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.