Basic principles of in vivo distribution, toxicity, and degradation of prospective inorganic nanoparticles for imaging

Abstract

Iron oxide, gold, and silver nanoparticles, together with quantum dots, represent the salient inorganic nanoparticles that have been considered as prospective imaging agents. Characterized by specific chemical composition and material-specific in vivo fate, they represent distinct features, going from highly biocompatible and biodegradable to apprehensively toxic, biostatic, or particularly inert, respectively. While questions on inorganic nanoparticle behavior still remain, their in vivo fate starts to refine and their interactions with biomolecules, cells, and organs appear to converge to a certain extent. In order to be injected to living organisms, these particles have to be stabilized by a coating, which subsequently interacts with biomolecules, including proteins, influences particles’ behavior, and eventually strips off. Then, within cellular compartments, mainly in liver and spleen, particles aggregate. This generally impacts particles’ imaging functionality, which further deteriorates when biomolecules interact and the process of particles’ degradation commences. While the rates of particles’ decay intrinsically differ and their biological pathways diverge, the mechanisms of their potential toxicity remain similar and are mainly due to the generation of reactive oxygen species. Nevertheless, at some point, the organism seems to manage these nanoparticles and gradually eliminates them from the body.