PnBA/PDMAA-Based Iron-Loaded Micropillars Allow for Discrete Cell Adhesion and Analysis of Actuation-Related Molecular Responses

A new approach to generate magneto-activatable microstructures for discrete cell adhesion to investigate cell mechanoresponsiveness is reported here. The system is based on poly(n-butylacrylate) micropillar arrays, generated from prepolymers via C,H insertion chemistry and filled with magnetic iron oxide nanoparticles. The pillars' surfaces are modified such that only top faces of the pillars are cell attractive, while the pillar side walls and the area between the pillars are covered by a cell repelling hydrogel layer based on poly(N,N-dimethyl acrylamide). Magnet stimulation leads to pillar deflection, which induces traction forces to adherent cells. Analysis of early mechanoresponse in human mesenchymal stem cells, specifically the localization of autophosphorylated focal adhesion kinase (pFAK Y397) and the co-transcriptional activator yes-associated protein (YAP), shows a clear redistribution of pFAK Y397 to the cell margins and an enhanced nuclear localization of YAP, following the magnetically induced mechanical actuation. The successful use of this technique shows that the generated magnetoactive posts are suitable tools to detect the onset (FAK) and maintenance (YAP) involved in stem cell mechanosensing and mechanotransduction. The platform combines selective cell adhesion with the possibility of magnetic actuation, thereby representing a promising technology to broaden the molecular understanding of cellular mechanobiology.