEMS Force Sensor

“…However, to investigate the magnitude of the displacement, it is necessary to return to the original data in Figure 5 A, and the displacement was estimated to be approximately 10 µm at 24 °C. The spring constants of the movable plate and force sensor were 2.54 N/m and 0.72 N/m, respectively, with a combined spring constant of 3.26 N/m [ 20 ]. Thus, a displacement of 10 µm corresponded to a force of approximately 33 µN.…”

“…We used MEMS-based cantilever force sensors to investigate how the beating frequency of hiPSC-CMs changes with temperature. The use of silicon-based force sensors for studying cellular forces has advantages in terms of temporal resolution [ 18 , 19 , 20 , 30 , 31 ]. Silicon-based force sensors have temporal resolutions in the order of GHz, and it has been reported that the force can be measured in units of adhesive spots on cells because of their high measurement speed of 400 kHz [ 31 ].…”

“…An overview of the measurement system [ 19 , 20 ] used in this experiment is shown in Figure 1 . The system consisted of a piezoresistive cantilever-type force sensor, a movable plate for culturing cells, a piezoelectric stage (B17-090, Nano Control Co., Ltd., Tokyo, Japan) for adjusting the sensor position, a piezo controller (NCS 6121C, Nano Control Co., Ltd., Tokyo, Japan), a field-programmable gate array (FPGA) (cRIO-9030, National Instruments, Austin, TX, USA) for controlling the piezoelectric stage and acquiring data, and a host PC for managing the FPGA and recording data.…”

“…In detail, we applied a stretch stimulus to hiPSC-CMs and measured the force–length relationship with a MEMS force sensor to evaluate the relationship between the stimulus and the contractile force [ 19 ]. In turn, we used the measured force to induce isometric and auxotonic contractions in hiPSC-CMs by controlling the strength of the stretch stimulus [ 20 ].…”