Production of hyaluronic acid-acrylamide microgels as potential cell culture scaffolds

Hyaluronic acid (HA) derived hydrogels give support and structure for cultured cells in 3D environments that better mimic in vivo conditions 1. Adequate diffusion of oxygen and nutrients however, is generally limited to a depth of 200 µm in bulk hydrogels 2, limiting their applicability to larger size constructs. Through droplet-based microfluidics we produced monodisperse HA-derived microgel droplets. Hyaluronic acid acrylamide (HA-am) was synthesized by partially modifying high molecular weight sodium hyaluronan with a N-(2-aminoethyl)acrylamide linker to a 20% degree. Gel droplets were produced in a PDMS microfluidic device designed in a flow focusing geometry. In this setup polystyrene beads were added to simulate cell-encapsulation into a matrix that would better reflect in vivo conditions. The hydrogel precursor mixtures were prepared with 2% solution of HA-am and a photoinitiator with the addition of polystyrene beads (10µm in diameter) at a concentration of 10 million beads per milliliter. A fluorinated oil (Novec 7500, 3M) with 0.5% surfactant (PicoSurf 1) was used as the continuous phase. Highly monodisperse droplets of 151 µm in average diameter were produced and later polymerized by exposing to a long-wave UV light source (365 nm). We demonstrate that photocrosslinkable hydrogel droplets can be produced from HA-am. These microgels could enable the diffusion of nutrients and metabolites, while maintaining a size in which encapsulating sufficient cells to allow cell-cell interactions and proliferation would be possible. [1] J. A. Burdick and G. D. Prestwich, Adv. Mater., 2011, 23, 41–56. [2] H. Huang, Y. Yu, Y. Hu, X. He, O. Berk Usta and M. L. Yarmush, Lab Chip, 2017, 17, 1913–1932