Biomedical Engineering Reference
In-Depth Information
hematopoietic. stem. cells. (BM-HSCs).. Augmenting. topographical. cues. with. biochemical.
ones.stimulated.fast.and.higher-number.BM-HSC.adhesion.to.the.substrate.(Ma.et.al..2008)..
In.another.study,.pre-osteoblastic.cells.cultured.on.poly(l-lactide-
co
-ε-caprolactone).(PLCL).
meshes.containing.immobilized.Arg-Gly-Asp.(RGD).peptide.(a.common.adhesive.ligand.
of. ECM. proteins). exhibited. better. cell. adhesion. and. proliferation. capacities. than. PLCL.
meshes.sans.surface.modiication..Additionally,.improvement.in.differentiation.potential.
was.also.observed,.with.more.calcium.deposits.and.higher.osteogenic.gene.expression.by.
cells. on. the. PLGA. surfaces. possessing. the. RGD. peptide. (Shin. et. al.. 2010).. These. results.
highlight. that. biochemical. cues. can. act. in. concert. with. topographical. cues. to. elicit. the.
desired.cell.behavior.on.electrospun.ibrous.scaffolds.
8.2.1.2 Thermally Induced Phase Separation
Thermally.induced.phase.separation.(TIPS).generally.consists.of.the.following.procedures:.
polymer. dissolution,. phase. separation. and. gelation,. solvent. extraction,. freezing,. and.
freeze. drying. (Holzwarth. and. Ma. 2011).. When. subject. to. certain. temperatures,. the.
polymer. solution. partitions. into. a. polymer-rich. phase. and. a. polymer-poor. phase.. The.
polymer-rich. fraction. eventually. hardens,. while. the. polymer-poor. fraction. is. extracted.
(Figure. 8.2b).. Gelation. is. regarded. as. the. crucial. step. for. dictating. the. scaffold's. porous.
morphology. (Smith. and. Ma. 2004).. By. modifying. various. thermodynamic. and. kinetic.
parameters,. different. porous. architectures. can. be. easily. obtained. (Nam. and. Park. 1999)..
Combining. TIPS. with. other. scaffold-generating. techniques. opens. up. the. possibility. for.
further.manipulation.of.pore.size.and.shape.
To. artiicially. replicate. the. physical. and. chemical. nature. of. collagen,. a. nanoibrous.
gelatin.scaffold.was.generated.via.TIPS.and.subsequently.leached.with.parafin.to.produce.
spherical.pores..Preliminary.studies.indicated.that.this.3D.scaffold.could.retain.its.shape.
after. culture. with. osteoblasts;. conversely,. constructs. using. commercially. purchased.
scaffold.material.Gelfoam
®
.experienced.a.decrease.in.size.(Liu.and.Ma.2009).
Although. TIPS-produced. structures. in. the. nanoscale. range. remain. sparse,. those. on.
the. microscale. level. remain. an. attractive. option. whereby. to. observe. cell. behavior.. On.
polyurethane. TIPS. scaffolds,. seeded. embryonic. stem. cell. (ESC)-derived. cardiomyocytes.
exhibited. a. rounded. morphology;. although. not. well-understood,. this. was. speculated. to.
be.the.result.of.an.early.differentiation.time.point.because.there.was.little.cell.iniltration.
into.the.scaffold..Cell.viability.was.also.less.than.that.of.polyurethane.electrospun.ibers..
However,. most. notably,. contractile. activity. could. be. detected. on. both. types. of. scaffolds.
(Fromstein. et. al.. 2008).. In. another. study,. human. bone-marrow. stromal. cells. seeded. on.
3D. terpolyester. of. 3-hydroxybutyrate,. 3-hydroxyvalerate,. and. 3-hydroxyhexanoate.
(PHBVHHx).scaffolds.showed.that.proliferative.capacity.increased.with.pore.size,.while.
differentiation.to.a.neural.phenotype.relied.on.the.converse.(Wang.et.al..2010)..Improved.
cell. seeding. was. observed. in. poly(l-lactide). (PLLA). scaffolds. incorporating. ibrin. gel.
within. their. pores,. with. chondrocytes. experiencing. more. uniform. distribution. and.
maintaining. their. round. morphology.. Furthermore,. cell. viability. and. proliferation. were.
enhanced.signiicantly..Chondrocyte.growth.rate.became.more.rapid,.along.with.greater.
ECM.production.(Zhao.et.al..2009).
8.2.1.3 Self-Assembly
Molecular. self-assembly. entails. the. spontaneous. aggregation. of. molecules. into. an.
organized.and.stable.form.(Whitesides.et.al..1991)..The.combined.effect.of.various.weak,.
