Study on two-dimensional semiconducting material based nanocomposite film for transparent antibacterial applications

Abstract

Two-dimensional (2D) nanomaterials, such as graphene-based materials and transition metal dichalcogenide (TMD) nanosheets, are promising materials for biomedical applications owing to their remarkable cytotoxicity and physicochemical properties. Based on their potent antibacterial properties, 2D materials have potential as antibacterial films, wherein the 2D nanosheets are immobilized on the surface and the bacteria may contact with the basal planes of 2D nanosheets dominantly rather than contact with the sharp edges of nanosheets. However, there are lack of studies on antimicrobial properties of 2D nanosheet surface while research groups mostly take into account the bacterial interaction with 2D nanosheets in a dispersed form. To address these points, in this study, we prepared an effective antibacterial surface consisting of representative 2D materials, i.e., graphene oxide (GO) and molybdenum disulfide $(MoS_2)$, formed into nanosheets on a transparent substrate for real device applications. The antimicrobial properties of the $GO-MoS_2$ nanocomposite surface toward the Gram negative bacteria Escherichia coli were investigated, and the $GO-MoS_2$ nanocomposite exhibited enhanced antimicrobial effects with increased glutathione oxidation capacity and partial conductivity. Furthermore, direct imaging of continuous morphological destruction in the individual bacterial cells having contacts with the $GO-MoS_2$ nanocomposite surface were characterized by holotomographic (HT) microscopy, which could be used to detect the refractive index (RI) distribution of each voxel in bacterial cell and reconstruct the three-dimensional (3D) mapping images of bacteria. In this regard, both the decreases in the volume (~67.21%) and dry mass (~78.75%) of bacterial cells came in contact with the surface for 80 min were quantitatively measured, and releasing of intracellular components mediated by membrane and oxidative stress was observed. Our findings provided new tools for label-free real-time tracing of bacterial cell with which to improve our understanding of antimicrobial activity, and opened a window for the 2D nanocomposite as a practical antibacterial film in biomedical applications.