Building cell-containing multilayered phospholipid polymer hydrogels for controlling the diffusion of a bioactive reagent

Cytocompatible and multilayered phospholipid polymer hydrogels containing living cells and a specific bioactive reagent were used to determine the role of diffusion of a bioactive reagent in regulating cell-fate. Within the multilayered hydrogels prepared by a layer-by-layer assembling process, a bioactive reagent reservoir layer and a cell-laden layer were separated with a finely formed dual-crosslinked hydrogel multilayer that was composed of a 2-methacryloyloxyethyl phosphorylcholine polymer and photo-reactive poly(vinyl alcohol). The dual-crosslinked hydrogel was less permeable than the single-crosslinked hydrogel and thus served as a diffusion-controlling barrier. We demonstrated the use of this multilayered hydrogel by subjecting the human cervical cancer HeLa cell-line to paclitaxel. We found that cell viability was regulated by the thickness of the diffusion-controlling barrier and the bioactive reagent concentration. An increase in the barrier thickness and a decrease in the bioactive reagent concentration resulted in decreased apoptosis of the HeLa cells. Our results suggest that the gradient of a bioactive reagent formed was due to the diffusion-controlling barriers, which explains the observed diffusion-dependent cell behavior. This study provides insight into the regulation of bioactive reagent diffusion in micrometer scale hydrogels and the associated diffusion-dependent effects on cell behavior. This finding can contribute to the design of a platform for studying diffusion-dependent cell behavior for tissue engineering and regenerative medicine applications.