Antibody-gold nanoparticle (AuNP) conjugates are central to many emerging nanobiotechnology applications. Immobilization of the antibody on the AuNP surface to provide a robust interaction, facilitate colloidal stability, and provide proper orientation of the antibody is critical to realize the potential benefits of these novel platforms. Recent studies have demonstrated that localized regions of charge on the antibody are responsible for the orientation of the immobilized protein. In this presentation, we will describe efforts to modulate the surface charge of an antibody using solution pH and measure the impact of protein charge on adsorption. The adsorption affinity between the antibody and AuNP was extracted from adsorption isotherms generated via nanoparticle tracking analysis (NTA) and was found to be independent of the protein charge. However, differences in the measured thickness of the protein layer suggest that protein charge impacts the orientation of the immobilized antibody. An enzyme-mediated assay was developed to confirm pH-dependent orientation. Adsorption dynamics of ubiquitous plasma proteins to AuNPs were also analyzed and compared to antibody adsorption. The antibody displayed the greatest affinity for the AuNP among the tested plasma proteins. Moreover, the enzyme-mediated assay confirmed that antibody irreversibly adsorbed to AuNPs and resisted displacement under the stress of a physiological environment. This work provides additional insight into the mechanism of antibody adsorption and better defines the capabilities and potential limitations of antibody-AuNP conjugates in emerging bioanalytical technologies.

Investigating the stability and orientation of antibody adsorbed onto gold nanoparticles

ACS Spring Meeting 2021

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