ENGINEERING 2D AND 3D CELLULAR MICROENVIRONMENTS USING LASER DIRECT WRITE - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 119

FIGURE 5.7
Microcapsules created by processing microbeads fabricated and patterned by LDW. (a) Human breast cancer cells in
poly-L-lysine capsules after 7 days, and (b) mouse embryonic stem cells in chitosan capsules after 3 days, illustrate
that the hollow microcapsules allow cell growth over time within a constrained geometry. The breast cancer cells
grow to fill the hollow capsule, and the stem cells form an embryoid body (EB) contained with the microcapsule.
The many differences between these images illustrate that the material, cell type, and other features of the
microenvironment can greatly influence cell behavior. Scale bars are 500 m m.
5.5 CONCLUSIONS AND FUTURE DIRECTIONS
There are some aspects of cellular behavior, such as migration, differentiation, and certain types
of gene expression, that are heavily influenced by the cellular microenvironment. Both mechanical
signals from the substrate and biochemical signals, either soluble or insoluble, have profound ef-
fects on cell fate and function, and are being widely studied. However, cell-cell signaling is also an
important influential factor in cell behavior, yet this is rarely studied, due, in part, to the complexity
and technical challenges in doing so. Therefore, it may be prudent to control how cells signal within
the microenvironment. Factors that can be manipulated include whether the cellular signaling is
homotypic or heterotypic, the strength of the signal based on the number/density and placement of
cells, and the signaling dynamics. Herein, we have discussed patterning approaches, in particular
LDW, to control cell placement in engineered microenvironments. Although it is all but impossible
to mimic the sheer complexity of multiple cell types and signals in vivo , spatially precise patterning
approaches onto engineered substrates offers a powerful tool to prescribe and control cellular signaling
for in vitro experiments.
LDW has been used to print multiple types of cells in custom patterns, which allows the fabrication
of microenvironments that can maximize (or minimize) a desired behavior based solely on cellular
arrangement. Micropatterning has been used to show that cell size/shape or colony size can influence
cell fates, but it generally does not allow evolution of structure. Moreover, the adhesive proteins that
are patterned confound cell signaling, making it difficult to decouple the effect of the adhesive protein
and the effect of cellular signaling.