Investigate the interaction of nanomaterials with biological systems, known as nano-bio interaction is of great interest for the assessment of the concern arising from nanomaterials progressive use. Such interaction determines nanomaterials potential effect on human and environment becomes more and more important to understand how they interact with living organisms and the environment. The novel physicochemical characteristics of nanomaterials, such as their small size, large surface area to volume ratio and surface energy, may initiate new toxicological effects due to nanomaterials ability to enter into the biological systems through adsorption and dissolution and modify the structure of various macromolecules An example of these interactions is the adsorption of proteins on nanoparticles surface forming what is known as the 'protein corona'. Therefore, being able to understand how these molecules and other biologically important species are adsorbed and interact, should help us to reduce any adverse impacts of nanoparticles on human health and the environment.
Due to the importance of surface composition and surface functionality in nanotoxicology, analytical tools that can probe the change in the structure and composition of the nanoparticles in aqueous media are crucial but remain limited. Therefore in this work, in situ characterization of the liquid–solid interface to probe surface adsorption of environmentally and biologically relevant media on nanoparticle surfaces has been conducted. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy provides the molecular information that allows for the determination of the adsorption mode such as conformational and structural changes of the coordinating ligand. Surface adsorption of titanium dioxide (TiO2) nanoparticles have been investigated in different biological media typically used for toxicity studies and show that the surface composition of TiO2 nanoparticles depends to a large extent on the composition of the medium due to surface adsorption. Moreover, hydrodynamic diameter and surface charge of TiO2 NPs were evaluated using dynamic light scattering DLS. The results indicated that TiO2 NPs undergo different trends in aggregation upon the adsorption of biological media on its surface and zeta potential measurements showed surface charge alterations which are consistent with the aggregation study.
In order to understand the dynamic transformations of nanomaterials in biological environments, the effect of dissolution has been predicted. Copper oxide CuO and zinc oxide ZnO nanoparticles were used to study dissolution due to their instability in biological media. Once these particles exposed to solutions they release their ions and tend to aggregate. Therefore, the dissolution of these materials was conducted at size ca. 24 nm and nanoparticles coated with proteins and humic acid employing simulated lung fluids as models to develop a better understanding of how these properties effect the solubility and stability in biological systems. From this study, it was found that both copper oxide and zinc oxide NPs showed different trends in dissolution. Cu and Zn ions once coated with proteins and HA highly dissolved in ALF at low pH 4.5 compared with other fluids (Gamble’s solution and water) at extracellular pH which shows only slightly enhanced in the basal condition. The acidity of ALF may explain the higher solubility of metals that are phagocytized versus those that remain extracellular. Some general conclusions can be drawn from these investigations. It seems that analytical tools to characterize the interfacial region between nanopaerticles and these complex systems provide a reasonably good qualitative and quantitative description of the interactions.