Elsevier

Biomaterials

Volume 32, Issue 6, February 2011, Pages 1477-1483
Biomaterials

High-throughput generation of hydrogel microbeads with varying elasticity for cell encapsulation

https://doi.org/10.1016/j.biomaterials.2010.10.033Get rights and content

Abstract

Elasticity of cellular microenvironments strongly influences cell motility, phagocytosis, growth and differentiation. Currently, the relationship between the cell behaviour and matrix stiffness is being studied for cells seeded on planar substrates, however in three-dimensional (3D) microenvironments cells may experience mechanical signalling that is distinct from that on a two-dimensional matrix. We report a microfluidic approach for high-throughput generation of 3D microenvironments with different elasticity for studies of cell fate. The generation of agarose microgels with different elastic moduli was achieved by (i) introducing into a microfluidic droplet generator two streams of agarose solutions, one with a high concentration of agarose and the other one with a low concentration of agarose, at varying relative volumetric flow rate ratios of the two streams, and (ii) on-chip gelation of the precursor droplets. At 37 °C, the method enabled a ∼35-fold variation of the shear elastic modulus of the agarose gels. The application of the method was demonstrated by encapsulating two mouse embryonic stem cell lines within the agarose microgels. This work establishes a foundation for the high-throughput generation of combinatorial microenvironments with different mechanical properties for cell studies.

Section snippets

Materials

Agarose with a gelling temperature in the range of 18–26 °C (ultra-low gelling temperature agarose) was purchased from SeaPrep (Lonza, Switzerland, www.lonza.com). Phosphate buffer solution (1 wt.%) was purchased from Gibco-BRL (Rockville, MD). A non-ionic surfactant Span-80, mineral oil and glycerol were supplied by Aldridge-Sigma Canada. A 3 wt.% agarose solution was prepared by dissolving 1.5 g of agarose in 48.5 g of a 1 wt.% PBS solution under heating to 70 °C, and subsequent cooling to

Results and discussion

To develop a method for MF generation of libraries of hydrogel microenvironments with different mechanical properties for cell studies we used the following considerations.

  • (i)

    The concentrations of agarose in the concentrated and dilute solutions (supplied as Streams 1 and 2, respectively) had to be such that sufficient mixing occurred in the serpentine channel and controlled emulsification took place in the MF droplet generator with a geometry shown in Fig. 1;

  • (ii)

    The lower limit of Cag in the

Conclusions

We have demonstrated an MF method for the continuous, fast, high-throughput generation of agarose-based 3D cellular microenvironments with precisely controlled dimensions and varying mechanical properties. The method paves the way for efficient studies of the effect of microenvironment elasticity on the behaviour of cells, which, after incubation within agarose microgels, can be analyzed by optical microscopy and flow cytometry. The method can be extended to the generation of combinatorial of

Acknowledgements

The authors thank Canada Research Chair Grant (NSERC Canada) and Canadian Institutes for Health Research (CHIR) for financial support of this work. AK thanks NSERC Canada for NSERC-USRA scholarship. The authors acknowledge assistance in experimental work by Ms. Lsan Tzadu.

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