Biomedical Engineering Reference
In-Depth Information
peptide
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.have.been.successfully.used.to.enhance.the.cell.labeling.capacity.of.SPIO.nano-
particles..Arbab.and.co-workers.have.shown.long-term.(28-day).viability.for.mesenchymal.
and.hematopoietic.stem.cells.that.were.transfected.with.Feridex.as.the.SPIO.and.protamine.
sulfate,. a. cationic. transfection. agent.
223
. Zhang. et. al.. showed. that. the. transfection. agent.
Lipofectamine™.2000.with.SPIO.Endorm
®
.could.label.pig.skeletal.myoblasts.nearly.100%,.
whereas.the.mean.individual.cell.labeling.without.transfection.was.70%.
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2.17 SPIOApplicationsinCellTracking
Noninvasive,.high-resolution.MRI.is.poised.to.become.increasingly.used.in.the.character-
ization. and. evaluation. of. microstructure. and. function. in. tissue. engineering. and. regen-
erative. medicine.. The. spatial. MRI. resolution,. near-cellular. resolution. (30. mm),. and. use.
of. iron. oxide. contrast. agents. have. expanded. MRI's. ability. to. image. speciic. cells. at. the.
single-cell. level.. This. ability. in. single-cell. imaging. is. proposed. for. visualization. of. cell.
seeding.in.biological.or.synthetic.3D.scaffolds.and.has.great.potential.for.screening.dif-
ferent.cell.types.in.a.3D.scale,.whereas.light.microscopy.can.only.permit.2D.or.limited.3D.
imaging..Contrast.agents.are.another.strategy.to.enhance.resolution..SPIO.nanoparticles.
as.contrast.agents.are.special.for.cell.labeling,.as.they.can.be.loaded.on.cells.within.1.h.
225
.
Their.intracellular.concentration.(5-10.µmol/L).is.suficient.to.generate.detectable.signals.
on.T2-weighted.images.
226
Poirier-Quinot.et.al..showed.that.high-resolution.MRI.on.a.clinical.1.5.T.device.is.a.reli-
able. technique. to. assess. magnetically. labeled. mesenchymal. cell. seeding. on. 3D. porous.
scaffolds.before.and.after.in.vivo.implantation.
227
.They.detected.mesenchymal.stem.cells.
with.different.iron.loads.(5,.12,.and.31.pg.of.iron.per.cell).after.seeding.on.scaffolds,.using.
gradient-echo.MR.images.according.to.phase.distortions.and.areas.of.intensely.low.sig-
nal..In.vivo.monitoring.of.the.implanted.scaffolds,.tracking.of.the.seeding.cells,.and.the.
behavior.of.tissue.surrounding.the.implant.are.other.features.of.MRI..Ko.et.al..used.MRI.to.
monitor.the.cellular.behavior.around.the.implant.in.gel/sponge.scaffolds.that.were.seeded.
with.magnetically.labeled.mesenchymal.cells.and.correlated.their.results.to.histological.
data.
228
.Moreover,.MRI.can.be.used.to.monitor.the.cell.proliferation.in.other.3D.culturing.
equipment,.such.as.hollow.ibers,.where.visualizing.the.cells.is.the.main.limitation.
229
Endothelial.progenitor.cells.can.migrate.to.the.ischemic.site.under.angiogenic.site.tro-
pism,. and. studying. the. migration. mechanism. in. in. vitro. models. can. offer. a. promising.
therapeutic. alternative. to. the. angiogenic. growth. factors.. High-resolution. MRI. has. been.
used. successfully. to. follow. the. formation. of. vascular. type. networks. in. Matrigel.
230
. The.
main.limitation.of.MRI.in.single-cell.detection.is.that.the.current.high-resolution.systems,.
such. as. high-temperature. superconducting. cryo-detection. coils,. permit. high-resolution.
imaging.in.a.relatively.small.volume,.close.to.the.coil.surface.(<15.mm).and.cannot.be.used.
in.a.bigger.area.
Numerous. cell. types. have. been. investigated. using. superparamagnetic. nanoparticles.
in. experimental. disease. models,. including. central. nervous. system. diseases.. Endorem-
labeled. human. mesenchymal. stem. cells. were. grafted. either. intracerebrally. or. intrave-
nously. in. experimental. models. of. stroke.
231
. Using. a. 4.7. T. Bruker. spectrometer,. 1. week.
after.cell.transplantation,.a.hypointense.signal.was.found.in.the.lesion..The.signals.were.
intensiied. during. the. second. and. third. weeks. after. grafting,. regardless. of. the. route. of.
administration,.and.their.intensity.corresponded.to.the.Prussian.blue.staining,.anti-BrdU.
