A simple, low-cost and green method for controlling the cytotoxicity of MXenes.

MXene phases are a member of the intriguing 2D material family, beyond graphene. They are good candidates for many applications, however, their potential toxicity is of crucial importance for future development. Herein, we present a simple, low-cost and fully green approach for controlling the potential cytotoxicity of 2D MXenes after delamination by harnessing the interactions that occur between the surface of MXene phases and natural biomacromolecule - collagen. We also demonstrate that the step-by-step adsorption and desorption of collagen from the surface of 2D MXenes is easily controlled using in situ zeta potential measurements coupled with dynamic light scattering (DLS) method. The obtained results demonstrated that the electrostatically driven unprecedented susceptibility of the MXenes' surfaces to collagen. Surface-modification reduces toxicity of MXenes in vitro i.e. adjust cells' viabilities as well as reduce their oxidative stress. This indicates enhanced biocompatibility of 2D Ti3C2 and Ti2C MXenes surface-modified with collagen, which is involved in many bio-interactions as important building blocks in the human body. The presented study opens new avenues for designing MXenes with defined surface properties and paves the way for their future successful management in nano-medicinal applications.

Multilayered stable 2D nano-sheets of Ti2NTx MXene: synthesis, characterization, and anticancer activity.

BACKGROUND: The biological activity of MXenes has been studied for several years because of their potential biomedical applications; however, investigations have so far been limited to 2D titanium carbides. Although monolayered Ti2NTx MXene has been expected to have biological activity, experimental studies revealed significant difficulties due to obstacles to its synthesis, its low stability and its susceptibility to oxidation and decomposition. RESULTS: In this paper, we report our theoretical calculations showing the higher likelihood of forming multilayered Ti2NTx structures during the preparation process in comparison to single-layered structures. As a result of our experimental work, we successfully synthesized multilayered Ti2NTx MXene that was suitable for biological studies by the etching of the Ti2AlN MAX phase and further delamination. The biocompatibility of Ti2NTx MXene was evaluated in vitro towards human skin malignant melanoma cells, human immortalized keratinocytes, human breast cancer cells, and normal human mammary epithelial cells. Additionally, the potential mode of action of 2D Ti2NTx was investigated using reactive oxygen tests as well as SEM observations. Our results indicated that multilayered 2D sheets of Ti2NTx showed higher toxicity towards cancerous cell lines in comparison to normal ones. The decrease in cell viabilities was dose-dependent. The generation of reactive oxygen species as well as the internalization of the 2D sheets play a decisive role in the mechanisms of toxicity. CONCLUSIONS: We have shown that 2D Ti2NTx in the form of multilayered nanoflakes exhibits fair stability and can be used for in vitro studies. These results show promise for its future applications in biotechnology and nanomedicine.

Influence of modification of Ti3C2 MXene with ceramic oxide and noble metal nanoparticles on its antimicrobial properties and ecotoxicity towards selected algae and higher plants.

The number of investigations regarding the application of 2D nanosheets of MXenes in different technological areas is growing rapidly. Different surface modifications of MXenes have been introduced to date in order to tailor their properties. As a result, surface-modified MXenes could be released in the environment from filtration membranes, adsorbents, or photocatalysts. On the other hand, assessment of their environmental impact is practically unexplored. In the present study, we examined how modification of the antimicrobial Ti3C2 MXene with ceramic oxide and noble metal nanoparticles affects its toxic behavior. The expanded 2D sheets of the Ti3C2 MXene phase were modified with Al2O3/Ag, SiO2/Ag, and SiO2/Pd nanoparticles using the sol-gel method and extensively characterized. The obtained 2D nanocomposite structures were characterized by antibacterial properties. The ecotoxicological assays considered green algae (Desmodesmus quadricauda) as well as two higher plants: sorghum (Sorghum saccharatum) and charlock (Sinapis alba). Our results revealed that obtained nanomaterials can cause both stimulating and inhibiting effects towards algae, and the ecotoxicity depended on the concentration and the type of modification. The study reveals the intriguing property of pristine Ti3C2 which highly stimulated green algae growth at low concentrations. It also shows that modification of pristine Ti3C2 MXene with different nanoparticles changes the ecotoxicological effects of the resulting nanocomposite 2D structures. We have also indicated nanocomposite structures that does not revealed the toxic effect on tested organisms i.e. the Ti3C2 MXene surface-modified with Al2O3/Ag was not phyto- and eco-toxic. This work helps with better understanding of the reactivity of surface-modified MXenes towards chosen organisms, giving more information concerning the potential impact of tested nanocomposites on the ecosystems.

In vitro studies on cytotoxicity of delaminated Ti3C2 MXene.

MXenes are a novel family of 2D materials, the biological activity of which has been largely unexplored. The present study, for the first time, shows some aspects of the in vitro toxicity of 2D sheets of Ti3C2 MXene. The Ti3AlC2 MAX phase was used in an expansion and delamination process to obtain Ti3C2 material in the form of 2D sheets. The obtained 2D material was characterized using SEM, TEM, DLS, XPS, and zeta potential. The biological activity of the MXene was determined on two normal (MRC-5 and HaCaT) and two cancerous (A549 and A375) cell lines. The cytotoxicity results indicated that the observed toxic effects were higher against cancerous cells compared to normal ones. The mechanisms of potential toxicity were also elucidated. It was shown that MXene may affect the occurrence of oxidative stress and, in consequence, the generation of reactive oxygen species (ROS). The results of the present study provide the principal knowledge to date regarding the biological activity of the MXenes; the lack of such knowledge is the major obstacle on the MXenes' road to further research and development on their applications in bioscience and biotechnology, e.g. as drug-delivery systems.