James Dahlman, an assistant professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, holds a microfluidic chip used to fabricate nanoparticles that could be used to deliver therapeutic genes.
Credit: Rob Felt, Georgia Tech
Using tiny snippets of DNA as "barcodes,"
researchers have developed a new technique for rapidly screening the ability of
nanoparticles to selectively deliver therapeutic genes to specific organs of
the body. The technique could accelerate the development and use of gene
therapies for such killers as heart disease, cancer and Parkinson's disease.
Genetic
therapies, such as those made from DNA or RNA, are hard to deliver into the
right cells in the body. For the past 20 years, scientists have been developing
nanoparticles made from a broad range of materials and adding compounds such as
cholesterol to help carry these therapeutic agents into cells. But the rapid
development of nanoparticle carriers has run into a major bottleneck: the
nanoparticles have to be tested, first in cell culture, before a very small
number of nanoparticles is tested in animals. With millions of possible
combinations, identifying the optimal nanoparticle to target each organ was highly
inefficient.
Using
DNA strands just 58 nucleotides long, researchers from the University of
Florida, Georgia Institute of Technology and Massachusetts Institute of
Technology have developed a new testing technique that skips the cell culture
testing altogether -- and could allow hundreds of different types of
nanoparticles to be tested simultaneously in just a handful of animals.
The
original research was done in the laboratories of Robert Langer, the David H.
Koch Institute Professor, and Daniel Anderson, the Samuel A. Goldsmith
Professor of Applied Biology, at MIT. Supported by the National Institutes of
Health, the research was reported February 6 in the journal Proceedings of
the National Academy of Sciences.
"We
want to understand at a very high level what factors affecting nanoparticle
delivery are important," said James Dahlman, an assistant professor in the
Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and
Emory University, one of Langer's former graduate students, lead author on the
study, and one of the paper's corresponding authors. "This new technique
not only allows us to understand what factors are important, but also how
disease factors affect the process."
To
prepare nanoparticles for testing, the researchers insert a snippet of DNA that
is assigned to each type of nanoparticle. The nanoparticles are then injected
into mice, whose organs are then examined for presence of the barcodes. By
using the same technologies scientists use to sequence the genome, many nanoparticles
can be tested simultaneously, each identified by its unique DNA barcode.
Researchers
are interested not only in which nanoparticles deliver the therapeutics most
effectively, but also which can deliver them selectively to specific organs.
Therapeutics targeted to tumors, for example, should be delivered only to the
tumor and not to surrounding tissues. Therapeutics for heart disease likewise
should selectively accumulate in the heart.
While
much of the study was devoted to demonstrating control strategies, the
researchers did test how 30 different particles were distributed in eight
different tissues of an animal model. This nanoparticle targeting 'heat map'
showed that some particles were not taken up at all, while others entered
multiple organs. The testing included nanoparticles previously shown to
selectivity enter the lungs and liver, and the results of the new technique
were consistent with what was already known about those nanoparticles.
The
single-strand DNA barcode sequences are about the same size as antisense
oligonucleotides, microRNA and siRNA being developed for possible therapeutic
uses. Other gene-based therapeutics are larger, and additional research would
be needed to determine if the technique could be used with them. In the research
reported this week, the nanoparticles were not used to deliver active
therapeutics, though that would be a near-term next step.
"In
future work, we are hoping to make a thousand particles and instead of
evaluating them three at a time, we would hope to test a few hundred
simultaneously," Dahlman said. "Nanoparticles can be very complicated
because for every biomaterial available, you could make several hundred
nanoparticles of different sizes and with different components added."
Once
promising nanoparticles are identified with the screening, they would be
subjected to additional testing to verify their ability to deliver
therapeutics. In addition to accelerating the screening, the new technique may
require fewer animals -- perhaps no more than three for each set of
nanoparticles tested.
There
are a few caveats with the technique. To avoid the possibility of nanoparticles
merging, only structures that are stable in aqueous environments can be tested.
Only nontoxic nanoparticles can be screened, and researchers must control for
potential inflammation generated by the inserted DNA.
In
Langer and Anderson's laboratory, Dahlman worked with Kevin Kauffman, who
remains at MIT, and Eric Wang, now an assistant professor the University of
Florida. Other co-authors of the paper included Yiping Xing, Taylor Shaw,
Faryal Mir and Chloe Dlott, all of whom are at MIT.
"Nucleic
acid therapies hold considerable promise for treating a range of serious
diseases," said Dahlman. "We hope this technique will be used widely
in the field, and that it will ultimately bring more clarity to how these drugs
affect cells -- and how we can get them to the right locations in the
body."
Story
Source:
Materials
provided by Georgia Institute of Technology.
Original written by John Toon. Note: Content may be edited for style and
length.
Journal
Reference:
James
E. Dahlman, Kevin J. Kauffman, Yiping Xing, Taylor E. Shaw, Faryal F. Mir,
Chloe C. Dlott, Robert Langer, Daniel G. Anderson, Eric T. Wang. Barcoded
nanoparticles for high throughput in vivo discovery of targeted therapeutics.
Proceedings of the National Academy of Sciences, 2017; 201620874 DOI: 10.1073/pnas.1620874114
https://www.sciencedaily.com/releases/2017/02/170207105318.htm
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