Microfluidics‐Assisted Fabrication of Microtissues with Tunable Physical Properties for Developing an In Vitro Multiplex Tissue Model

Abstract

Herein, a new 3D hydrogel‐based co‐culture tissue model is developed to systematically examine the effect of mutual influence between two different cell types residing in separated but interactive zones. Microtissues containing macrophage as a model cell type are first developed by photo‐crosslinking cell‐laden droplets containing methacrylic gelatin (MGel), using a microfluidic flow‐focusing device. Regardless of the material conditions, the cell viability is well maintained, demonstrating the biocompatibility of the fabrication process as well as the 3D microenvironment provided by the microgels. More significantly, it is shown that the proliferation and lipopolysaccharide (LPS)‐induced differentiation (Mφ polarization) of macrophages are heavily influenced by the mechanical properties of the microgels, controlled with MGel concentrations. Eventually, these macrophage microtissues are embedded into a larger tissue construct, containing either normal or cancer cells, to develop a co‐culture tissue model to study the mutual effects between macrophages in different stages of differentiation and the surrounding cells. It is expected that this “multiplex” tissue model would allow an effective platform for monitoring of complex interactions between two different cell types residing in adjacent, compartmentalized areas within a 3D tissue environment.

Complex Tuning of Physical Properties of Hyperbranched Polyglycerol‐Based Bioink for Microfabrication of Cell‐Laden Hydrogels

“…The monomers used for this study were PEGMA ( M n 500, Sigma Aldrich), acrylamide (Sigma Aldrich), and MGel. The detailed synthesis and characterization of MGel are provided in the Supporting Information (see Figure S9, Supporting Information) . For PEGMA and acrylamide, their concentrations were either 10 or 20%, while varying the AHPG concentration from 1 to 5%.…”

“…The proliferation rate ( k P ) of encapsulated cells was calculated by counting the number of live cells at various times, and fitting the plot of normalized number of viable cells ( N t / N 0 ) with time ( t ) with the following power‐law equation N t was the number of live cells at time, t , and N 0 was the initial number of live cells measured right after gelation ( t = 0). Two cell types, MCF‐7 (human breast adenocarcinoma cells) and D1 (murine mesenchymal stem cells) purchased from ATCC, were used for this study …”

Biopolymer-Based Microcarriers for Three-Dimensional Cell Culture and Engineered Tissue Formation

“…Microfluidics is a versatile method to obtain intricate microparticles with varying size and shape by producing emulsion droplets in microscale [58][59][60][61]. Monodisperse droplets can be efficiently developed and further engineered to generate microgels, which provides a valuable platform for 3D cell culture and miniaturized tissue engineering [62][63][64][65][66]. Lee et al [65] fabricated macrophage-laden microgels containing methacrylic gelatin for microtissue fabrication using a double flow-focusing microfluidic approach.…”

“…Monodisperse droplets can be efficiently developed and further engineered to generate microgels, which provides a valuable platform for 3D cell culture and miniaturized tissue engineering [62][63][64][65][66]. Lee et al [65] fabricated macrophage-laden microgels containing methacrylic gelatin for microtissue fabrication using a double flow-focusing microfluidic approach. Briefly, monodisperse droplets of gel precursor solution infused with cells were first generated by a microfluidic device having a flow-focusing geometry, followed by photo-crosslinking to generate cell-laden microgels (Figure 1).…”

“…The cells showed a more spread morphology when the microgels were softer, while cells with a more elongated morphology were observed when stiffer matrix was used for the microgels. Photo-crosslinked microgels with varying mechanical properties were also obtained from methacrylic gelatin for use as a 3D cell culture platform [65].…”