Tuning Alginate Microparticle Size via Atomization of Non-Newtonian Fluids.

A new approach based on the atomization of non-Newtonian fluids has been proposed to produce microparticles for a potential inhalation route. In particular, different solutions of alginate were atomized on baths of different crosslinkers, piperazine and barium chloride, obtaining microparticles around 5 and 40 microns, respectively. These results were explained as a consequence of the different viscoelastic properties, since oscillatory analysis indicated that the formed hydrogel beads with barium chloride had a higher storage modulus (1000 Pa) than the piperazine ones (20 Pa). Pressure ratio (polymer solution-air) was identified as a key factor, and it should be from 0.85 to 1.00 to ensure a successful atomization, obtaining the smallest particle size at intermediate pressures. Finally, a numerical study based on dimensionless numbers was performed to predict particle size depending on the conditions. These results highlight that it is possible to control the microparticles size by modifying either the viscoelasticity of the hydrogel or the experimental conditions of atomization. Some experimental conditions (using piperazine) reduce the particle size up to 5 microns and therefore allow their use by aerosol inhalation.