BLANKET AND PATTERNED REPROGRAMMING OF AZOPOLYMER NANORIDGES AND APPLICATIONS TO CELLULAR BIOPHYSICS

Abstract

The objective of this project is to tailor nanotopographies previously fabricated on large areas through photomodification. The original master patterns consist of nanoridges created using conventional lithography. Using an azopolymer as a photoresponsive material, replicas of the original master were prepared using soft lithography. The entire surface of the azopolymer nanoridges underwent photomodification using a 532 nm laser with varying polarizations and durations, in a process referred to as blanket reprogramming. This process resulted in controllable widening, buckling, or removal of the nanoridges due to photoisomerization and subsequent mass migration of the azopolymer. To replicate the reprogrammed surfaces, a molding procedure was employed using an acrylatic resin. The blanket reprogramming process was monitored in situ during exposure through diffraction of another reading laser beam. Cellular behaviors can be modulated in various biological contexts through interactions with their surroundings. The relationship between nanotopography and cell behavior is crucial, and has a wide range of biological consequences and medical applications. For example, nanotopography is employed to design antibacterial surfaces, preventing the adhesion of bacteria and biofilm formation, thereby reducing the risk of infections associated with medical devices. Nanostructured surfaces can inhibit the migration of cancer cells, offering insights into potential therapeutic strategies. Nanotopography is also used in nerve-regeneration scaffolds to guide neurite outgrowth, aiding in the repair of damaged neural tissue. We investigated the response of MCF10A breast epithelial cells to buckled acrylic nanoridges replicated from a master of azopolymer ridges photomodified by laser. The nanoridges became buckled after exposure to 532 nm light polarized parallel to the ridges. The impact of buckling on the dynamics and location of actin polymerization was investigated, as well as the distribution of lengths of contiguous polymerized regions. Azopolymers, known for their biocompatibility, have been employed by various research groups to create nanotopographies on which cells are plated and imaged. We conducted experiments using a spinning-disk confocal fluorescence microscope, testing exposure wavelengths ranging from 405 nm to 640 nm. Our objective was to assess the feasibility of live-cell imaging on azopolymer nanotopographies without inducing surface alterations. Our findings revealed the capability of live-cell imaging at high frame rates across a wide range of wavelengths. This result stands in contrast to prior studies, in which the selection of fluorescent dyes compatible with these materials was limited to those excited in the red spectrum and emitting in the near-infrared. I demonstrate that different patterns can be created through patterned reprogramming of the azopolymer nanoridges. A periodic arrangement of light strips was projected perpendicular to the ridges, thereby projecting an amplitude grating onto the azopolymer nanoridges. The spacing of this pattern can be adjusted by altering the mask or adjusting the magnification of the optical system. Furthermore, varying the direction of light polarization expands the potential for creating a wider variety of designs. Different types of reprogramming motifs can be implemented by projecting patterns at angles that are not perpendicular to the substrate, by tilting the incoming laser beam away from the horizontal. Various intriguing patterns, such as repeating curves, were observed, dependent on both the angle of the incident light and the direction of light polarization relative to the direction of the ridges.