Mineralogical and physicochemical characterization of the Pb and magnetite interaction in a simulated biofluid

In human beings, metals have a role in biochemical and physiological functions, but an excess of metals concentration and consequent precipitation can result in adverse effects, triggering a variety of diseases.

In particular, Pb is a metal known to damage several organs in the body, and the literature emphasizes its effects on the central nervous system. Lead disrupts important mechanisms of neural systems, such as synapse formation, axon dendritic extension, and plasticity.

Moreover, other studies focus on the presence of both endogenous and exogenous magnetite in the human brain, which might preferentially adsorb Pb.

In this study, we investigate the interaction between Pb, in the form of Pb(NO₃)₂ , and magnetite nanoparticles smaller than 200 nm, as this isthe dimension that allows particles to pass through the blood brain barrier. This investigation focusses on a low-temperature and low-pressure environment, mimicking the human brain condition by means of a simulated biofluid (a phosphate buffer saline – PBS). Our goal is to understand the nanoparticles physicochemical state pre- and post-interaction, the Pb and Fe valence state at the magnetite surface or near-surface, and the adsorption capacity of such ions (Pb) by magnetite.

The experiment was performed by adding to a PBS suspension of magnetite nanoparticles, PBS previously mixed with Pb(NO₃)₂. The solution was kept at 39°C for 48h, rinsed with distilled water, and the solid phase was prepared for the following analyses.

The samples pre- and post-interaction were characterized using a multi-analytical approach combining PXRD, XPS, SEM-EDXS and TEM-EDXS. It has been observed that magnetite adsorbs Pb on its surface through the complexation of Pb with deprotonated surface hydroxyl groups, whichare critical functional groups.