DNA Labels Simplify Development of Drug Delivery Nanoparticles

A team of biomedical engineers developed a method for labeling potential drug delivery nanoparticles with DNA "barcodes," which allowed the tracing of the nanoparticles within living test animals.

The effectiveness of nucleic acid drugs is limited by inefficient delivery to target tissues and cells and by unwanted accumulation in off-target organs. Although thousands of chemically distinct nanoparticles can be synthesized, nanoparticles designed to deliver nucleic acids in vivo were first tested in cell culture, yielding poor predictions for delivery in vivo. To facilitate testing of many nanoparticles in vivo, investigators at the Georgia Institute of Technology the University of Florida and the Massachusetts Institute of Technology designed and optimized a high-throughput DNA barcoding system to simultaneously measure nucleic acid delivery mediated by dozens of distinct nanoparticles in a single mouse.

The "barcodes" were short (approximately 58 nucleotides long) stretches of DNA, in the same size range as antisense oligonucleotides, microRNAs, and siRNAs (short inhibiting RNAs). A unique DNA barcode sequence was inserted into each type of nanoparticle carrier to be tested. The nanoparticles were injected into mice, whose organs were then examined for presence of the barcode using standard gene mapping techniques.

The investigators reported in the February 6, 2017, online edition of the journal Proceedings of the [U.S.] National Academy of Sciences that the method distinguished previously characterized lung- and liver- targeting nanoparticles and accurately reported relative quantities of nucleic acid delivered to tissues. Barcode sequences did not affect delivery, and no evidence of particle mixing was observed for tested particles. By measuring the bio-distribution of 30 nanoparticles to eight tissues simultaneously, they identified chemical properties promoting delivery to some tissues relative to others. Finally, particles that distributed to the liver also silenced gene expression in hepatocytes when formulated with siRNA.

"We want to understand at a very high level what factors affecting nanoparticle delivery are important," said first author Dr. James Dahlman, assistant professor of biomedical engineering at the Georgia Institute of Technology. "This new technique not only allows us to understand what factors are important, but also how disease factors affect the process. 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."

"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," said Dr. Dahlman. "Nanoparticles can be very complicated because for every biomaterial available, you could make several hundred nanoparticles of different sizes and with different components added."