Comparative study of visible light polymerized gelatin hydrogels for 3D culture of hepatic progenitor cells

Abstract

Photopolymerization techniques have been widely used to create hydrogels for biomedical applications. Visible light-based photopolymerizations are commonly initiated by type II (i.e., noncleavage-type) photoinitiator in conjunction with a coinitiator. On the other hand, type I photoinitiators (i.e., cleavage type) are rarely compatible with visible light-based initiation due to their limited molar absorbability in the visible light wavelengths. Here, we report visible light initiated orthogonal photoclick crosslinking to fabricate gelatin-norbornene and poly(ethylene glycol)-tetra-thiol hydrogels using either cleavage-type (i.e., lithium acylphosphinate, LAP) or noncleavage-type photoinitiator (i.e., eosin-Y, EY) without the use of a coinitiator. Regardless of the initiator type, the step-growth gelatin-PEG hybrid hydrogels crosslinked and degraded similarly. While both systems exhibited similar cytocompatibility for hepatic progenitor HepaRG cells, gelation initiated by noncleavage-type initiator EY afforded slightly higher degree of hepatic gene expression.