Home' Technology Review : May 2005 Contents 86
From the Lab
FROM THE LAB
tainer, samples tested with it are less likely
to be contaminated by researchers or the
environment, and samples containing
pathogens are less likely to infect workers.
Assuming patient samples can be pre-
pared easily for chip analysis, the chip
could also make it easier to detect DNA
variations in settings less controlled than
a research lab. Though the research is still
in its initial phases, Hitachi expects that
the chips could be used in clinics or small
hospitals to help doctors decide which
dr ugs to prescribe for patients.
Source: Yazawa, Y., et al. 2005. A wireless biosensing
chip for DNA detection. Paper presented at 2005 IEEE
International Solid-State Circuits Conference. Feb. 6--
10. San Francisco, CA.
Pig hearts in humans?
: When he was a heart surgeon,
David Cooper would have 140 patients
referred to him for transplants each year;
because of the shortage of donor organs,
only about 25 would receive them. Now
an academic researcher at the University
of Pittsburgh Medical Center, Cooper is
part of a broad e ort to search for ways to
use pig organs for human transplants.
Without extremely high levels of im-
munosuppressive dr ugs, pig organs sel-
dom last for half an hour in, say, baboons.
The organs swell up and turn black and
must be removed quickly, or the animals
may die. Cooper led a team of scientists
from Harvard Medical School and Im-
merge Biotherapeutics in determining
what would happen when hearts from
pigs genetically modi ed to seem less
"piglike" to a foreign immune system
were transplanted into baboons.
: The baboon s im-
mune system targets the pig organs for at-
tack mainly because of a particular sugar
that covers porcine blood vessels. Three
years ago, scientists created pigs unable to
make this sugar by deleting a gene for a
certain enzyme. Cooper s team trans-
planted hearts from the genetically modi-
ed pigs onto the abdomens of eight
baboons, where the researchers could tell
how strongly the pig hearts were beating.
Three baboons died for reasons other
than organ rejection, and the hearts re-
mained viable. In the other ve baboons,
the hearts stopped beating between 59
and 179 days after transplantation, at
which time they were surgically removed.
The small blood vessels in the organs were
full of tiny clots, probably caused by a mis-
match between tissues and blood-clotting
systems. But the researchers found evi-
dence that this clotting process can be at
least slowed with anticlotting medicines,
like aspirin. None of the baboons su ered
serious infections as part of the study.
: Cooper and colleagues
study marks the rst transplant using pigs
engineered to lack a gene and the rst
time xenotransplanted organs have sur-
vived for months when immunosuppres-
sive dr ugs were administered in doses
similar to those used in humans. It also
marks the longest time a pig heart has
survived in another species. In previous
work, organ rejection has been inhibited,
though not as dramatically, by using pigs
engineered to contain human genes that
protect their organs from the human im-
mune system. Experiments using addi-
tional pigs with these human genes and
without the pig sugar gene are planned,
but the rst pig-to-human transplants are
years away, says Cooper. First, xenotrans-
plants must be deemed as likely to help
patients as other available treatments,
like mechanical heart-assistive devices.
Even then, concerns about ethics and in-
fectious disease must be addressed.
Source: Kuwaki, K., et al. 2005. Heart transplantation
in baboons using α1,3-galactosyltransferase gene-
knockout pigs as donors: initial experience. Nature
An atomically sharp device
: To build useful small devices,
engineers must be able to see what they
are doing, so they use atomic force micro-
scopes to take pictures with nanometer
resolution. To create images, the micro-
scopes move a sharp tip across the sur-
faces of such tiny objects as silicon
transistors or DNA molecules. The tip,
just a few atoms across, moves slowly: at
best, commercial atomic force micro-
scopes can take only about one image ev-
ery ten seconds. So they re not much use
in studying fast processes. Now, research-
ers at MIT have found a way to capture
nanoscale images a million times faster.
: The technique
developed by Mekhail Anwar and Itay
Rousso yields high-speed movies of pro-
cesses that repeat regularly. An object to
be imaged is set in motion, and the tip
captures infor mation about surface
height at one location only. Once enough
data is collected, the tip moves a few
nanometers to its next location, and the
process is repeated. Each location thus
becomes a pixel in a motion picture, and
aligning the pixels in time produces a
time-lapse movie of the process.
Unconstrained by the rate at which it
can move for ward, the tip collects data as
quickly as its up-and-down movements
can be recorded. Anwar and Rousso
demonstrated the potential of their tech-
nique by imaging the motion of a micro-
device with a time resolution of ve
: Because they scan
slowly, atomic force microscopes are now
used only to take snapshots of surfaces.
Atomic force movies could help research-
ers analyze the motions of the micro u-
idic pumps used in the puri cation and
analysis of DNA and proteins or provide
moving images of biological processes.
Since any atomic force microscope
could, in theory, be programmed to pro-
duce such movies, academic and indus-
trial researchers have the means, motive,
and opportunity to try the technique.
Thus, nano moviemaking could become
an important way to help researchers see
what molecular devices are doing, ana-
lyze their performance, and determine
how to improve them.
Source: Anwar, M., and I. Rousso. 2005. Atomic force
microscopy with time resolution of microseconds.
Applied Physics Letters 86:014101.
Links Archive June 2005 April 2005 Navigation Previous Page Next Page