The reactivity (and potential risks) posed by inorganic nanoparticles in biological environments depends on their physical and chemical state. Biological fluids such as blood, mucus, cell culture media, and others contain a large variety of substances that can interact with and modify nanoparticles. The nanoparticle protein corona, the outcome of the absorption of proteins onto the inorganic surface, is one of the most significant alterations. This coating provides a "biological identity" to nanoparticles in those fluids and determines their interaction with cells, immune systems and other components of biological systems.
As a result, detailed knowledge of the nanoparticle protein corona has emerged as a crucial aspect in understanding the biodistribution and reactivity of nanoparticles in organisms and, therefore, for the safe design of the engineered nanoparticles.
As reported in Small, Dr. Eudald Casals and ICREA Prof. Victor Puntes of the ICN, along with their colleagues in the University of Salzburg, studied the surface modifications of metal (Au, Ag) and metal oxide (Fe3O4, CeO2 and CoO) nanoparticles with sizes ranging from 7 to 20 nm dispersed in commonly used cell culture medium supplemented with serum. All tested nanoparticles absorb proteins onto their surface, thereby forming a protein corona through a dynamic process evolving towards an irreversible coating (hard protein corona).
Despite the fact that the studied nanomaterials have similar characteristics of hydrophobicity and surface charge, different temporal patterns of the protein corona formation were observed that can be considered a fingerprint for nanoparticle identification. Moreover, the researchers found that the protein corona formation on CoO nanoparticles reduces their adverse effects on cellular oxidative stress.