Figure 2.

Effects of PHH homotypic interactions within microtissues on liver functions. Collagen-based microtissues containing increasing densities of PHHs in a pH-neutralized collagen (1.25e6 and 2.5e6 cells/ml) solution were fabricated using the droplet microfluidic device shown in Figure 1. Representative phase-contrast images of PHH microtissues with a density of (a) 1.25e6 cells/ml and (b) 2.5e6 cells/ml placed within agarose microwells cast within 24-well plates. Both 1.25e6 and 2.5e6 cells/ml densities produced reproducible microtissues with high yields that fit within the 300 μm × 300 μm agarose microwells. (c) Albumin production and CYP3A4 enzyme activity for PHH microtissues fabricated using a cell density of 1.25e6 and 2.5e6 cells/ml. Microtissues with 3.75e6 and 5e6 cells/ml densities were also fabricated, but these densities did not produce homogenously sized microtissues (not shown). Statistical significance is displayed relative to 1.25e6 cells/ml at the same time point. ***p ≤ 0.001.