Biomedical Engineering Reference
In-Depth Information
types. A path of IKVAV peptides (the cell-attachment peptides of laminin) was “built” irst by
photo-cross-linking a path of biotinylated BSA, then by exposing the gel to avidin, and inally by
exposing the gel to biotinylated IKVAV peptides, which attached selectively to the photo-cross-
linked BSA path. It was demonstrated that DRG neurons and hippocampal neural progenitor
cells selectively grew and migrated on the IKVAV 3-D paths (
Figure 7.3d
).
Laser writing is not widely accessible to biology laboratories and only works with very
speciic photochemical groups (which may require specialized chemical synthesis not
available in most biological laboratories); so many groups have pursued diferent ways of
building 3-D microscafolds for tissue engineering. In 1998, Linda Griith's group at the
Massachusetts Institute of Technology (MIT) printed biodegradable polymer scafolds using
a solid free-form printing process. he microscafolds were polymerized layer by layer using
biodegradable polylactic acid [modiied with
poly(ethylene-oxide)
-poly(propylene-oxide)
copolymers] and cell-adhesive carbohydrate ligands (speciic for the hepatocyte asialogly-
coprotein receptor) to promote hepatocyte attachment. he technique has the potential for
creating low-resolution scafolds in which each point can be tailored at will as adhesive or
nonadhesive to cells.
Local-phase
microgels
Encapsulated:
Microbeads
Protein
Cells
single,
random,
3D patterned
a
Bulk-phase
polymer
ag
f
BMEL
alg
b
c
ITO-coated glass
V
Side view
Micropatterned dielectric
500 µm
1% Agarose
Top view
Exposed ITO
Light/
temp.
2% calcium
alginate gel
100 µm
d
Multiphase
DEP-patterned
tissue construct
Live
/
dead
e
Bulk-phase hydrogel
Cells embedded in
local-phase hydrogel
100 µm
FIGURE 7.4
Fabrication.of.micropatterned.tissue.constructs.by.multiphase.dielectrophoresis..(From.
Dirk. R.. Albrecht,. Gregory. H.. Underhill,. Avital. Mendelson,. and. Sangeeta. N.. Bhatia,. “Multiphase.
electropatterning.of.cells.and.biomaterials,”.
Lab Chip
,.7,.702-709,.2007..Reproduced.with.permis-
sion.from.The.Royal.Society.of.Chemistry.)
