Synthesis and characterisation of zein-curcumin colloidal particlesElectronic supplementary information (ESI) available: DSC thermograms of zein, curcumin, blank zein colloidal particles and zein-curcumin (Z : C = 5 : 1) composite colloidal particles. See DOI: 10.1039/c0sm00800a

Zein-curcumin composite colloidal particles were synthesized using an antisolvent precipitation method. The average particle size could be controlled down to 100-150 nm, depending on the solvent system and the ratio of zein and curcumin used in the synthesis. In all cases, spherical particles were obtained, as confirmed by transmission electron microscopy. Depending on the preparation conditions, curcumin load and encapsulation efficiency varied from 1.6 to 4.1% and 71.1 to 86.8%, respectively. Solid state characterization by differential scanning calorimetry and X-ray diffraction indicated the amorphous nature of entrapped curcumin. An UV irradiation study confirmed enhanced photostability of curcumin due to the entrapment of curcumin in the biopolymeric matrix. The particles were also found to have good colloidal stability at a broad range of physiologically relevant pH (1.2, 4.5, 6.7 and 7.4) and in simulated gastro-intestinal conditions. Results from an in vitro mucoadhesion study showed retention of more than 60% curcumin for 150 minutes. The mucoadhesion property was further confirmed from a mucin association study carried out on Caco-2 cells. We present for the first time preparation of zein-curcumin composite colloidal particles with enhanced pH and photostability, stability in GI conditions and mucoadhesive properties.