Micro-RNA Nanoparticles for Gene Silencing: Measuring Size and Zeta Potential with Light Scattering Technology

RNA interference is a highly promising gene silencing technique in which translation of the target gene’s messenger RNA (mRNA) is inhibited by short complementary RNA sequences. These include the so-called small interfering-RNAs (siRNA), which are double-stranded and whose sequence is perfectly complementary to that of the target mRNA, therefore acting with a high degree of specificity, and the single-stranded micro-RNAs (miRNA), which can interfere with a broader range of targets through imperfect pairing.

One of the biggest challenges of RNA interference is the difficulty to deliver intact siRNA/miRNA across the cell membrane and into the cytosol while preserving cell viability. Intracellular delivery of RNA by transfection using peptide-based nanoparticles has shown promise. Such vectors are composed of the negatively charged nucleic acids and positively charged peptides, which co-assemble spontaneously into nanoparticles in solution. The arginine-rich peptide protamine forms nanoparticles that are predicted to exhibit good cell-penetrating properties and lower cytotoxicity than other commercially available transfection reagents.

The naturally occurring micro-RNA miR-27a has been shown to efficiently suppress expression of the adipogenic marker PPARγ (Peroxisome proliferator- activated receptor gamma), thereby blocking adipocyte differentiation. For this reason, miR-27a-protamine nanoparticles may represent a new therapeutic approach to prevent metabolic complications associated with diabetes and obesity.

Since nanoparticle properties such as size and zeta potential may influence particle uptake by target cells and/or tissues in vivo, light scattering technologies represent an important tool to investigate the physicochemical properties of miRNA-delivery systems. Here we demonstrate that the Litesizer™ 500 returns rapid and precise results despite very low sample concentration and volume. We used dynamic light scattering (DLS) for particle size measurement and a novel patented electrophoretic light scattering technology called cmPALS for zeta potential determination.

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