Gold and silver nanoparticle interactions with human proteins: impact and implications in biocorona formation

The role of nanoparticle (NP) interaction with biomolecules to form a biomolecular corona is the key to NP behavior and its consequences in the physiological environment. Since the adsorbed biocorona decides the fate of a nanomaterial in vivo, and thus its successful application in the biomedical arena, a comprehensive understanding of the dynamic interactions of the proteins with the NP is imperative. A systematic investigation on time dependent adsorption kinetics and individual protein corona formation was conducted with citrate and lipoic acid coated 40 nm sized gold NP (AuNP) and silver NP (AgNP). Both NP were exposed to three major human hard corona proteins; human serum albumin (HSA) (40 mg ml^-1), fibrinogen (2 mg ml^-1) and immunoglobulin G (IgG) (12 mg ml^-1) at their physiological concentrations for 24 h. Time evolution data over 0, 6, 12 and 24 h revealed that irrespective of surface chemistry, rapid and prominent binding of HSA and IgG formed coronas over both citrate and lipoic acid coated Au and AgNP causing an increase in size, without agglomeration up to 24 h at 37 °C. In contrast, fibrinogen triggered agglomeration instantaneously upon contact with NP. These findings suggest that irrespective of NP surface chemistry or chemical composition, corona proteins at their physiological concentrations interact rather differently; wherein HSA and IgG coronas adsorbed strongly on the NP surface and kept both Au and AgNP well dispersed, while fibrinogen caused rapid, strong and irreversible agglomeration. Remarkably, individual protein coronas were observed to confer varied cellular uptake patterns for NP-protein complexes in human endothelial cells wherein HSA and IgG coronas showed higher cellular uptake compared to the fibrinogen corona.