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Research

 Yokokawa group focuses on the development of innovative micro/nano-fabricated devices (microfluidic devices) with applications in medicine, pharmacology and biology. Central to our vision is to promote the synergy effect in our group. It will deepen our understandings of various biological functions and mechanisms at the micro/nano-scale in an interdisciplinary research milieu by converging engineering, life sciences, and physical sciences. It will contribute to provide solutions for the improvement of quality of life (QOL) and treatment/diagnosis of diseases by personalized medicine in the globally. The group is committed to the achievement of the intellectual vision through organs-on-a-chip (micro-physiological systems) and biophysics of motor proteins.

  1. Organ-on-a-Chip for kidney physiological functions
  2. Perfusable on-chip vascular network for mechanobiology and organogenesis applications
  3. Biophysics of motor proteins on micro/nano-fabricated substrates

 

1.Organ-on-a-Chip for kidney physiological functions

 Miniaturized Organ-on-a-Chip (OoC) platforms enable replicating the physiological functions of human organs by simulating cell-cell interaction / physical stimulation using microfluidic techniques. Using OoC technology, we focus on developing microfluidic devices that can mimic the physiological functions of kidney, including but not limited to blood filtration and reabsorption. We intend to employ these OoC devices to accelerate drug discovery research that in general require long-term screening and nephrotoxicity tests in supplement development.

R. B. Sadeghian et al., The 22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences (MicroTAS 2018), Kaohsiung, Taiwan, 2018.

 

2.Perfusable on-chip vascular network for mechanobiology and organogenesis applications

 Micro fabrication enables three-dimensional (3D) culture models that mimic the cellular functions of living tissues. Although many 3D models have been developed including organoids and spheroids, most of them lack pefusable vasculatures for the long-term culture. We developed a method to induce a vascular network in a spheroid made of human lung fibroblasts (hLFs) and human umbilical vein endothelial cells (HUVECs). The network has luminal structure and opened to micro channels, which can be used for supplying medium and drug. The culture system provides a new platform in drug discovery, pharmacokinetics and developmental biology

Y. Nashimoto et al., J. Vis. Exp., 134, e57242, 2018.
Y. Nashimoto et al., Integr. Biol., 9, 6, 506-518, 2017.

 

3.Biophysics of motor proteins on micro/nano-fabricated substrates

 In vivo, cells and proteins are constantly moving. We are aiming to use motor proteins as actuators of micro/nanomachines in vitro. We also are developing new micro/nano devices for investigating biophysics of proteins. For example, we developed a microdevice for investigation of the walking mechanism of motor proteins and cooperativity of multiple motor proteins.

3-1.Control of microtubule gliding direction.

 When a microtubule glides on a kinesin-coated surface, their leading tip experiences Brownian motion due to the thermal fluctuation, and then find the next kinesin to bind. We focused on the electrophoretic and mechanical properties of microtubules to control their gliding directions in an electric field. Two microtubules were successfully guided toward two identical directions, which can be applied to nano-transport systems. (by collaboration with Porf. E. Meyhofer @ U. Michigan, Prof. J. L. Ross @ U. Massachusetts, Prof. T. L. Hawkins @ U. Wisconsin)

N. Isozaki et al., Sci. Rep., 5, 7669, 2015.
N. Isozaki et al., Sci. Robot., 2, 10, eaan4882, 2017.

3-2.Visualizing molecular binding carried by kinesin and dynein motors.

 Do we really need buffer solutions to initiate chemical reactions? As motor proteins can carry individual molecules along microtubules, we designed a molecular assay that enables to visualize molecular bindings of GST-GSH and avidin-biotin. Each affinity molecule was carried by kinesin and dynein on a microtubule, respectively, and colocalized at their collision during their transport.

K. Fujimoto et al., ACS Nano, 7, 447455, 2013.

3-3.Dynamic PDMS channel for active transport by motor proteins.

 It is hard to recognize whether a target molecule is carried by the active transport driven by motor proteins or just by free diffusion in a microfluidic channel. We developed a dynamic PDMS channel that enables to close the assay area by actuating a thin PDMS membrane to focus on the active transport. Along with the numerical calculation, the research illustrated how motor proteins actively transport molecules in a microfluidic device.

K. Fujimoto et al., Lab Chip, 15, 2055-2063, 2015.