Safe Delivery of Therapeutic Genes by DNA Barcoding

Researchers used small snippets of DNA as “barcodes” to develop a new technique for rapidly screening the capability of nanoparticles to selectively deliver therapeutic genes to particular organs of the body. This new technique succeeded in accelerating the development and use of gene therapies for Parkinson’s disease, cancer and heart disease.

It is difficult to deliver genetic therapies, such as those made from RNA or DNA, into the correct cells in the body. For the past two decades, scientists have been producing nanoparticles from a wide range of materials and also by adding compounds like cholesterol in order to help transmit these therapeutic agents into cells.

However, the speedy development of nanoparticle carriers has resulted into a major blockage. This major bottleneck refers to the fact that the nanoparticles will first have to be tested in cell culture, before a minimal number of nanoparticles is tested in animals. Identifying the optimal nanoparticle to target individual organs was increasingly inefficient with millions of possible combinations.

Researchers from the University of Florida, Georgia Institute of Technology and Massachusetts Institute of Technology used DNA strands only 58 nucleotides long to develop a new testing technique that skips the cell culture testing on the whole and further permits the simultaneous testing of hundreds of varied types of nanoparticles in only a handful of animals.

The original research was carried out 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. The research was supported by the National Institutes of Health and was reported in the February 6^th issue of 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. This new technique not only allows us to understand what factors are important, but also how disease factors affect the process.

James Dahlman, Assistant Professor, Georgia Tech and Emory University

The researchers prepared nanoparticles for testing by inserting a snippet of DNA assigned for all types of nanoparticles. This was followed by injecting the nanoparticles into mice, whose organs were further examined for the existence of the barcodes. Several nanoparticles can be simultaneously tested by using the same technologies scientists use to sequence the genome, where each nanoparticle is identified by its unique DNA barcode.

Researchers show interest on which nanoparticles deliver the therapeutics in an extremely effective manner and also on which nanoparticles can deliver them selectively to specific organs. Therapeutics targeted to tumors, for instance, should be delivered only to the tumor and not to the tissues surrounding the tumor. Likewise, therapeutics for heart should selectively gather in the heart.

The researchers tested how 30 different particles were distributed in eight different tissues of an animal model even though most of the study focused on demonstrating control strategies. This nanoparticle targeting ‘heat map’ pointed out that a few particles were not taken up at all, whereas others entered multiple organs.

The testing included nanoparticles earlier shown to selectivity enter the liver and lungs, and the results of the technique were consistent with what was previously known about those nanoparticles.

The single-strand DNA barcode sequences are almost the same size as antisense oligonucleotides, siRNA and microRNA being produced for possible therapeutic uses. Other gene-based therapeutics are considered to be larger, and additional research will help determine if the technique could be used with them. In this week’s research, the nanoparticles were not used to deliver active therapeutics even though that would in fact 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. Nanoparticles can be very complicated because for every biomaterial available, you could make several hundred nanoparticles of different sizes and with different components added.

James Dahlman, Assistant Professor, Georgia Tech and Emory University

After identifying promising nanoparticles with the screening, these nanoparticles are then sent for additional testing in order to verify their potential for delivering therapeutics. In addition to accelerating the screening, the new technique may also need fewer animals, not more than three for each set of nanoparticles tested.

This new technique has a few limitations. Only structures firm in aqueous environments can be tested to prevent the possibility of merging of nanoparticles. It is possible to screen only nontoxic nanoparticles, and researchers must control for possible inflammation produced by the inserted DNA.

In Langer and Anderson’s laboratory, Dahlman worked with Kevin Kauffman, who remains at MIT, and Eric Wang, currently an assistant professor the University of Florida. Yiping Xing, Taylor Shaw, Faryal Mir and Chloe Dlott, all from MIT, are the other co-authors of the paper.

Nucleic acid therapies hold considerable promise for treating a range of serious diseases. 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.

James Dahlman, Assistant Professor, Georgia Tech and Emory University