Reversible holographic patterns on azopolymers for guiding cell adhesion and orientation

Topography of material surfaces is known to influence cell behavior at different levels: from adhesion up to differentiation. Different micro- and nano-patterning techniques have been employed in order to create patterned surfaces to investigate various aspects of cell behavior, most notably cellular mechanotransduction. Nevertheless, conventional techniques, once implemented on a specific substrate, fail in allowing dynamic changes of the topographic features. Here we investigated NIH-3T3 cell response to reversible topographic signals encoded on light responsive azopolymer films. Switchable patterns were fabricated by means of a well established holographic set-up. Surface relief gratings (SRGs) were realized with Lloyd's mirror system and erased with circular polarized or incoherent light. Cell cytoskeleton organization and focal adhesions assembly proved to be very sensitive to the underlying topographic signal. Thereafter, pattern reversibility was tested in air and wet environment by using temperature or light as triggers. Additionally, pattern modification was dynamically performed on substrates with living cells. This study paves the way towards an in-situ and real-time investigation of the material-cytoskeleton crosstalk owing to the intrinsic proprieties of azopolymers.