Stability optimization of orthovanadate nanoparticles in biocompatible media

Rare-earth orthovanadate nanoparticles (NPs) demonstrate unique combination of physicochemical characteristics and biological activity. The redox properties and low toxicity of orthovanadates in nanoform allow considering them as perspective nanomedicine modalities. The local microenvironment in biological media and the way NPs enter the organism determine their biological efficiency. Numerous studies deal with interaction of vanadium species and bio-molecules in serum, however, the interplay between orthovanadate NPs and serum compounds is still under debates. Here we investigate the effect of serum proteins on aggregative stability of three types of negatively charged orthovanadate NPs (spherical, spindle-like, and rod-like). Size of NPs was estimated by light-scattering methods in solutions, biologically relevant buffers and media. Some geometry- and size-dependent peculiarities of NPs behavior in different solutions were found. Modeling the proteins–NPs interactions for main serum proteins at threshold Ca²⁺ and Mg²⁺ concentrations revealed nonlinear aggregative behavior depending on protein concentrations. In Krebs-Ringer buffer the behavior of the rod-like NPs differs strongly on the behavior of more isometric NPs (spherical and spindle-like). The hydrodynamic diameter changes are non-linear and rod-like NPs have specific behavior in serum-like protein mixtures. These effects are associated with shape-specific involvement of different forces (including electosteric, hydrophobic, osmotic and recoil ones) in stabilization process.