Preparation of ionically cross-linked pectin nanoparticles in the presence of chlorides of divalent and monovalent cations.

Nanoparticles were prepared by ionotropic gelation of low-methoxylated (LM) and amidated low-methoxylated (AM) pectin with zinc chloride (ZnCl2) in aqueous media. The samples were characterized by atomic force microscopy, dynamic light scattering, turbidimetry, zeta potential, and pH measurements. Pectin nanoparticles could be prepared at a pectin concentration of 0.07% (w/w) and a ZnCl2-to-pectin ratio of 15:85 (w/w) in the presence of sodium chloride, but not in pure water. Interestingly, particles in the nanometer size-range could also be prepared in the absence of the cross-linker ZnCl2. The dynamic light scattering studies revealed that the AM-pectin nanoparticles were much less polydisperse than the LM-pectin nanoparticles. The AM-pectin nanoparticles were therefore considered to be more promising as a potential drug delivery system, and further studies were performed to investigate the colloidal stability and the effect of the pectin concentration on the size, charge, and compactness of these nanoparticles.