Biomedical Engineering Reference
In-Depth Information
FIGURE 5.4
RFP normal human lung fibroblasts printed by LDW onto PLLA electrospun nanofiber substrates. Nanofibers
are aligned on the substrate, oriented left-to-right in images. Fibroblasts (a-b) immediately after printing appear
rounded in their trypsinized state, but (c-d) after one day begin to align in the direction of the electrospun fibers.
Scale bars are 200
m
m.
Various methods for laser-based deposition have been utilized, each quite similar, but with some dis-
tinct (although often subtle) differences. In this chapter, we will group all of these methods under
“LDW,” although there are different preferences in the field about the most appropriate term to use.
LDW-based methods operate on the same general principle, illustrated in
Figure 5.2
. The major differ-
ence among the various LDW methods is their choice of energy-absorbing layers that can be used to
amplify laser energy.
The purpose of using a sacrificial material is so that biologics or cells are not themselves sacrificed
during a deposition event. Laser-induced forward transfer (LIFT) typically uses a metal or foil as a sac-
rificial layer, while matrix-assisted pulsed laser evaporation direct-write (MAPLE-DW) typically uses
a biologic matrix, such as Matrigel
®
or gelatin. Both methods have shown success depositing multiple
mammalian cell types in controlled patterns (
Table 5.2
). Moreover, custom configurations of cells, such
as grids, lines, and sheets have been demonstrated, with unrestricted cell growth from the initial printed
pattern (
Figure 5.5
).
Because the substrate is generally homogeneous, following LDW, cells are free to migrate, cluster,
or form structures uninhibited by geometric or biochemical restrictions on the substrate. This property of
LDW allows cellular migration and migration-based behavior to be studied. By observing structural evo-
lution, LDW enables different types of studies than what can be explored using micropatterned proteins,
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