Rheological characterization and physical-stability of gamma irradiated anthocyanin-loaded albumin nanoparticles

The active blueberry compounds called anthocyanins have poor oxidation stability, but, if encapsulated by protein nanoparticles, they can be protected due to the slowing down of the oxidation process. This work describes the advantages of using a γ-irradiated bovine serum albumin nanoparticle bound to anthocyanins. The interaction was characterized biophysically, mainly by rheology. By computational calculation and simulation based on model nanoparticles, we estimated the number of molecules forming to the albumin nanoparticles, which allowed us to infer a ratio of anthocyanin/nanoparticles. Measurements by UV-VIS spectroscopy, FT-IR spectroscopy, fluorescence spectroscopy, dynamic light scattering (DLS), ζ potential, electron transmission microscopy and rheology at room (25 °C), and physiological (37 °C) temperatures were performed. The spectroscopy measurements allowed identifying additional hydrophobic sites created during the irradiation process of the nanoparticle. Based on the rheological studies, it was observed that for all the temperatures selected, the BSA-NP trend is a Newtonian flow behavior type, and there is a direct correlation between dynamic viscosity and temperature values. Furthermore, when anthocyanins are added, the system increases its resistance to the flow reflected in the morphological changes observed by TEM, confirming the relationship between viscosity values and aggregate formation