Genetic therapies, such as those made from DNA or RNA, are hard to
deliver into the right cells in the body. 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.
‘Using DNA strands just 58 nucleotides long, researchers 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.’
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 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
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."