ENGINEERING 2D AND 3D CELLULAR MICROENVIRONMENTS USING LASER DIRECT WRITE - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 108

FIGURE 5.3
Materials utilized in LDW. The laser first interacts with a thin sacrificial layer, which can be either a hydrogel,
or a dynamic release layer (DRL), such as triazene, metals, or metal oxides. The biologic payload is typically
suspended in a transfer layer (e.g. glycerol for printing nucleic acids or proteins, hydrogel, or media for printing
live cells). When printing live cells, the cells can either be attached to the material to be transferred (e.g. when using
Matrigel ® ), or suspended in hydrogel or media in their trypisinized state. The receiving substrate typically utilizes a
thin hydrogel coating as well, to provide viscous dissipation of energy.
variability may be a source of inconsistencies among researchers, and can make it difficult to reproduce
previous findings. Further, not all Matrigel ® components are defined, and some concentrations are un-
known. Without knowing Matrigel ® 's exact content and concentration of proteases, growth factors, and
other proteins, the amount of information that may be inferred from an experiment is largely limited. In
an experiment using Matrigel ® , it is impossible to know what factor or factor combination is respon-
sible for the observed cellular behavior, since any potential influence by Matrigel ® 's numerous unspeci-
fied constituents cannot be ruled out. Although Matrigel ® provides a cost-effective basement membrane
substitute because it is derived from mouse sarcoma cells, it could elicit an extreme immune response
if implanted into the body. Moreover, extrapolating cell behavior observed on a mouse tumor extract to
a human condition could be inaccurate.
5.2.3 GELATIN-BASED LDW
Among the hydrogel materials explored for use with LDW, gelatin has proven quite promising. Gela-
tin is a natural polymer that is a reduced and degraded form of collagen. At room temperature, gelatin
is a stiff gel, but at incubation temperatures (37°C), the polymer network becomes soluble. In LDW