Biomedical Engineering Reference
In-Depth Information
optics,. and. mechanical. stages. while. simply. switching. out. print. ribbons. promises. great.
utility.as.a.tool.for.both.biological.studies.and.tissue.engineering.
13.4.3  Printing Mammalian Cells
The. ability. to. print. cells. in. a. precise. 2D. and. layer-by-layer. manner. is. critical. for. the.
future. of. tissue. engineering.. Using. current. homogeneous. scaffold. seeding. methods.
it. is. dificult. to. produce. functional. tissue.. This. is. because. all. complex. tissue. constructs.
rely.on.heterogeneous.structure.such.as.vasculature..Laser.direct-write.offers.the.ability.
to. print. different. cell. groups. to. selected. areas,. and. even. the. ability. to. do. this. in. three.
dimensions..AFA-LIFT.with.a.silver.ilm.50.nm.thick.as.the.absorbing.ilm.has.been.used.
to.print.fungi,. Trichoderma longibrachiatum ..Transfer.of.the.fungi.was.achieved.at.ambient.
conditions. without. the. contamination. of. silver. particles,. as. detected. via. microscopy..
The.lack.of.cotransfer.of.silver.particles.would.have.otherwise.discounted.the.AFA-LIFT.
method.for.fear.of.contamination.on.the.receiving.substrate..While.the.fungi.cells.suffered.
accelerations.on.the.order.of.10 9 .g,.they.survived.and.maintained.reproductive.capability.
after.the.transfer..Further.studies.showed.that.fungi.transferred.by.an.AFA-LIFT.process.
survived.at.a.rate.of.75%.at.the.best.transfer.pulse.luence.of.355.mJ/cm 3 .(Hopp.et.al..2004).
Transfer.of.MG.63.osteoblast-like.cells.was.conducted.using.a.MAPLE.DW.technique,.
demonstrating.near.100%.posttransfer.viability,.as.well.as.no.morphological.alterations.to.
the.cells.when.compared.to.control.cell.growth.in.culture.conditions..Transfers.of.a.MG.
63/hydroxyapatite. composite. were. also. demonstrated,. and. growth. proiles. of. both. the.
cells.and.cells.in.composite.were.virtually.identical.with.control.cells.(Doraiswamy.et.al..
2006)..Osteosarcoma.MG.63.cells.have.also.been.printed.onto.electrospun.polycaprolactone.
(PCL).nanoibrous.matrices.of.100.μm.thickness.as.a.receiving.substrate..Printing.onto.a.
single.sheet.revealed.a.positive.live-dead.assay,.as.well.as.growth.of.extracellular.matrix.
between. the. PCL. ibers.. Use. of. thin. sheets. as. receiving. substrates. allowed. for. layer-by-
layer.construction.of.3D.patterns..Cells.were.seen.to.maintain.spatial.coniguration.when.
viewed. after. 4. days,. although. proliferation. eventually. blurred. printed. patterns. (Catros.
et. al.. 2011).. B35. neuronal. cells. have. been. printed. onto. a. Matrigel. (a. commonly. used.
gelatinous.protein.mixture.for.cell.culture).receiving.substrate.using.MAPLE.DW..Only.
3%. of. cells. were. found. to. have. undergone. apoptosis. due. to. damage. from. transfer.. No.
signiicant. difference. was. seen. between. axonal. projection. growth. and. cell. proliferation.
between. the. printed. cells. and. control. cultures. after. 72.h.. It. was. also. demonstrated. that.
cells. could. be. made. to. penetrate. into. the. receiving. Matrigel. substrates,. with. the. depth.
of. penetration. being. dependent. on. the. viscosity. of. the. substrate.. Additionally,. raising.
or.lowering.the.laser.luence.used.affects.the.penetration.depth.via.altering.the.transfer.
velocity,. and. thus. alters. the. impact. properties. as. described. in. earlier. sections.. This.
was. used. to. transfer. B35. cells. to. multiple. depths.. Cells. transferred. to. deeper. into. the.
Matrigel.showed.axonal.extension.similar.to.that.seen.on.the.Matrigel.surface,.and.axonal.
processes. were. also. formed. between. cell. layers. (Patz. et. al.. 2005).. In. addition,. cells. can.
also.be.immobilized.between.layers.of.hydrogel.after.printing..The.usefulness.of.using.an.
electrospun.polymer.layer.lies.in.its.better.mechanical.properties,.which.allow.for.easier.
handling,.allowing.relative.ease.in.layering.to.create.multi-layered.structures..As.with.any.
tissue-engineered.construct.with.thickness.greater.than.100.μm,.nutrient.distribution.will.
have. to. be. addressed.. However,. these. techniques. for. 3D. printing. offer. a. glimpse. at. the.
potential.of.the.laser.direct-write.system.
Cellularized. cardiac. patches. have. been. prepared. with. the. LIFT. technique.. They. were.
patterned.with.human.umbilical.vein.endothelial.cells.(HUVEC).and.human.mesenchymal.
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