Engineered networks of oriented microtubule filaments for directed cargo transport.

Nature uses networks of oriented filaments to guide intracellular movement of cargo. We describe the first method for designing and constructing interconnected networks of oriented microtubules to create a two-dimensional in vitro transport system. Microfabricated open channels with surface-bound kinesin motor proteins are used to orient short microtubule seeds relative to each other. Guided by the channel geometry, the oriented microtubule seeds are then grown into oriented networks of microtubules, which support motility of kinesin-coated nanospheres with a directional preference determined by the microtubule orientation. In contrast to in vitro gliding motility assays where microtubules glide on kinesin-coated surfaces, engineered stationary microtubule networks could simultaneously utilize different motors, e.g. motors walking in opposite directions. Different motors, via their specific scaffolding proteins, could be utilized to selectively transport specific cargos. The presented method is the first step towards building oriented and interconnected microtubule networks with a user-designed geometry at the micron and submicron scale. The resulting platform enables multiple applications, from cargo sorting to adaptive camouflage.