In the first part, we demonstrate that pattern dimensions regulate the degree of alignment in human cardiomyocytes (hCMs) and human cardiac fibroblasts (hCFs). Higher alignment is achieved with increased pattern amplitude or reduced wavelength. By spatially tuning lamellar patterns, we generate both distinct regions and continuous gradients of alignment. Furthermore, we fabricate micro-well array devices with custom lamellar bottom patterns for high-throughput screening. Initial results show that increasing seeding density significantly reduces cellular alignment, highlighting the importance of microenvironmental design. Notably, this system supports co-culture of hCMs and hCFs where the cell ratio is decoupled from alignment effects.
In the second part, we present a dynamic stiffening hydrogel platform, created through a stepwise approach involving chemical addition and light-mediated crosslinking, integrated with an elastomeric substrate featuring strain-responsive surface topographies. Using this platform, we explore the response of human induced pluripotent stem cell-derived cardiomyocytes (hIPSC-CMs) to progressive matrix stiffening from healthy to fibrotic levels. Cells cultured on healthy stiffness show enhanced maturation, indicated by greater sarcomere fraction, wider sarcomere width, elevated connexin-43 expression, and increased beating frequency compared to those on fibrotic matrices. Importantly, early stiffening events exert a more substantial negative impact on hIPSC-CM function than late-stage stiffening.
Together, these findings offer novel insights into how biomaterial design can direct cellular behavior and maturation in engineered cardiac tissues. Beyond the heart, this work informs strategies in tissue models for muscle, tendon, nerve, and cornea, where alignment and stiffness dynamics are equally critical for development and regeneration.