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DNA compaction in a microfluidic channel

Researchers from the Laboratoire de Physique des Solides and the Institute of Bioengineering and Nanotechnology in Singapore have devised a simple and fast microfluidics-based method for the control of DNA compaction into nanoparticles with well-defined sizes. This class of self-assembled nanoparticles holds a great potential for gene therapy, and a fine control over the size distribution should enable a more efficient and less toxic gene delivery with respect to the traditional bulk methods of preparation.

Synthesis of innovative nanomaterials mostly relies on molecular self-assembly, a process by which individual components spontaneously form elaborate ordered structures with emerging functions. Polyelectrolyte-based complexes constitute an important class of soft nanoparticles that rely on electrostatic interactions between a polyelectrolyte and an oppositely-charged agent. When the polyelectrolyte is made of therapeutic nucleic acids, the resulting complexes hold a great potential for gene therapy. One of the reasons why the development of gene therapy has been limited so far is the lack of efficient and nontoxic vector. Synthetic vectors prepared by traditional bulk mixing display polydisperse morphological characteristics. In particular, their size is poorly controlled, which gives rise to low transfection efficiencies – the vectors are too large to diffuse within tissues – or to nonrepeatable results.

(Left) Optical image of the microchannels at the confluence of the three streams containing DNA, water, and surfactant.(Middle) Electron micrographs of surfactant-DNA nanoparticles. (Right) Schematics of a nanoparticle made up of DNA (in blue) compacted by cationic surfactants (in red).

Researchers from the Laboratoire de Physique des Solides and the Institute of Bioengineering and Nanotechnology in Singapore have devised a series of microfluidic devices that enabled to tune the mixing time of two fluids with respect to the adsorption time between oppositely-charged molecules. By adjusting the flow rates between a central stream focused by two side streams, each of which contained either DNA, surfactants or solvent, the self-assembly process could be directed to yield nanoparticles with small sized. The researchers thus associated by slow diffusion cationic surfactants with about 2,000-base-pairs DNA molecules and formed nanoparticles with diameters close to 30 nm. So small objects likely contained one or two DNA molecules at most. This microfluidics-driven strategy is quite general and can presumably be applied to systems with diverse self-assembly kinetics. It might open attractive opportunities for the directed self-assembly of complex soft nanomaterials, especially for biomedical applications.

Reference :

Microfluidics-Driven Strategy for Size-Controlled DNA Compaction by Slow Diffusion through Water Stream
Ciprian Iliescu and Guillaume Tresset
Chem. Mater. 27, 8193-8197 (2015).

Contact :

Guillaume Tresset