ENGINEERING 2D AND 3D CELLULAR MICROENVIRONMENTS USING LASER DIRECT WRITE - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 114

FIGURE 5.5
Examples of cells printed by LDW, and evolution of structure over time. Array of human dermal fibroblasts
(a) immediately after printing and (b) 24 h after printing, showing the evolution of cellular network structure
from the initial printing positions. Contrast is adjusted to show detail. Lines of mouse embryonic stem cells
(c) immediately after printing and (d) 48 h after printing, demonstrating the formation of embryoid bodies (EBs) on
an unrestricted uniform substrate due to collective cellular behavior, rather than constrained growth. Bubbles in the
background are artifacts of securing the substrate. Scale bars are 500 m m.
micropatterning approach previously used to study this phenomenon only allows the combined effect
of the patterned protein and colony size to be studied. However, it would be ideal to study the effect of
colony size and the surface-coated protein independently.
Controlling EB size can potentially be very useful to direct differentiation, and LDW has been
used to control EB size, via the density of printed cells, independent of the stem cell colony di-
ameter ( Dias et al., 2014 ). While colony size did not influence the size of the EBs that formed, the
effect of colony size on stem cell differentiation based on cellular patterning on a homogeneous
substrate still needs to be determined. Prescribing these factors in engineered microenvironments
could allow more efficient directed differentiation of stem cells. Additionally, differentiation can
also be influenced by printing protein gradients, as reviewed ( Tasoglu et al., 2013 ). The versatil-
ity afforded by LDW for printing cells, biomaterials, and proteins, enables complex studies to
differentiate stem cells, influence migration, and answer many other questions using engineered
microenvironments.