Thermally stabilized chondroitin sulfate-hemoglobin nanoparticles and their interaction with bioactive compounds.

The preparation of nanoparticles (NPs) based on hemoglobin (Hb) with a fully biocompatible methodology is presented. The spontaneous formation of electrostatic complexes of Hb with chondroitin sulfate (CS) at pH 4 in the polysaccharide/protein mass ratio regime where charge neutrality is met leads to spherical nanostructures with monomodal hydrodynamic radii distribution in the range of 50-100 nm. The integrity of the electrostatic complexes is disturbed at pH 7 as the net electric charge of Hb is very low. Treating the NPs at mildly elevated temperature stabilizes them against the pH increase taking advantage of Hb's ability of unfolding and self-associating upon thermal treatment. The NPs surface charge is pH-tunable and changes from positive to strongly negative upon pH increase to 7 proving the presence of negative surface patches of Hb and CS segments in their exterior. The α-helix content of Hb does not change significantly by thermal treatment. The NPs are found to bind the bioactive compounds curcumin and ß-carotene and are stable in solutions with high salt content. This investigation introduces a straightforward method to formulate Hb in NPs with possibilities in the nanodelivery of nutrients and drugs.

Protein-induced transformation of unilamellar to multilamellar vesicles triggered by a polysaccharide.

We report on the morphological transitions of didodecyldimethylammonium bromide (DDAB) cationic vesicles and hybrid DDAB/hyaluronic acid (HA) vesicles upon addition of BSA at pH 7 where BSA is overall negatively charged. Small angle neutron scattering (SANS) is used to extract the size distributions of the nanovesicles, the thickness of the DDAB bilayers and their lamellarity. Although the HA-decorated DDAB vesicles contain the negatively charged polysaccharide the interaction with BSA appears to be more intense in comparison to bare vesicles. Characteristic peaks in the SANS patterns indicate the presence of multilamellar interfaces while the formation of multilamellar vesicles induced by BSA depends on the amount of added HA. Consequently, higher lamellarities are observed at higher BSA contents. This work demonstrates a simple methodology to tune the encapsulation of globular proteins in vesicular nanoassemblies by affecting their lamellarity and has direct implications on the application of vesicles and liposomes in protein delivery.