Production of PEGylated nanocapsules through solvent-displacement in confined impinging jets mixers

The growth of importance of nanocapsules (and other particulate systems) in different fields requires fast and reproducible methods for their production. Confined impinging jet mixers were successfully used for the production of nanospheres and are now tested for the first time for the production of nanocapsules. This work focuses on the understanding of formation mechanisms and on the quantification of the effect of the most important operating parameters involved in their production. Solvent displacement is employed here for the assembly of the nanocapsules by using a PEGylated derivative of cyanoacrylate as copolymer. A comparison with nanospheres obtained under the same operating conditions is also reported. Results show that the oil-to-copolymer mass ratio (MR) is the main factor affecting the final size distribution and that small nanocapsules are obtained only at low oil-to-copolymer MR. The effect of mixing is significant, proving that mixing of solvent and antisolvent also affects the final size distribution; this depends mainly on the inlet jet velocity, but the size of the mixer is also important. The Reynolds number may be useful to take this into account for geometrically similar systems. Quenching by dilution allows to stabilize the nanocapsules, evidencing the role of aggregation and ripening.