Yoshitake Akiyama

Fabrication and Evaluation of Reconstructed Cardiac Tissue and Its Application to Bio-actuated Microdevices

In this paper, we proposed to utilize a reconstructed cardiac tissue as microactuator with easy assembly. In a glucose solution, cardiomyocytes can contract autonomously using only chemical energy. However, a single cardiomyocyte is not enough to actuate a microrobot or a mechanical system. Though the output power will increase by using multiple cardiomyocyte, it is difficult to assemble those cardiomyocyte to predefined positions one-by-one using a micromanipulator. Reconstructed cardiac tissue not only will enable researchers to assemble the cells easily and but also has a potential to improve the contractile ability. To realize a bio-actuator in this paper, we reconstructed a microcardiac tissue using an extracellular matrix, and their displacements, displacement frequency, contractile force, and lifetime of the reconstructed cardiac tissue were evaluated. Electrical and pharmacological responses of the reconstructed cardiac tissue were also evaluated. Finally, a bioactuator, a primitive micropillar actuator, was fabricated and applicability of the reconstructed cardiac tissue for bioactuators was evaluated.

Biological contractile regulation of micropillar actuator driven by insect dorsal vessel tissue

This paper examines biological regulation of micropillar actuation by insect dorsal vessel tissue. Micromechanical devices using mammalian cardiomyocytes have been reported, but they work only at only at 37degC and at pH of around 7.4. On the other hand, insect cells can survive and proliferate at 20 to 30degC and at pH 6 to 8. We have already proposed utilization of insect heart tissue as a bio-actuator and demonstrated a micropillar actuator. For practical use, a regulation technique should be developed. It was reported that two neuropeptides, proctolin and crustacean cardioactive peptide CCAP could accelerate heart beat. In this study, addition of CCAP at 10-6 M accelerated the frequency of the micropillar actuation 5.6-fold from 0.11 to 0.62 Hz and it returned to nearly the original value in 5 min. Proctolin addition up to 10-5 M had little effect on the actuation. These results showed that CCAP is useful in frequency regulation of a bio-actuator driven by dorsal vessel tissue.

Construction of Regenerative Mechanical Systems of Insect Cells for a Quasi-Living Machine

Here we propose the regenerative mechanical system for a quasi-living machine. As a first step toward the realization of this system, the larvae of two lepidopteran species, bombyx mori (BM) and thysanoplusia intermixta (TI) were dissected and their tissues were cultured. The removed TI dorsal vessels kept beating spontaneously and vigorously for three days and beating weakly more than three weeks. The removed BM ones beat weakly or nothing. It is essential for tissue reconstruction at the cell level to obtain and culture the cells of these tissues. The TI dorsal vessel cells were obtained by collecting the migrating cells from the tissues and the BM dorsal vessel cells were obtained by enzymatic dissociation of the tissues. In this study, the spontaneous beatings of both dorsal vessel cells were not observed. These experimental results suggest the possibility of construction of a regenerative microrobotic system with living components in future

Size fractionation of primary muscle cells using hydrodynamics in microchannels

A microfluidic device based on hydrodynamic fractionation by size was applied for enrichment of muscle precursor cells obtained from heterogeneous primary cells of muscle tissues. In this paper, the relationship between cell size and quality of regenerative muscles in vitro was focused on. Fractionation of primary cells from rat limbs was demonstrated using a microfluidic device based on hydrodynamics in the microchannels. The precise size sorting of cells was achieved. Observations of each cell fraction showed smaller cells had high activity for muscle differentiation. This suggested the good potential for cell processing by size fractionation using a microfluidic device for tissue engineering in regenerative medicine.

Miniaturized mechano-bionic systems with a muscle-powered bioactuator

Biological cells have a variety of high performance functions using chemical energy from oxygen and nutrients and no electrical energy. We have proposed a novel use of pulsating heart cells as mechanical micro actuators. Here we propose a novel bio-actuated power generator combined with the contractile force of heart muscle cells and piezoelectric fiber as a material combination to convert vibrational energy into electrical energy. Further, we propose a novel design for a tube-type micropump powered by the contractile force of heart muscle cells. In this paper, these principles and the prototypes are shown.