48 THE SCIENTIST | the-scientist.com
Horizon Discovery Dharmacon Edit-R
Fluorescent Cas9 Nuclease mRNA
AcouSort AcouWash
In 2010, researchers at Lund University in
Sweden developed the concept of using
sound to migrate cells, a phenomenon
called acoustophoresis. That December,
they launched AcouSort to commercialize
the technology. Earlier this year, the com-
pany officially launched its second product,AcouWash, which can wash cells from one
medium to another, enrich or concentrate
cell samples, and separate cells based on
size, all using ultrasound.
An acoustic wave “pushes particles or
cells of a certain size into the center of [a]
microchannel that the sample is passing
through,” explains Jay Mallinson, lead engi-
neer on the $50,000 benchtop machine.
Researchers can adjust the ampli-
tude of the acoustic wave depend-
ing on the size of the cells they
are trying to isolate—larger cells
actually need less force to move
because there is more surface area
to be pushed by the acoustic wave.
Then, it’s just a matter of directing
the flow through a splitter that sep-
arates the cells of interest from the
background media.
AcouWash minimizes cell loss,
which can happen with repeated
washing and centrifugation steps—a big advantage when working with sam-
ples containing precious few cells, says
Karolina Pircs, a postdoc in Johan Jakobsson’s
molecular neurogenetics lab at Lund Uni-
versity. Pircs’s research involves directly
reprogramming fibroblasts from Hun-
tington’s patients and healthy controls
into neurons. A protocol that she helped
develop last year (EMBO Mol Med, 9:1117–
131) converts 30 percent to 40 percent of
the fibroblasts, meaning the researchers
must sort the converted from unconverted
cells. The AcouWash system, which she’s
tested twice so far, yielded about 10 per-
cent more cells than a traditional protocol
involving six centrifugation steps, she says.VAN VLIET:“While the function of this inven-
tion is simple, its capacity to handle small sample
volumes at relatively low shear rates is an attrac-
tive option for intermittent sampling and analysis
of cells during process development and manu-
facturing protocol optimization."To use the genome-editing tool CRISPR-Cas9,
researchers typically insert DNA, coding for
the various components of the tool, into cells
they want to edit. But there’s no easy way of
getting rid of this foreign DNA once it’s been
incorporated into the host cell.
Specifically, researchers may be con-
cerned about the lingering presence of DNA
that codes for the Cas9 nuclease. Often
“you have the Cas9 still being expressed in
the cell long after the edit has occurred,”
says Amanda Haas, a product manager at
UK-based gene-editing company Horizon
Discovery. That means that the enzyme
can still interact with host DNA, potentially
leading to unwanted cuts in the genome at
off-target sites.
One of the company’s latest products,
Dharmacon Edit-R Fluorescent Cas9 Nucle-ase mRNA, aims to circumvent
this problem by providing the
RNA transcript instead of DNA
for the Cas9 enzyme. Soon after
a target cell has synthesized the
protein—which is fluorescent to
aid cell sorting, Haas notes—the
mRNA is naturally degraded. So
“while the edits you’ve made are
permanent,” she explains, “you
won’t have remnants of the edit-
ing system still present.”
Dharmacon Edit-R Fluorescent
Cas9 Nuclease mRNA retails from
Horizon Discovery at $400 for a
ready-to-use tube of 20 micrograms—enough
mRNA to do several experiments, Haas says.
Horizon Discovery was unable to locate a user
who could comment on the product.KOELHER:“This reasonably priced tool
enables FACS enrichment of edited cell popula-
tions. My lab would use this product, and I think
it could impact several projects.”