Biomedical Engineering Reference
In-Depth Information
(a)
Phase contrast
Live/dead
(b)
(c)
FIGURE 12.7
Individual. cell-laden. microgels. are. irst. patterned. by. crosslinking. with. a. photomask,. and. then. the. second.
crosslinking. can. lock. up. the. self-assembled. microgels. (a).. Surface. tension. drives. microgels. to. minimize. the.
exposed. surfaces. to. hydrophobic. luid,. leading. to. self. assembly. according. to. shapes. (b). and. (c).. (Scale. bars,.
100.μm.).Stained.cells.encapsulated.in.microgels.can.be.assembled.to.implement.designed.structures..Adapted.
with.permission.from.reference.95..Copyright.2008.National.Academy.of.Sciences,.U.S.A.
hydrogel. prepolymer. solution. is. mixed. homogeneously. with. cell. suspension. and. gelled.
rapidly.to.construct.3D.structures..Among.available.polymers,.PEG-based.hydrogels.have.
been. used. widely. because. of. its. biocompatibility. and. photo. patternability. to. generate.
customized. pattern. shapes.. PEG. has. been. proven. to. be. useful. in. biomedicine. ield. due.
to. its. ability. to. prolong. the. circulating. time. of. drugs. in. vivo.
92-93
. PEG. does. not. initiate.
cytotoxicity. and. immunogenicity. and. is. FDA. approved. for. speciic. applications.. Tsang.
and.colleagues.developed.a.method.to.pattern.cell-laden.hydrogels.layer.by.layer,.which.
can. be. used. to. construct. a. hepatocyte. tissue.
94
. Hepatic. functions. including. cumulative.
albumin.secretion.and.urea.synthesis.increased.100%-260%.rather.than.unperfused.plug.
with.same.cell.density..Khademhosseini.and.co-workers.combined.self-assembly.technique.
with. photopatterned. PEG. building. blocks. to. provide. a. highly. scalable. approach. for. the.
formation. of. 3D. cell. microenvironments. (Figures. 12.7).
95
. They. employed. shape. directed.
self-assembly.to.increase.the.possibility.of.desired.assembly.between.two.different.types.
of.microgels..Dielectrophoretic.(DEP).forces.can.localize.single.cells.within.a.luid;.thus.
live.cells.suspended.in.prepolymer.solution.were.photoimmobilzed.after.relocation.of.cells.
using.this.electropatterning.method.
64
.Compared.with.other.methods.with.homogeneously.
dispersed.cells.inside.PEG.solutions,.the.proposed.way.in.this.research.can.control.cell-
cell.interactions.within.a.small.environment..Even.though.PEG.based.hydrogels.provide.
an.easy.method.to.construct.3D.cell.ECM.structures,.other.types.of.hydrogels.are.being.
