Biomedical Engineering Reference
In-Depth Information
protein-protein.interactions.for.ilamentous.and.globular.proteins.and.the.coniguration.
of. protein. oligomers. have. been. captured. with. AFM. in. air. (Chen. and. Hansma. 2000). as.
well.as.in.luid.(Mou.et.al..1996;.Agarwal.et.al..2002,.2007;.Müller.et.al..2002)..Figure.16.2B.
exempliies.single-molecule.binding.events.in.an.aqueous.medium,.including.quantitative.
analysis.showing.particle.sizes.and.the.number.and.position.of.binding.events.(Agarwal.
et.al..2002)..Reviews.covering.a.diverse.range.of.AFM.applications.for.observing.the.struc-
tures.of.nucleic.acids.(Lyubchenko.et.al..2011),.proteins.(Müller.2008;.Baclayon.et.al..2010),.
and.nanoparticles.(Scalf.and.West.2006).can.be.found.in.the.literature.
Analysis.of.AFM.images,.such.as.those.produced.for.the.samples.described.earlier,.can.
provide.quantitative.information.such.as.the.lateral.width,.length,.height,.and.size.distri-
butions.of.single.molecules..The.number.and.position.of.protein.binding.events.and.their.
oligomerization.stoichiometry.can.also.be.determined.with.AFM..It.should.be.noted.that.
lateral.nanoscale.dimensions.of.a.sample.in.AFM.images.can.be.altered.by.the.size.and.
shape.of.the.probe.and.also.the.image.acquisition.parameters..However,.several.computer-
ized.algorithms.and.software.are.readily.available.to.account.for.and.correct.these.effects.
16.3.2 Cell and Tissue imaging
The.AFM.has.played.an.important.role.in.studies.of.cellular.and.tissue.surface.ultrastruc-
tures,.and.in.providing.insight.into.uptake.of.substances.or.nanoparticles.by.cells..Since.
the.AFM.enables.imaging.in.a.luid.environment.and.at.ambient.temperatures,.it.can.pro-
vide.very-high-resolution. images.of.cell.and.tissue.surfaces.without.the.need.for.ixing,.
staining,.or.sectioning.the.sample..We.highlight.later.a.few.key.AFM.studies.on.this.topic..
Comprehensive. reviews. of. the. advancements. in. cell. and. tissue. imaging. with. AFM. can.
also.be.found.in.the.following.review.articles.(Müller.2008;.Francis.et.al..2010).
AFM.imaging.has.aided.in.elucidating.many.behavioral.properties.of.cells..For.instance,.
Oberleithner.et.al..(2009).recently.used.AFM.to.demonstrate.how.the.addition.of.potassium.
to.the.culture.medium.stimulated.swelling.and.softening.of.live.vascular.endothelial.cells..
In.another.study,.AFM.topographs.showed.that.the.addition.of.a.drug.signiicantly.altered.
the.membrane.structure.of.a.bacterial.cell.(Francius.et.al..2008),.resulting.in.cell.swelling,.
splitting,.and.nanoscale.perforations.on.the.cell.membrane..We.have.additionally.shown.
how.the.AFM.can.be.used.to.quantify.the.size.and.number.of.cell.surface.granules.present.
on.chondrocytes.when.subjected.to.various.chemical.or.physical.treatments.(Iscru.et.al..
2008)—AFM.topographs.from.this.particular.study.are.highlighted.in.Figure.16.2C.
AFM.can.also.be.used.to.assess.the.interaction.with.or.uptake.of.nanotubes,.nanopar-
ticles,. or. biological. molecules. by. cells,. especially. when. it. is. combined. with. luorescence.
or. light. microscopy.. For. example,. Lampbretch. et. al.. used. AFM. to. image. noncovalently.
functionalized.single-walled.(SWCNTs).and.double-walled.carbon.nanotubes.(DWCNTs).
immobilized. on. different. biological. membranes,. such. as. plasma. membranes,. nuclear.
envelopes,. and. a. monolayer. of. avidin. molecules. (Lamprecht. et. al.. 2009).. The. uptake. of.
transferrin-conjugated. gold. nanoparticles. by. live. human. carcinoma. cells. has. also. been.
imaged.with.AFM.in.real.time.(Yang.et.al..2005)..In.this.study,.AFM,.combined.with.confo-
cal.microscopy,.was.able.to.visually.elucidate.the.role.of.transferrin.receptor.in.facilitating.
transferrin-mediated.drug.uptake.by.cells..In.addition.to.providing.detailed.topographs,.
the. AFM. can. also. provide. adhesive. or. mechanical. mapping. of. the. cell. surface—related.
techniques.are.detailed.in.Section.16.4.
The.surface.features.of.a.number.of.tissues.have.been.analyzed.using.AFM..For.instance,.
bone.has.been.studied.on.both.the.nano-.and.microscale..Thurner.et.al..(2007).used.AFM.
to.characterize.individual.collagen.type.I.ibers.and.their.∼67.nm.banding.directly.on.the.
