Antibacterial Activity of Ti₃C₂T_x MXene

MXenes are a family of atomically thin, two-dimensional (2D) transition metal carbides and carbonitrides with many attractive properties. Two-dimensional Ti₃C₂T_x (MXene) has been recently explored for applications in water desalination/purification membranes. A major success indicator for any water treatment membrane is the resistance to biofouling. To validate this and to understand better the health and environmental impacts of the new 2D carbides, we investigated the antibacterial properties of single- and few-layer Ti₃C₂T_x MXene flakes in colloidal solution. The antibacterial properties of Ti₃C₂T_x were tested against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) by using bacterial growth curves based on optical densities (OD) and colonies growth on agar nutritive plates. Ti₃C₂T_x shows a higher antibacterial efficiency toward both Gram-negative E. coli and Gram-positive B. subtilis compared with graphene oxide (GO), which has been widely reported as an antibacterial agent. Concentration dependent antibacterial activity was observed and more than 98% bacterial cell viability loss was found at 200 μg/mL Ti₃C₂T_x for both bacterial cells within 4 h of exposure, as confirmed by colony forming unit (CFU) and regrowth curve. Antibacterial mechanism investigation by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with lactate dehydrogenase (LDH) release assay indicated the damage to the cell membrane, which resulted in release of cytoplasmic materials from the bacterial cells. Reactive oxygen species (ROS) dependent and independent stress induction by Ti₃C₂T_x was investigated in two separate abiotic assays. MXenes are expected to be resistant to biofouling and offer bactericidal properties.