Biomedical Engineering Reference
In-Depth Information
deformation.by.decompression..In.this.study,.a.thin.PDMS.membrane.was.placed.upon.an.
acrylic.plate.in.which.multiple.cavities.(1535.holes,.1.0.mm.in.diameter).had.been.gener-
ated. using. a. programmable. micromilling. system.. These. cavities. were. connected. with. a.
silicon.tube.to.decompress.the.spaces.between.the.membrane.and.the.cavities..Thus,.the.
PDMS.membrane.could.be.deformed.into.hemispherical.cavities..After.treating.the.PDMS.
membrane.with.Pluronic.(F-127).to.prevent.cell.adhesion,.cells.were.seeded.onto.the.mem-
brane.and.the.membrane.was.deformed.by.vacuum..After.5.days.of.culture,.the.pressure.
was.raised.from.vacuum.back.to.atmospheric.pressure,.and.the.spheroids.on.the.PDMS.
membrane.were.then.retrieved.from.the.culture.device.using.a.plastic.pipette..Using.this.
technique,.they.were.able.to.generate.spheroids.of.human.osteosarcoma.MG63.cells.and.
human.hepatoma.cell.line.HepG2..These.spheroids.could.presumably.be.used.for.a.variety.
of.applications.including.drug.screening.and.tissue.engineering.
Lee.et.al..(2008b).applied.microfabrication.techniques.to.generate.3D.culture.arrays.for.
toxicology.screening..In.this.study,.3D.cell-culture.microarrays.with.cells.immobilized.in.
20-60.nL.spots.of.cross-linked.alginate.were.generated.by.spotting.cell-alginate.mixtures.
onto.poly(styrene-
co
-maleic.anhydride).(PSMA)-treated.glass.slides.that.had.been.previ-
ously.spotted.with.a.40.nL.mixture.of.poly-l-lysine.(PLL).and.barium.chloride.(BaCl2).to.
promote.spot.adhesion.and.alginate.cross-linking..More.recently,.we.applied.this.technol-
ogy.to.high-throughput.screening.of.silencing.RNA.with.an.objective.of.identifying.target.
for.cellular.engineering.for.bioprocessing.(Zhang.et.al..2012).
15.3.3.3 Cell-Culture Substrates
A.variety.of.nanopatterned.and.nanostructured.materials.have.been.used.for.mammalian.
cell.culture.dating.back.for.over.a.decade.(Craighead.et.al..2001)..A.number.of.recent.stud-
ies.have.explored.the.use.of.nanoscale.materials.for.the.culture.of.a.number.of.cell.types,.
including. CHO. cells.. While. it. is. not. clear. that. these. culture. techniques. will. have. direct.
applicability.in.bioprocessing,.one.could.envision.that.they.might.be.used.for.cell.screening.
studies.or.media.optimization..Agrawal.et.al..(2010).recently.described.the.use.of.porous.
nanocrystalline.(pnc).silicon.membranes.for.cell.culture..These.membranes,.at.15.nm.thick,.
approximately. 1000. times. thinner. than. any. polymeric. membrane,. exhibit. permeability.
to. small. solutes. that. is. orders. of. magnitude. greater. than. conventional. membranes.. The.
pnc-silicon.membranes.were.quite.biocompatible,.showing.comparable.results.to.cultures.
performed.on.polystyrene.and.glass..The.pnc-silicon.membranes.also.dissolved.in.cell.cul-
ture.media.over.several.days.without.cytotoxic.effects..CHO.cells.were.recently.cultured.
on.two.types.of.uncoated.chemical.vapor-deposited.thin.nano-.and.microcrystalline.dia-
mond. surfaces,. hydrophobic. hydrogen. and. hydrophilic. oxygen-terminated. (Smisdom. et.
al..2009)..Frequently,.in.order.to.obtain.better.cell.survival,.diamond.surfaces.are.coated.
with.laminin,.collagen,.or.poly-d.or.l-lysine;.however,.there.are.advantages.to.growing.the.
cells.on.bare.surfaces..In.this.study,.optical.and.biochemical.analyses.show.that.compared.
to.glass.controls,.growth.and.viability.were.not.signiicantly.altered,.and.neither.grain.size.
nor.surface.termination.had.a.signiicant.inluence.until.5.days.post-seeding.
Other.recent.studies.have.examined.the.effects.of.alignment.and.nanoscale.structures.
on.the.growth.of.CHO.cells..Peterbauer.et.al..(2010).employed.polystyrene.ilms.with.peri-
odic.surface.ripple.structures.generated.by.laser.processing.to.investigate.the.dynamics.of.
cell.alignment.and.attempt.to.gain.insight.into.the.nature.of.the.cell-speciic.component(s).
responsible.for.the.observed.differences.in.cell.behavior..As.expected,.cells.were.oriented.
by. the. grooves;. in. addition,. differences. in. morphology. were. also. observed.. CHO. cells.
showed.a.circularity.of.0.43.±.0.19.on.the.patterned.surface,.signiicantly.lower.compared.
