Probing and using the dielectric properties of microtubules within Microsystems integrating microelectrodes


  • Contact Researcher: Fabrice MORIN, Dr.
  • Hosted LIMMS Japanese Laboratory: FUJII Lab. --- Microbiochemical Systems


Project Overview

  • Keywords
    • Microtubules
    • Dielectric properties
  • Context :
The project currently under way in the Fujita laboratory is related to the integration of molecular motors (proteins from the kinesin family) and micro-devices. This practical aim is also an opportunity to study physical properties of microtubules, which are of fundamental importance in medicine and biology.

From a fundamental point of view, much information is expected from the experiments enabled by the capture of a single MT on nano-tweezers. The capture in itself however, is challenging and will probably require integrating fluidic technologies to the current setup. As for the substrate-integrated microelectrodes, the fabrication process has been recently established and experiments will start as soon as possible.
  • Objectives :
Efficient integration of molecular motors into functional devices is hampered by the frailness of proteins and the fact that MTs can only be oriented on a substrate through cumbersome fluidic techniques. The practical aim of the present is to find new ways to orientate and immobilize MTs on a substrate in a controlled fashion, so that they can subsequently support directed transport. The approach chosen is to investigate the dielectric properties of MTs to try and get a handle on their polarity while they are still on solution. This investigation, in itself, is the fundamental part of the project.

Micro- and nano-fabrication techniques provide the means to produce suitable tools for probing dielectric properties of MTs through various approaches, such as MT dielectrophoresis, electrorotation of MTs, and direct electrical measurements (conduction and impednance) of MTs immobilized between electrodes. The present work focuses roughly on two practical approaches to achieve such experiments. In the first approach, a specially fabricated micro-actuator(Fig 3-a) is used to capture and study the properties of a single microtubule (this project is in collaboration with Pr. Hashiguchi of Kagawa University, and associate Pr. Yokokawa from Ritsumeikan University). The other approach aims at using substrate-integrated electrode in order to probe (and hopefully achieve) various effects such as: MT electro-rotation, steering through a drag force created by AC electro-osmotic flow during gliding assay, direct field-induced steering, and control of kinesin motor activity through field-effects.

  • Methods :
Microtubules (MTs) are cylindral polymeric constructs made of alpha- and beta-tubulin monomers. Structurally complex and functionally essential, MTs are a major component of the cellular cytoskeleton. Besides their contribution to the mechanical stability of the cellular structure, their implication in several physiological processes of major importance has been demonstrated in the past decade. In particular, MTs support active transport from the nucleus to distal parts of the cell body, in association with motor proteins such as kinesin and dynein. Disturbance of stability and functions of MTs results in major pathologies, such as Alzheimer’s disease. Research on MTs is thus of paramount importance.
Research on the link between MTs, motor proteins and intra-cellular transport has traditionally been carried out in vitro through two main techniques: gliding assays (whereby kinesin proteins are immobilized and support MT translocation on a substrate, Fig. 2-a) and beads assays (whereby MTs are immobilized onto a substrate and kinesin coated onto polystyrene beads which thus move along the MTs, Fig. 2-b).

The ability demonstrated during such assays by the pair MT/kinesin to carry loads at the nano-scale has recently attracted much attention insofar as it could be used for nano-assembly and nano-actuation. The Fujita laboratory has joined this area of research and has imported the techniques required for producing tubulin and kinesin. More specifically, previous and current work in the Fujita laboratory aims at harnessing the molecular tools required to obtain specific binding and directed transport of selected cargo.
Microtubules1.png Nanotweezer1.png
  • References :
  1. L. Jia, S.G. Moorjani, T.N. Jackson and W.O. Hancock, “Microscale transport and sorting by kinesin molecular motors”, Biomedical Microdevices 6:1, pp. 67-74, 2004.
  2. R. Yokokawa, Y. Yoshida, S. Takeuchi, T. Kon and H. Fujita, “Unidirectional transport of a bead on a single microtubule immobilized in a submicrometer channel”, Nanotechnology, Vol. 17, pp. 289-294, 2006.
  3. M.C. Tarhan, R. Yokokawa, F. Morin, S. Takeuchi, T. Gon and H. Fujita, “Carrying target molecules on beads by bio-molecular motors”, to appear in Proceedings of MEMS 2006.
  4. M. Hosogi, G. Hashiguchi, F. Asao, J. Yamamoto, T. Goda, K. Hirano, Y.Baba, K. Kakushima, and H. Fujita, Narrow gap DNA tweezers for short DNA molecules”, SPIE proceedings, 2004.