Conclusions
In this study, we demonstrated a new strategy for improving cellular assembly and functions inside human cell-based spheroids via synergistically promoting biophysical and biochemical cues using engineered MPs. Our MPs integrated covalently attached PFC groups and ECM adhesive ligands on the surface to enhance oxygen tensions internally while improving cell/tissue architecture and functions, respectively. We confirmed the value of PFC-MPs for dissolving and releasing oxygen to enhance oxygen tensions at the cellular level using a RuDPP oxygen sensitive dye with microscopy-based fluorescence sensing. We next observed that cells in assembled liver spheroids responded best to MPs presenting laminin-511 and -521 ECM proteins, which are more prevalent in the mature liver as compared to laminin-111. These laminin isoforms encouraged enhanced phenotypic liver spheroid formation with up-regulation of E-cadherin and vinculin expression, as well as greater albumin and urea secretion as compared to MPs presenting other ECMs and the controls. HSCs also arranged in native liver type arrangements when laminin 511/521 conjugated MPs were used as compared to laminin-111, fibronectin, and control groups; providing evidence that ECM proteins have distinct roles in the phenotypic regulation of mature liver derived cells. In conclusion, via synergistic enhancement of internal oxygen availability as well as presentation of specific ECM cell adhesion ligands, our engineered MP approach provides a unique tool to help cells to assemble in a more native 3D microenvironment within spheroids, thereby improving in vitro modeling applications such as in the first stages of drug development or for personalized drug screening applications.