Proteins adsorbed to gold nanoparticles (AuNPs) form bioconjugates and are critical to many emerging technologies for drug delivery, diagnostics, imaging, and other biomedical applications. A robust interaction between the immobilized protein and AuNP is essential for the bioconjugate to perform as designed. Thus, extensive effort to understand protein-AuNP interaction is necessary. Recently, our group demonstrated that IgG has a stronger adsorption affinity to AuNPs than many other abundant blood proteins, and we attributed this high affinity to the number of free thiols displayed by IgG. Here we explore a potential correlation between the number of free thiols groups present in a protein and the protein-AuNP adsorption affinity. In this study, human serum albumin (HSA) was chemically modified to introduce additional free thiols using Traut’s reagent. We quantified the displacement of unmodified and thiol-modified HSA analogs adsorbed on AuNPs by IgG using complementary analytical techniques, such as dynamic light scattering (DLS), inductively coupled plasma optical emission spectrometry (ICP-OES), UV-vis spectrophotometry, and an enzyme mediated assay. We found that HSA displacement from the AuNP correlated with the experimentally measured number of accessible free thiol groups. This work provides a pathway to control the number of free thiols on a protein to facilitate the synthesis of a robust bioconjugate capable of surviving a complex biological environment.

Systematic control of thiol groups on proteins for manipulating interaction with gold nanoparticles

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.