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In efforts to develop a new gene therapy technique, researchers from the Autonomous University of Barcelona (UAB) have encapsulated genetic material and then released it inside the nuclei of cells, using disc-shaped particles measuring only a few nanometers. The particles, which the scientists have dubbed nanodiscs, rapidly cross the cell membrane and concentrate in the nucleus, providing higher gene transfer efficiency than that obtained through other mechanism.

One of the challenges in gene therapy —which aims to treat diseases using nucleic acids (DNA or RNA)— is to deliver this material directly to the nuclei of cells without any substantial loss of material and without any side effects. Thus, scientists explore different types of vectors to shuttle the genetic material to the desired target. Currently, the most widely used vectors in clinical trials are deactivated natural viruses. However, these often provoke side effects that limit their therapeutic utility.

Artificial viruses are among the most promising alternatives to natural viruses for use as gene therapy shuttles. These can be assembled through genetic engineering, by linking together small proteins, which are in turn composed of peptides.

The UAB research team is led by professor Antonio Villaverde, of UAB’s Department of Genetics and Microbiology, researcher at UAB’s Institute of Biotechnology and Biomedicine and at the CIBER-BBN. They have shown that a peptide called R9, comprising nine units of the same amino acid (arginine), can encapsulate genetic material, and then agglutinate with other R9 molecules to form nanoparticles, which then penetrate cells and travel directly into the nucleus to deliver the genetic cargo. These nanoparticles are disc-shaped, and only 20 nanometers in diameter and three nanometers thick.

Their research, recently published in the journals Biomaterials and Nanomedicine, included studying the behavior of R9 nanodiscs inside cells using confocal microscopy, performed by Dr. Mònica Roldán of UAB’s Microscopy Service. The images reveal that, once the particles have crossed the cell membrane, they move directly to the nucleus at a speed of 0.0044 micrometers per second—ten times as fast as they would move by passive transport. Thus, they accumulate inside the nucleus, and not inside the cytoplasm (the bulk of the cell’s interior), which contributes to their great efficacy. In fact, one of the team’s microcopy images was selected by the journal Biomaterials as one of their Top Twelve Images of 2010.

The discovery, which also drew on the efforts of researchers from the Institute of Materials Science of Barcelona (ICMAB-CSIC), the Catalan Institution for Research and Advanced Studies (ICREA) and the Universitat Politècnica de Catalunya, has pioneered a new class of therapeutic nanoparticles. According to project manager Dr. Esther Vázquez, “The nanodiscs self-assemble, move rapidly, remain stable throughout their trajectory, and travel to the inside of the nucleus. Thus, they are highly promising as prototypes for the safe delivery of nucleic acids and functional proteins”.

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