Biomedical Engineering Reference
In-Depth Information
20
2.0
15
1.5
IRBC
1.0
10
0.5
5
Activated Platelet
0.0
0
0.0
0.5
1.0
1.5
2.0
Fast (µm)
FIGURE 15.3
AFM.images.of.one.gluteraldehyde-ixed.
Plasmodium
.
falciparum
.IRBC.initially.bound.under.low.conditions.on.
platelet-coated.surface.
After.smearing,.the.samples.should.be.immediately.moved.into.a.sealed.box.or.glass.jar.
containing.a.desiccant.such.as.anhydrous.silica..As.these.samples.have.not.been.ixed,.it.
is.vital.that.samples.are.always.transported.in.a.sealed.container.with.plenty.of.desiccant;.
otherwise,.water.droplets.condensing.on.the.erythrocytes.will.cause.cell.lysis.or.signii-
cant.membrane.damage.
In.certain.circumstances,.it.is.advantageous.to.ix.the.IRBCs.of.interest.prior.to.AFM.scan-
ning..For.example,.if.one.wishes.to.scan.
Plasmodium
IRBCs.that.have.bound.to.a.substrate.
coated.with.a.particular.receptor,.it.is.preferable.to.ix.the.adherent.cells.with.ixatives.to.
ensure.that.they.retain.their.shapes.in.situ.(Figure 15.3)..However,.when.ixing.IRBCs.with.
chemicals,.one.should.carefully.choose.the.proper.ixative.and.stick.to.the.optimized.ixing.
protocols.in.terms.of.ixing.time.and.ixative.concentration..We.have.found.that.1%.glutar-
aldehyde.in.phosphate-buffered.saline.(PBS).ixing.for.1.h.works.ine to.preserve.the.cells'.
surface.structures,.but.a.higher.concentration.and.overixing.induce.artiicial.excrescence.
structures. on. the. cell. surface.. Also,. methanol. and. formaldehyde/paraformadehyde. may.
not.work.as.well.as.glutaraldehyde.and.would.alter.the.cell.morphology.signiicantly.
After.the.sample.has.been.properly.prepared,.one.will.need.to.choose.a.suitable.scan-
ning.mode.to.image.the.sample.surface..The.commonly.used.contact.mode.and.tapping.
mode.in.air.are.both.able.to.reveal.the.surface.structures.at.fairly.high.resolution;.however,.
the.tapping.mode.is.preferred.since.the.lateral.scanning.force.is.signiicantly.reduced.in.
the.tapping.mode,.and.thus.minimizes.the.possibility.of.scanning-induced.distortion.or.
removal.of.the.cells..It.is.also.important.to.check.the.tip.geometry.and.sharpness.prior.to.
scanning.to.get.rid.of.any.possible.tip.shape-induced.artifacts,.such.as.dual.knobs.
15.6 TheNanotopographyofRedCellsInfectedwith
Plasmodium
spp.
As. previously. mentioned,.
Plasmodium
. spp.. cause. signiicant. changes. to. the. morphologi-
cal.and.biomechanical.properties.of.the.host.red.blood.cell..While.most.studies.focus.on.
laboratory. clones. of.
P. falciparum
,. it. is. important. to. realize. that. these. long-term. cultures.
