Scientific article: Some blood proteins always stick

The fate of nanoparticles in a biological system is determined by their protein corona, as remodeling of their surface properties through protein adsorption triggers specific recognition such as cell uptake and immune system clearance and nonspecific processes such as aggregation and precipitation. Using the most sensitive measurements so far, we demonstrate that state-of-the-art biomedical nanoparticles get tagged by sticky marker proteins in the blood.

The state-of-the-art design of biomedical nanoparticles is the core−shell structure exemplified by superparamagnetic iron oxide nanoparticles (SPIONs) grafted with dense, well-hydrated polymer shells used for biomedical magnetic imaging and therapy.

Densely grafted polymer chains form a polymer brush, yielding a highly repulsive barrier to forming a protein corona via nonspecific particle−protein interactions. However, recent studies showed that the abundant blood serum protein albumin interacts with dense polymer brush-grafted SPIONs.

We used isothermal titration calorimetry to characterize the interactions between human serum albumin, human serum immunoglobulin G, human transferrin, and hen egg lysozyme with polymer-grafted SPIONs with different grafting densities and core sizes. This set of proteins represent important proteins in the blood that can alter nanoparticle properties and mediate their biological interactions.

The two investigated SPIONs show similar protein interactions despite their different “stealth” capabilities in cell culture. They resist attractive interactions with lysozymes and transferrins. However, they both show significant binding of albumin and immunoglobulin G.

Our results highlight that protein size, flexibility, and charge are essential to predict protein corona formation on polymer brush-stabilized nanoparticles. The study is published in ACS Applied Bio Materials as “Polymer Brush-Grafted Nanoparticles Preferentially Interact with Opsonins and Albumin”.