Direct Micropatterning of Extracellular Matrix Proteins on Functionalized Polyacrylamide Hydrogels Shows Geometric Regulation of Cell–Cell Junctions

Microcontact printing of extracellular matrix (ECM) proteins in defined regions of a substrate allows spatial control over cell attachment and enables the study of cellular response to irregular ECM geometries. Over the past decade, numerous micropatterning techniques have emerged that conjugate ECM proteins on hydrogel substrates of tunable stiffness, which have revealed a range of cellular responses to varying matrix stiffness and geometry. However, micropatterning of ECM proteins on polyacrylamide (PA) hydrogel remains inconsistent due to its unreliable conjugation with the commonly used protein cross-linkers, particularly at low stiffness. To address these problems, we developed a micropatterning technique in which the PA gel is functionalized by incorporating oxidized N-hydroxyethylacrylamide, which allows direct protein binding through reactive aldehyde groups without any exogenous cross-linkers. As a result, a uniform and consistent protein transfer onto the hydrogel substrates of defined geometrie...