Interactions of cationic gold nanoclusters with serum proteins and effects on their cellular responses

Cationic nanoparticles (NPs) have shown great potential in biological applications owing to their distinct features such as favorable cellular internalization and easy binding to biomolecules. However, our current knowledge of cationic NPs' biological behavior, i.e., NP-protein interactions, is still rather limited. Herein, we choose ultrasmall-sized fluorescent gold nanoclusters (AuNCs) coated by (11mercaptoundecyl) - N, N, N - trimethylammonium bromide (MUTAB) as representative cationic NPs, and systematically study their interactions with different serum proteins at nano-bio interfaces. By monitoring the fluorescence intensity of MUTAB-AuNCs, all proteins are observed to bind with roughly micromolar affinities to AuNCs and quench their fluorescence. Transient fluorescence spectroscopy, X-ray photoelectron spectroscopy and isothermal titration calorimetry are also adopted to characterize the physicochemical properties of MUTAB-AuNCs after the protein adsorption. Concomitantly, circular dichroism spectroscopy reveals that cationic AuNCs can exert protein-dependent conformational changes of these serum proteins. Moreover, protein adsorption onto cationic AuNCs can significantly influence their cellular responses such as cytotoxicity and uptake efficiency. These results provide important knowledge towards understanding the biological behaviors of cationic nanoparticles, which will be help- ful in further designing and utilizing them for safe and efficient biomedical applications. (c) 2021 Elsevier Inc. All rights reserved.

Automated summary

This study systematically investigates the interactions between cationic nanoparticles and different serum proteins at nano-bio interfaces. The experimental results show that proteins bind to AuNCs with micromolar affinities and quench their fluorescence; protein adsorption onto cationic AuNCs significantly influences their cellular responses.