Keitaro Ito

Single cell separation by using accessible microfluidic chip

Here we proposed a novel device named CACS (Convective Accumulation-based Cell Separator) system that is composed of a cell-trapper unit with accessible (open-structured) microfluidic device and a cell-picker device with high aspect ratio PDMS pillars. Utilizing this systematic instrument, we demonstrated proof-of-concept for cell separation through the process of (1) single cell trap in a well (2) single cell picking by pillar-based tweezers and (3) cell recovery. The optimized system for mammalian cells had enabled us to trap-in and pick-up target cells in 100% efficiency as far as tested. Moreover, picked cells showed 74.5% viability, as a result of a less-invasive cell separation technique. Furthermore, a series of different PDMS pillars indicated their varied efficiency in pick-up and recovery steps. We also found out that the aspect ratio of PDMS pillar is critical for tweezing a cell of interest. To improve on the performance of CACS system, further tuning is necessary, especially on the recovery unit for achieving an efficient and damage-free separation. Though CACS system shows low-throughput at this moment, its simplicity is applicable for any cell type by optimizing each pipeline.

Mechanical characterization system using on-chip probe with wide range actuation

In this paper, we focus on mechanical characterization of human umbilical vein endothelial cell(HUVEC) and mesenchymal stem cell(MSC) co-cultured spheroids. HUVEC/MSC co-cultured spheroid has a characteristic that the size becomes compact with culture day increase. In order to measure the mechanical characteristics of size changing spheroids, we apply whole chip deformation mechanism to the actuation method of on-chip probes for wide range actuation. Finally, we evaluate the stiffness of spheroids by using stiffness-index.

Stiffness-index map based on single cell-spheroid analysis using robot integrated microfluidic chiip

We present a method which can evaluate stiffness of cell-spheroids, and show the measurement results of the stiffness changes with respect to the culture time. To obtain the stiffness-index map, where the map shows the relationship between the size and stiffness of cell-spheroids, we applied on-chip measurement method using a robot integrated microfluidic chip (robochip). The robochip has a microchannel and a pair of on-chip probes which contains a force sensor. By measuring the stiffness in microfluidic channel, we can achieve a stable and high-throughput evaluation of mechanical characteristics. The stiffness of the single spheroid is evaluated from the reactive force when the target spheroid is deformed by the on-chip probes. The stiffness-index of cell-spheroid is proposed, and the evaluation results of the stiffness index shows that the index increased along the culture days. The proposed system will provide us a new index for the cell-quality evaluation.

Temporal Transition of Mechanical Characteristics of HUVEC/MSC Spheroids Using a Microfluidic Chip with Force Sensor Probes

In this paper, we focus on the mechanical characterization of co-cultured spheroids of human umbilical vein endothelial cells (HUVECs) and mesenchymal stem cells (MSC) (HUVEC/MSC spheroids). HUVEC/MSC spheroids aggregate during culture, thereby decreasing in size. Since this size decrease can be caused by the contractility generated by the actomyosin of MSCs, which are intracellular frames, we can expect that there is a temporal transition for the mechanical characteristics, such as stiffness, during culture. To measure the mechanical characteristics, we use a microfluidic chip that is integrated with force sensor probes. We show the details of the measurement configuration and the results of mechanical characterization of the HUVEC/MSC spheroids. To evaluate the stiffness of the spheroids, we introduce the stiffness index, which essentially shows a spring constant per unit size of the spheroid at a certain time during measurement. From the measurement results, we confirmed that the stiffness index firstly increased during the days of culture, although after four days of culture, the stiffness index decreased. We confirmed that the proposed system can measure the stiffness of HUVEC/MSC spheroids.

On-chip monitoring of megakaryocytes in shear flow environment

We propose on-chip monitoring system for production process of platelets in a microfluidic chip. The applied pressure condition to microfludic channel can be controlled. In this study, we demonstrated the on-chip monitoring and confirmed that proplatelet was generated.

Mechanical characterization of floating cell using whole chip deformation mechanism

We present a method of cell mechanical characterization using a robot integrated microfluidic chip (robochip). The robochip has a microchannel, a force sensor and an on-chip probe. On-chip probe is actuated by whole chip deformation mechanism. Firstly, we designed the robochip. Secondary, we fabricated the robochip. Finally, we measured the youngs modulus of zona pellucida by using Hertz contact theory.

Integration of microvalves using thermoresponsible photo-processible gel actuator

We present an innovative gel actuator made of photo-processible thermoresponsible gel. (Fig. 1) We evaluated integratability of the gel actuator by experimentally and theoretically and confirmed that it is possible to integrate within 100 μm. We performed demonstration of integrated valves fabricated on five branched microchannel.