Formation of a bovine serum albumin diligand complex with rutin and single-walled carbon nanotubes for the reduction of cytotoxicity.

Carbon nanotubes (CNTs) are extensively used in the area of biotechnology and biomedicine, and the binding of proteins to CNTs plays an important role in the potential toxicity of nanomaterials. Rutin is a glycoside of the bioactive quercetin with various health-improving effects due to its antioxidant ability. Demonstration of the interaction between serum albumin and bioactive components is important to design effective carriers for the suppression of CNTs' toxicity. In this study, bindings of bovine serum albumin (BSA) to single-walled CNTs and/or rutin were investigated by fluorescence and molecular docking techniques. The fluorescence of BSA was significantly quenched by both CNTs and rutin in static mode, which was confirmed by the Stern-Volmer calculations. Although rutin showed higher affinity to protein than CNTs, the interactions of both components with BSA did mainly locate within subdomain IIA (site I). BSA-diligand complexes were successfully formed after the simultaneous addition of CNTs and rutin. Bioactive rutin in the BSA-diligand complex still kept strong free radical scavenging activity compared to free rutin or BSA-monoligand complex. Consistently, the cytotoxicity of CNTs and reactive oxygen species formation in endothelial cells was reduced in the BSA-diligand complexes relative to those of BSA-CNTs corona or CNTs alone, where the co-presence of rutin played an important role. These findings suggest the possibility and advantage of designing BSA-based carriers for the suppression of CNTs' toxicity in their biomedical applications.