Enzymatic outside-in cross-linking enables single-step microcapsule production for high-throughput three-dimensional cell microaggregate formation

• Main Authors: B. van Loo, S.S. Salehi, S. Henke, A. Shamloo, T. Kamperman, M. Karperien, J. Leijten
• Format: Article
• Language: English
• Published: Elsevier 2020-03-01
• Series: Materials Today Bio
• Subjects: Cell encapsulation; Droplet microfluidics; Enzymatic cross-linking; Hydrogel; Hollow microgel; Cell spheroid
• Online Access: http://www.sciencedirect.com/science/article/pii/S2590006420300077

Cell-laden hydrogel microcapsules enable the high-throughput production of cell aggregates, which are relevant for three-dimensional tissue engineering and drug screening applications. However, current microcapsule production strategies are limited by their throughput, multistep protocols, and limited amount of compatible biomaterials. We here present a single-step process for the controlled microfluidic production of single-core microcapsules using enzymatic outside-in cross-linking of tyramine-conjugated polymers. It was hypothesized that a physically, instead of the conventionally explored biochemically, controlled enzymatic cross-linking process would improve the reproducibility, operational window, and throughput of shell formation. Droplets were flown through a silicone delay line, which allowed for highly controlled diffusion of the enzymatic cross-linking initiator. The microcapsules' cross-linking density and shell thickness is strictly depended on the droplet's retention time in the delay line, which is predictably controlled by flow rate. The here presented hydrogel cross-linking method allows for facile and cytocompatible production of cell-laden microcapsules compatible with the formation and biorthogonal isolation of long-term viable cellular spheroids for tissue engineering and drug screening applications.