Simultaneous and bidirectional transport of kinesin‐coated microspheres and dynein‐coated microspheres on polarity‐oriented microtubules

Artificial nanotransport systems inspired by intracellular transport processes have been investigated for over a decade using the motor protein kinesin and microtubules. However, only unidirectional cargo transport has been achieved for the purpose of nanotransport in a microfluidic system. Here, we demonstrate bidirectional nanotransport by integrating kinesin and dynein motor proteins. Our molecular system allows microtubule orientation of either polarity in a microfluidic channel to construct a transport track. Each motor protein acts as a nanoactuators that transports microspheres in opposite directions determined by the polarity of the oriented microtubules: kinesin‐coated microspheres move toward the plus end of microtubules, whereas dynein‐coated microspheres move toward the minus end. We demonstrate both unidirectional and bidirectional transport using kinesin‐ and dynein‐coated microspheres on microtubules oriented and glutaraldehyde‐immobilized in a microfluidic channel. Tracking and statistical analysis of microsphere movement demonstrate that 87–98% of microspheres move in the designated direction at a mean velocity of 0.22–0.28 µm/s for kinesin‐coated microspheres and 0.34–0.39 µm/s for dynein‐coated microspheres. This bidirectional nanotransport goes beyond conventional unidirectional transport to achieve more complex artificial nanotransport in vitro. Biotechnol. Biotechnol. Bioeng. 2008;101: 1–8. © 2008 Wiley Periodicals, Inc.