Probing the glycans accessibility in the nanoparticle biomolecular corona

Hypothesis: Following blood administration, the pristine surface of nanoparticles (NPs) associates with biomolecules from the surrounding environment forming the so-called "biomolecular corona". It is well accepted that the biomolecular corona dramatically affects the NP fate in the biological medium while the pristine surface is no longer available for binding. Recent studies have shown that the glycans associated with the proteins forming the corona have a role in the NP interaction with macrophages, but the glycan identities remain unknown. We aim here to identify the glycan composition of the biomolecular corona and to assess the role of these glycans in the interaction of the proteins from the corona with glycan binding biomolecules, such as lectins.

Experiments: In this study, we have characterized the biomolecular corona of citrate stabilised gold NPs after exposure of the NPs to blood plasma at two different plasma concentrations, mimicking the in vitro and in vivo conditions. We have extensively characterized the biomolecular corona using HILIC chromatography and shotgun proteomics. Following this, a lectin binding assay was carried out using Dynamic Light Scattering (DLS) and Fluorescence Correlation Spectroscopy (FCS) to assess whether proteins with known affinity towards specific glycans would bind to the corona.

Findings: Our findings highlighted that the protein corona composition is dependent on the exposing conditions. However, under both plasma concentrations, the biantennary sialylated glycans (A2G2S2) are enriched. DLS and FCS confirmed that the glycans are accessible for binding as the corona interacts with lectins with known affinity towards terminal sialic acids and the enzymatic removal of the glycans leads to a decrease in lectin affinity. This study shows for the first time that the glycans are present in the corona and that they could potentially be responsible for the modulation of NP biological processes as they can directly engage with glycan binding receptors that are highly expressed in an organism.