Designing 3D fiber reinforced hydrogels for in vitro cell studies

Abstract

The extracellular matrix (ECM) is known to play an important role in the health of cells and tissues. Not only are chemical signals transmitted via bonds and tightly controlled diffusion, but the structure of the ECM also provides important physical signaling for the cells attached to it. The structure is composed of a mesh of fibrous proteins, such as collagen, embedded in a hydrated gel matrix of glycosaminoglycans. Most of the cell culture matrices are single-phase bio- or polymeric hydrogels. Therefore, here a continuous hybrid manufacturing process was developed to make fiber-reinforced composite hydrogels. A far field electrospinning process was used to deposit the fibrous component with the aid of guiding electrodes; and a gravity-assisted, droplet-based system controlled the rate of addition of the cell-laden hydrogel component. The addition of the fibrous component slightly increased the elastic modulus of the pure hydrogel and the cells that were embedded into the fiber-reinforced hydrogels remained viable for 8 days. The cells were randomly placed in the matrix such that some had no contact to the fibers and others were initially in proximity to fibers. Without fiber interaction, cells grew into spheroidal clusters within the hydrogel, while those in proximity to the fibers spread out and grew along the fibers, showing that the fiber-reinforced hydrogels are able to control cell behavior with morphological cues. Additional 2D testing was done with and without the addition of collagen, to test the polymer composition effects on cell adhesion. Initial testing showed no statistical difference between a purely synthetic solution and a solution mixed with the biological component of collagen. As a result, all 3D tests were run with the unmodified synthetic polymer, without the addition of collagen.

ABSTRACT