Exploring the colloidal stability of curcumin nanoparticles formed by nanoprecipitation.

Pure curcumin nanoparticles were prepared by antisolvent precipitation using acetone as the solvent and water as the antisolvent, offering a simple and food-compatible strategy to enhance curcumin dispersibility in aqueous environments. The colloidal stability of the aqueous dispersions was assessed by static multiple light scattering. Progressive particle size growth led to sedimentation. This study then focused on the stability of nanoprecipitated curcumin prior to sedimentation, in order to unambiguously determine the mechanisms responsible for destabilization. Particle size evolution over time was monitored by dynamic light scattering. The physical state of curcumin was determined by 1H NMR and XRD analyses, confirming that neither coalescence nor crystallization occurred. Ostwald ripening was successfully confirmed by modeling the particle growth kinetics using the Lifshitz-Slyozov-Wagner (LSW) theory. Nevertheless, it is known that the LSW model remains superficial. That is why an original approach is used in this study to validate the destabilization mechanism. This involves varying the composition of the solvent in order to modify the solubility of curcumin in the continuous phase, a key parameter in the context of Ostwald ripening. Thus, varying the acetone content demonstrated the role of curcumin solubility in governing dispersion stability, confirming that Ostwald ripening occurred, as faster particle growth was observed at higher acetone levels. Moreover, curcumin solubility in the continuous phase derived from the LSW model was consistent with measurements performed by HPLC. These findings demonstrated that amorphous curcumin nanoparticles undergo Ostwald ripening in stabilizer-free aqueous systems, with ripening rates controlled by solvent-induced solubility changes.