Adsorption of human serum albumin on functionalized single-walled carbon nanotubes reduced cytotoxicity

With the potential uses of carbon nanotubes (CNTs) in biomedical and biotechnological applications, and the growing concerns about nanotoxicity of these engineered nanoparticles, the importance of protein-nanoparticle interaction has not been well stressed. In this study, we used both experimental and theoretical approaches to investigate the interactions of different functionalized single-walled CNTs (SWCNTs) with human serum albumin (HSA). It was found that the HSA adsorption capacities of CNTs followed the order carboxylated SWCNTs > hydroxylated SWCNTs > amined SWCNTs. The fluorescence intensity of HSA was quenched by all of the three SWCNTs in static mode, which was authenticated by Stern-Volmer calculations. Our molecular dynamics simulations revealed that both atom-atom contact numbers and binding energies between functionalized SWCNTs and HSA played critical roles in determining their adsorption capacity, in agreement with the experimental findings. Additional cytotoxicity assays revealed that coating of carboxylated CNTs with HSA more significantly reduced their cytotoxicity than the other two CNTs, in agreement with their protein adsorption capacities in vitro. These findings will be helpful to clarify the mechanism of interactions of functionalized SWCNTs with human serum proteins, and provide more insight into the understanding of how to design the safe nanoparticles by preconsideration of their interactions with proteins.