Collagen/poloxamine hydrogels: Cytocompatibility of embedded HepG2 cells and surface-attached endothelial cells

The effects of cross-linked poloxamine hydrogels on the cellular function of embedded HepG2 cells and surface-attached endothelial cells were assessed. HepG2 cells embedded within collagen/poloxamine-methacrylate gel survived photo-cross-linking (MTT viability, 78%). There was a gradual increase in cell number during the first week. The cumulative secretion of α₁- antitrypsin by HepG2 cells showed an almost linear profile. However, lower levels for the collagen/poloxamine-methacrylate matrix were observed when compared with collagen. Endothelial cells attached poorly to poloxamine gels without collagen (alamarBlue reduction ranged from 36 to 63%) and did not spread well. The addition of collagen led to spread cells and alamarBlue reduction levels of 75-93% (24 h after seeding). On day 5, some detachment was noted through analysis of vascular endothelial cadherin staining. Finally, the collagen-containing matrix was used to prepare cylindrical modules containing HepG2 cells to show the utility of this material in modular tissue constructs. A fluorescent cytoplasmic tracer, Vybrant CFDA SE, showed that embedded cells remained viable for more than 2 months, confirming the good cytocompatibility of collagen/poloxamine-methacrylate in the form of modules. The suitability of these modules for preparing uniform, scaleable, and vascularized constructs remains to be demonstrated.