Long-term cultivation of HepG2 liver cells encapsulated in alginate hydrogels: A study of cell viability, morphology and drug metabolism

In this study, we have evaluated the use of ultra-sterile alginate hydrogels encapsulated with HepG2 liver cells for applications in high throughput drug screening. We have studied the cellular viability and metabolic capacity of the encapsulated cells in two different alginate structures SLM100 (G:M::40:60) and SLG100 (G:M::60:40). We have also developed protocols to characterize the encapsulated cells within the alginate structure using scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). Further we have studied the Phase-I/II metabolic characteristics of the encapsulated cells in monolayer and 3D culture. Our results indicate that cells encapsulated within SLM100 and SLG100 class of alginates have shown high cellular viability with >80% even after 14 days in culture. As expected, the proliferation rates of the encapsulated cells are held steady and do not proliferate within the gels. Production of liver-specific enzymes such as CYP1A1 and CYP3A4 after 14 days in culture indicates the viability and functionality of the encapsulated HepG2 cells. Phase-II Glutathione activity of the encapsulated cells were also maintained in 3D culture conditions. The encapsulated cells within the 3D gels were also capable of metabolizing the pro-drug EFC (7-ethoxy-4-trifluoromethyl coumarin) to HFC (7-hydroxy-4-trifluoromethyl) in a linear fashion over a period of time. These results have provided us with baseline results to benchmark future improvements in material and design configurations for optimal pharmacokinetic response of in vitro tissue model systems.