Influences of protein-corona on stability and aggregation kinetics of Ti3C2Tx nanosheets in aquatic environment.

Proteins existed in aquatic environments strongly influence the transport, fate of nanomaterials due to the formation of protein-corona surrounding nanomaterials. To date, how do proteins affect the aggregation behaviors of MXene, a new family of two-dimensional materials, in aquatic environment remains unknown. Here the aggregation kinetics of MXene Ti3C2Tx nanosheets in various electrolytes (NaCl, CaCl2 and Na2SO4) was investigated by time-resolved dynamic light scattering in absence or presence of bovine serum albumin (BSA). Results showed that BSA affected the aggregation of Ti3C2Tx in a concentration-dependent manner. Addition of 3 mg/L BSA decreased the critical coagulation concentrations (CCCs) of Ti3C2Tx about 1.6-2.1 times, showing obvious destabilization effect; while BSA greater than 30 mg/L created a high-protein environment covering Ti3C2Tx, producing high spatial repulsion and enhancing the dispersibility of Ti3C2Tx. Ca2+ ions have greater effect on the aggregation of Ti3C2Tx due to the larger surface charge and bridging effect. The interaction between Ti3C2Tx and BSA followed Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, and mainly attributed to hydrogen bonding and van der Waals forces, while positively charged lysine and arginine in BSA might attract onto Ti3C2Tx through electrostatic attraction. The interaction decreased the content of α-helix structure in BSA from 74.7% to 53.1%. Ti3C2Tx easily suffered from aggregation and their long-distance transport seemed impossible in synthetic or natural waters. The present findings provided new insights for understanding the transfer and fate of this nanomaterial in aquatic environments.

Investigation of interaction between MXene nanosheets and human plasma and protein corona composition.

The composition of protein corona affects the behavior and fate of nanoparticles in biological systems, which strongly relates to the intrinsic properties of nanoparticles and proteins. Here, three types of MXene Ti3C2Tx nanosheets are prepared by different etching methods, and certain physicochemical characteristics of the nanosheets before and after exposure to human plasma (HP) are characterized. The Ti3C2Tx nanosheets with protein coronas suffer more easily from aggregation than pristine Ti3C2Tx. The composition of protein coronas by LC-MS/MS-based label-free proteomic analysis reveals a high overlap of protein types and functions but a significant difference in relative protein abundance for the three Ti3C2Tx. Immunoglobulins and coagulation proteins are highly enriched while albumin is depleted in the coronas compared with their abundance in original HP. The random forest classification model predicts that the main driving forces for the adsorption of HP proteins on Ti3C2Tx are hydrogen bonding, steric hindrance, and hydrophobic interaction. This study provides insights into the colloidal stability of Ti3C2Tx nanosheets and their interaction with human plasma proteins.