A quantitative binding study of fibrinogen and human serum albumin to metal oxide nanoparticles by surface plasmon resonance

The interaction of plasma proteins with metal oxide nanoparticles (NPs) is important due to the potential biomedical application of these NPs. In this study, new approaches were applied to measure quantitatively the kinetics and affinities of fibrinogen and human serum albumin (HSA) for TiO2, CeO2, Al2O3 and ZnO NPs immobilized on a sensor chip. Real-time surface plasmon resonance (SPR) measurements showed that fibrinogen interacted with TiO2 and CeO2 NPs with high affinity (135 and 40 pM, respectively) and to Al2O3 NPs with moderate affinity (15 nM). The data fitted well to the Langmuir model describing a 1:1 interaction. In contrast, HSA interacted with TiO2, CeO2 and Al2O3 NPs with lower affinity (80 nM, 37 nM and 2 µM, respectively) with the data fitting better to the conformational change model. TiO2 and CeO2 NPs had fast association rate constants with fibrinogen (1×106 M−1 s−1) and Al2O3 NPs had a slower association rate constant (1×104 M−1 s−1). By contrast, HSA had markedly slower association rate constants (1×103-1×104 M−1 s−1). The binding of the proteins was reversible, thus allowing the rapid capture of data for replicates. The occurrence of matrix effects was evaluated by using surfaces with different chemistries to capture the NPs, namely alginate, NeutrAvidin and bare gold. The affinity values determined for the NP-protein interactions were largely independent of the underlying surface used to capture the NPs.