Assembly of foxtail millet prolamin/chitosan hydrochloride/carboxymethyl-beta-cyclodextrin in acetic acid aqueous solution for enhanced curcumin retention

The aim of this work is to investigate the assembly of foxtail millet prolamin (FP) with chitosan hydrochloride (CHC) and carboxymethyl-beta-cyclodextrin (CMCD) in acetic acid aqueous solutions. The proportion of acetic acid has a positive impact on the disintegration of FP. With the use of 91.0 % (v/v) acetic acid, FP forms smaller particles of approximately 45 nm (naked FP particles) and 220 nm (FP - CHC - CMCD hybrid particles). In the case of using 61.5 % (v/v) acetic acid, the microstructures of bare FP particles and 570 nm composite FP nanoparticles (NPs) are looser, about 485 nm. Acetic acid inhibits the noncovalent bonds, including the hydrophobic interactions, hydrogen bonding and electrostatic attractions between FP and polysaccharides. Therefore, 3.8 % (v/v) acetic acid can nucleate FP to form more compact FP hybrid particles for delivering curcumin (Cur) with higher encapsulation efficiency, storage stability and release performance, and improve the antibacterial and anticancer activity of Cur.