Session: PMSE/POLY Poster Session:

Culturing cancer cells in a three-dimensional (3D) environment better recapitulates in vivo conditions including cell-to-cell interactions and mass transfer limitations of metabolites, oxygen, and drugs. Existing approaches for 3D cell culture can rapidly generate a large number of spheroids; however, they suffer from significant heterogeneity since they are generated from hundreds to thousands of different cells. Droplet microfluidic devices offer a promising alternative to grow 3D spheroids from a small number (~10) of cancer cells to reduce cellular heterogeneity. The goal was to incorporate a novel thiol-acrylate (TA) hydrogel scaffold into a microfluidic droplet trapping array to generate and study 3D spheroids. The TA hydrogel was synthesized using two readily available thiol (ETTMP 1300) and acrylate (PEGDA 700) monomers polymerized by a base-catalyzed Michael addition reaction. The resultant hydrogel was biodegradable and previously demonstrated to severe as an excellent scaffold for 3D cell culture. Two different trapping arrays were fabricated with 150 or 300 µm diameter traps to investigate the effect of droplet size and cell seeding density on spheroid formation and growth using the TA hydrogel scaffold. The 150 and 300 µm trapping arrays were capable of ~99% droplet trapping and ~90% cellular encapsulation. The TA hydrogel allowed for rapid (~30-40 min) polymerization of the scaffold followed by removal of the oil phase and replacement with complete media to initiate long-term spheroid culturing. The growth and viability of model breast cancer spheroids using MCF7 at 37°C were confirmed for up to seven days under continuous media flow using a customized gravity-driven system to eliminate the need for expensive external syringe pumps. This study identified that a minimum of 10 encapsulated cells is needed to generate a spheroid and that droplets starting with >10 cells are unlikely to form into viable spheroids. The findings from this study highlight an alternative approach to generate 3D spheroids incorporating an easy-to-use, inexpensive scaffold that can be used for high-throughput drug screening.

James Dorman

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