BioMEMS for Cell Biology - Introduction to BioMEMS - page 362

Using a simple oxygen gradient generator (one inlet with oxygen, one inlet with nitrogen,
and a central PDMS chamber illed with the worms, all assembled on agar—a substrate onto
which C. elegans crawls easily and bacteria thrive, so it is a good mimic of the worm's natural
soil substrate), in 2004, the Bargmann group found that the worms avoid both high and low
oxygen concentrations ( Figure 6.69 ); however, they cluster where the concentration of oxygen
is between 5% and 10%, which suggests a plausible mechanism for seeking the environments
created by oxygen-consuming bacteria (on which the worms feed).
As it happens, C. elegans can also be manipulated very eiciently with microluidics, as we
saw in Chapter 5 (see Figure 5.60 ). Fatih Yanik's laboratory at MIT has developed microlu-
idic systems containing pneumatic microactuators that immobilize the worms in speciic loca-
tions of the device in which they undergo femtosecond laser “surgery” (e.g., axotomy) or simply
imaging (e.g., for screening), as shown in Figure 6.70 . In a typical experiment, a neuron with a

21% 15% 10% 5% 0%

O 2

FIGURE 6.69 First. use. of. C. elegans . in. microluidics.. The. worms. have. been. digitally. added. to.
convey.their.relative.density.in.the.device..(From.J..M..Gray,.D..S..Karow,.H..Lu,.A..J..Chang,.J..S..
Chang,.R..E..Ellis,.M..A..Marletta,.and.C..I..Bargmann,.“Oxygen.sensation.and.social.feeding.medi-
ated.by.a. C. elegans .guanylate.cyclase.homologue,”. Nature .430,.317,.2004..Figure.contributed.by.
Cori.Bargmann.)

(a) (b) (c)

i

ii

Axons
Cell bodies

iii

FIGURE 6.70 Recording.and.manipulation.of. C. elegans .nervous.system..Scale.bar.is.250.μm..In.
(c),. the. labeled. neurons. are. GFP-labeled. luorescent. posterior. lateral. mechanosensory. neurons..
(From.Fei.Zeng,.Christopher.B..Rohde,.and.Mehmet.Fatih.Yanik,.“Sub-cellular.precision.on-chip.
small-animal.immobilization,.multi-photon.imaging.and.femtosecond-laser.manipulation,”. Lab Chip .
8,.653-656,.2008..Reproduced.with.permission.from.The.Royal.Society.of.Chemistry.)