Influence of Hofmeister anions on structural and thermal properties of a starch-protein-lipid nanoparticle.

A self-assembled soluble nanoparticle, composed of common food biopolymers (carbohydrate, protein) and lipid, was previously reported by our laboratory. Although carrying capacity of valuable small molecules was demonstrated, physical functional properties are also important. Given the stabilization or destabilization characteristics of Hofmeister anion on macromolecular structures, mainly on proteins, here, we investigated the effects of different sodium salts composed of different Hofmeister anions on the structural and thermal properties of these self-assembled nanoparticles for improved functionalities. The salts were added into the mixture that was prepared in a diluted system during nanoparticle formation. Increased concentration of kosmotropic anions, in contrast to the chaotropic anion tested, resulted in nanoparticles with higher molar mass, hydrodynamic radius, and molecular density with more compact arrangement. The nanoparticles produced in presence of kosmotropic anions dissociated at higher temperatures and required higher enthalpies compared to the control sample. Spherical nanoparticles were formed for the kosmotropes with shear thinning behavior, contrary to rod-like nanoparticles for the chaotrope with near-Newtonian behavior. These findings help to gain an understanding of the effect of altering environmental conditions on the nanoparticles with an aim of producing desired structures for applications.

Self-assembled nanoparticle of common food constituents that carries a sparingly soluble small molecule.

A previously reported nanoparticle formed through the self-assembly of common food constituents (amylose, protein, and fatty acids) was shown to have the capacity to carry a sparingly soluble small molecule (1-naphthol) in a dispersed system. Potentiometric titration showed that 1-naphthol locates in the lumen of the amylose helix of the nanoparticle. This finding was further supported by calorimetric measurements, showing higher enthalpies of dissociation and reassociation in the presence of 1-naphthol. Visually, the 1-naphthol-loaded nanoparticle appeared to be well-dispersed in aqueous solution. Molecular dynamics simulation showed that the self-assembly was favorable, and at 500 ns, the 1-naphthol molecule resided in the helix of the amylose lumen in proximity to the hydrophobic tail of the fatty acid. Thus, sparingly soluble small molecules, such as some nutraceuticals or drugs, could be incorporated and delivered by this soft nanoparticle carrier.

Chitosan-alginate multilayer beads for gastric passage and controlled intestinal release of protein.

Chitosan-alginate beads loaded with a model protein, bovine serum albumin (BSA) were investigated to explore the temporary protection of protein against acidic and enzymatic degradation during gastric passage. Optimum conditions were established for preparation of homogenous, spherical, and smooth chitosan-alginate beads loaded with BSA. Multilayer beads were prepared by additional treatment with either chitosan or alginate or both. The presence of chitosan in the coagulation bath during bead preparation resulted in increased entrapment of BSA. During incubation in simulated gastric fluid (SGF pH 1.2), the beads showed swelling and started to float but did not show any sign of erosion. Inclusion of pepsin in the gastric fluid did not show a further effect on the properties of the beads. Release studies were done in simulated gastric fluid (SGF pH 1.2) and subsequently in simulated intestinal fluid (SIF pH 7.5) to mimic the physiological gastrointestinal conditions. After transfer to intestinal fluid, the beads were found to erode, burst, and release the protein. Microscopic and macroscopic observations confirmed that the release of protein was brought about by the burst of beads. Chitosan-reinforced calcium-alginate beads showed delay in the release of BSA. The multilayer beads disintegrated very slowly. The enzymes pepsin and pancreatin did not change the characteristics of BSA-loaded chitosan-alginate beads. Single layer chitosan-alginate beads released 80-90% of the model protein within 12h while multilayer beads released only 40-50% in the same period of time. The release from chitosan-alginate beads and multilayer beads in SIF was further delayed without prior incubation in SGF. It is concluded that alginate beads reinforced with chitosan offer an excellent perspective for controlled gastrointestinal passage of protein drugs.