From near hard spheres to colloidal surfboards.

This work revisits the synthesis of the colloidal particles most commonly used for making model near hard suspensions or as building blocks of model colloidal gels, i.e. sterically stabilised poly(methyl methacrylate) (PMMA) particles. The synthesis of these particles is notoriously hard to control and generally the problems are ascribed to the difficulty in synthesising the graft stabiliser (PMMA-g-PHSA). In the present work, it is shown that for improving the reliability of the synthesis as a whole, control over the polycondensation of the 12-polyhydroxystearic acid is the key. By changing the catalyst and performing the polycondensation in the melt, the chain length of the 12-polyhydroxystearic acid is better controlled, as confirmed by 1H-NMR spectroscopy. Control over the graft copolymer now enables us to make small variations of near hard sphere colloids, for example spherical PMMA particles with essentially the same core size and different stabilising layer thicknesses can now be readily produced, imparting controlled particle softness. The PMMA spheres can be further employed to create, in gram scale quantities, colloidal building blocks having geometrical and/or chemical anisotropy by using a range of mechanical deformation methods. The versatility of the latter methods is demonstrated for polystyrene latex particles as well.

One-step production of darunavir solid dispersion nanoparticles coated with enteric polymers using electrospraying.

OBJECTIVES: The aim of this work was to investigate the feasibility of producing darunavir (DRV) solid dispersion nanoparticles coated with an enteric polymer in one single step using electrospraying. METHODS: The core-shell nanoparticles were made using coaxial electrospraying. A solution of DRV with hydroxypropyl methylcellulose in a mixture of organic solvents formed the core, while the shell was produced from an enteric polymer (Eudragit L100) dissolved in an organic solvent. The final particles were evaluated in terms of morphology, physical state, encapsulation efficiency and in-vitro dissolution. KEY FINDINGS: Nanoparticles of encapsulated DRV solid dispersions within Eudragit L100 were successfully prepared with high encapsulation efficiency (90%). The enteric coating layer reduced the percentage of DRV release in acidic medium in the in-vitro dissolution test to less than 20%. CONCLUSIONS: This study showed the potential of coaxial electrospraying for encapsulating solid dispersions within core-shell structured nanoparticles.