Hepatocyte viability and protein expression within hydrogel microstructures

Poly(ethylene) glycol (PEG) hydrogels have been successfully used to entrap mammalian cells for potential high throughput drug screening and biosensing applications. To determine the influence of PEG composition on the production of cellular protein, mammalian hepatocytes were maintained in PEG hydrogels for 7 days. Total cell viability, total protein production, and the production of two specific proteins, albumin and fibronectin, were monitored. Studies revealed that while PEG composition has no effect on cell viability, increasing amounts of PEG in the hydrogel decrease the amount of protein production by the cells after 7 days from 1.0 × 10⁵ ± 1.7 × 10⁴ to 5.2 × 10³ ± 1.3 × 10³ g accumulated protein/mL/million cells. Additionally, cells entrapped in PEG hydrogels produce greater amounts of protein than traditional monolayer culture (1.5 × 10³ ± 1.9 × 10² g accumulated protein/mL/million cells after 7 days). The addition of the synthetic peptide RGD to 10% PEG hydrogels altered the production of the proteins albumin and fibronectin. Hydrogels with the RGD sequence produced 287 ± 27 ng/mL/million cells albumin after 7 days, an order of magnitude greater than monolayer cultures, whereas cells in hydrogels without the RGD sequence produced undetectable levels of albumin. Conversely, cells entrapped in 10% PEG hydrogels without the RGD sequence produced 1014 ± 328 ng/mL/million cells fibronectin after 7 days, whereas 10% PEG hydrogels with the RGD sequence produced 200 ± 58 ng/mL/million cells fibronectin after 7 days.