Surface manipulation of microtubules using self-assembled monolayers and electrophoresis

We integrate microtubule (MT)-resistant self-assembled monolayers (SAMs) with lithographically patterned electrodes to control MTs in a cell-free environment. Formed through a facile, one-step assembly method, the poly(ethylene glycol) trimethoxysilane SAM prevents MT adsorption on both silicon substrates and Au microstructures without casein. We characterize the SAM using ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy and compare it with other MT passivation techniques. The SAM retains its passivating ability when used as a substrate for electron beam lithography, a key feature that allows us to pattern microtubules on lithographically defined Au structures. Moreover, by combining the SAM-passivated Au microelectrodes and DC electrophoresis, we demonstrate reversible trapping of MTs as well as capture and alignment of individual MTs.