Fine Control Over the Size of Surfactant–Polyelectrolyte Nanoparticles by Hydrodynamic Flow Focusing

Synthesis of surfactant–polyelectrolyte nanoparticles was carried out in a microfluidic device with a fine control over the size and the polydispersity. An anionic polysaccharide (sodium carboxymethylcellulose, CMC) solution was focused using a cationic surfactant (dodecyl trimethylammonium bromide, DTAB) solution in a microfluidic channel at selected ratios of flow rates and reagent concentrations. The methodology ensured a controlled mixing kinetics and a uniform distribution of charges at the mixing interface. The resulting nanoparticles exhibited remarkably well-defined and repeatable size distributions, with hydrodynamic diameters tunable from 50 up to 300 nm and polydispersity index around 0.1 in most cases. Microfluidic-assisted self-assembly may be an efficient way to produce well-controlled polyelectrolyte-based nanoparticles suitable for colloidal science as well as for gene delivery applications.