Biomedical Engineering Reference
In-Depth Information
pellets. while. placing. the. magnet. on. the. side. wall. of. the. tubes,. and. few. bacterial. cells.
remained.in.the.supernatant,.while.the.rest.were.captured.in.the.MMN-bacterial.aggre-
gates.toward.the.magnet.
When. MMNs. were. used. to. capture. bacterial. contaminants,. especially. coliforms,. in. the.
wastewater.samples.while.applying.the.magnet.to.the.side.wall.of.the.tubes,.both.the.super-
natant.and.pellet.were.examined.under.a.TEM.(Figure 17.5a.and.b)..The.supernatant.showed.
a.reduction.of.a.factor.of.10
3
-10
4
.of.bacterial.counts.(cfu/ml),.while.the.magnet.was.applied.
to.the.side.walls.of.the.tubes.(Table 17.2),.and.a.reduction.of.bacterial.counts.was.observed:.a.
factor.of.10
2
-10
3
.for.grey.water.(Table 17.3)..This.indicates.that.MMNs.are.used.for.fast.detec-
tion.and.capturing.of.bacterial.cells.(10-20.min.maximum),.compared.to.the.currently.avail-
able.and.used.methodologies.(2-7.days),.and.applying.MMNs.serves.as.an.ideal.method.of.
choice.for.water.quality.and.rapid.detection.and.removal.of.bacterial.contaminants.
When.a.mixture.of.MMNs.and.
Salmonella
.cell.samples.was.sectioned.using.an.ultrami-
crotome.and.examined.under.a.TEM.to.reveal.the.inside.of.bacterial.cells,.the.results.clearly.
showed.that.MMNs.did.enter.inside.bacterial.cells.(Figure 17.6)..The.real.mechanism(s).by.
which.MMNs.entered.inside.bacterial.cells.through.the.cell.wall.and.cell.membrane.bar-
riers.is.not.really.known,.and.was.not.investigated.in.this.study..The.suggestion.is.that.it.
may.be.through.protein-like.siderephore.compounds.secreted.by.bacterial.cells.to.capture.
MMNs,.or.receptor-like.compounds.on.the.surface.of.the.bacterial.cells.that.capture.the.
MMNs.and.engulf.them.inside,.or.by.invagination.of.the.cell.membrane.
The. MMNs,. when. tested,. proved. to. have. no. effect. on. bacterial. growth. and. viability.
when.the.growth.inhibition.zone.method.was.applied..In.fact,.the.MMNs.were.composed.
of. nutrient. elements. (mainly. Fe. and. Zn),. which. promoted. bacterial. growth. and. had. no.
killing. effect.. It. was. also. indicated. in. this. study. that. MMNs. penetrated. inside. bacterial.
cells.as.revealed.by.thin-section.imaging.under.a.TEM.
In. conclusion,. in. the. application. of. MMNs,. wherein. minimal. facilities. and. infrastruc-
tures. are. needed,. minimal. amounts. of. MMNs. (4-6. mg/ml). are. required. to. detect. and.
decontaminate. bacterial. pathogens,. and. inexpensive. procedures. for. both. detection. and.
decontamination.of.microbial.pathogens.are.used..Furthermore,.no.staining.is.needed.to.
detect.the.presence.of.bacterial.cells.
References
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