In situ photopatterning of cell laden biomaterials for spatially organized 3D cell cultures in a microfluidic chip

Micropatterning techniques for 3D cell cultures enable the recreation of tissue-level structures, but their combination with well-defined, microscale fluidic systems for perfusion remains challenging. To address this technological gap, we developed a user-friendly in-situ micropatterning protocol that integrates photolithography of crosslinkable, cell-laden hydrogels with a simple microfluidic housing, and tested the impact of crosslinking chemistry on stability and spatial resolution. Working with gelatin functionalized with photo-crosslinkable moieties, we found that inclusion of cells at high densities ([≥] 107/mL) during crosslinking did not impede thiol-norbornene gelation, but decreased the storage moduli of methacryloyl hydrogels. Hydrogel composition and light dose were selected to match the storage moduli of soft tissues. The cell-laden precursor solution was flowed into a microfluidic chamber and exposed to 405 nm light through a photomask to generate the desired pattern. The on-chip 3D cultures were self-standing, and the designs were interchangeable by simply swapping out the photomask. Thiol-ene hydrogels yielded highly accurate feature sizes from 100 - 900 m in diameter, whereas methacryloyl hydrogels yielded slightly enlarged features. Furthermore, only thiol-ene hydrogels were mechanically stable under perfusion overnight. Repeated patterning readily generated multi-region cultures, either separately or adjacent, including non-linear boundaries that are challenging to obtain on-chip. As a proof-of-principle, primary human T cells, were patterned on-chip with high regional specificity. Viability remained high (> 85%) after overnight culture with constant perfusion. We envision that this technology will enable researchers to pattern 3D cultures under fluidic control in biomimetic geometries that were previously difficult to obtain.