A. Palumbo, F. Tourlomousis, R. Chang, E.H. Yang
Stevens Institute of Technology,
Keywords: transition metal dichalcogenides, cell-substrate interactions, fibroblast cells, cell adhesion, morphometry
Summary:Transition metal dichalcogenides (TMDs), such as WS2 and MoS2, have been widely explored for their utilization as two-dimensional (2D) semiconducting nanomaterials with unique electronic, mechanical, and catalytic properties. A multitude of research has been pursued to integrate these unique properties of TMDs into a diversity of biomedical applications, including drug delivery, therapeutics, biosensors and bio-imaging. Although cytotoxicity studies have been performed on TMDs [1-6], cell-substrate interactions of TMDs are not well reported in literature and require further study to illuminate the influence of TMDs on the adhesive interactions of biological cells and the subsequent incorporation of these nanomaterials for potential biological applications. In this work, WS2 and MoS2 are grown via chemical vapor deposition (CVD) on SiO2 substrates and seeded with human fibroblast cells at cell densities of 15,000 cells/cm2. Cell culture is similarly performed on SiO2 substrates without TMD, as TMD-free control samples to compare the effects of TMD presence on the adherence of fibroblast cells. After culturing, the cell-substrate interactions are probed after 24 hours using a methyl violet staining. To perform dimensional metrology and analysis, optical microscope images were collected and postprocessed using thresholding and noise filtering algorithms in order to segment individual cell bodies (n = 50-60 cells/sample). Cells that were either in contact with other cells or not fully in the field of view were discarded from analysis. Cellular morphometric features (cell area, eccentricity) were computed from the segmented cell outlines. Upon determination of the corresponding mean and standard deviation values, unpaired t-tests were performed on the mean values of cell area and eccentricity, whereas F-tests were performed on the variances, as shown in Figure 1. It was observed that the presence of TMDs improves the cellular adhesion and viability on the cytotoxic SiO2 substrate. Cells adhered on SiO2 were significantly smaller and more eccentric than those in the presence of TMDs, confirming this observation; furthermore, cell morphology was determined to be more elongated on MoS2 than WS2. Though there was no significant difference determined between the mean cell area between MoS2 and WS2, statistical significance was determined for their variances, indicating a significantly larger range of cell areas for the WS2 sample. Current experiments being performed include cell culturing on patterned TMDs grown in controlled arrays. TMD patterns only on predefined locations are created via photolithography on a SiO2 substrate and subsequent lift-off followed by physical vapor deposition (PVD) of MoO3 or WO3 prior to CVD growth. Thus, cell-substrate interactions between biological cells and TMDs will be quantitatively analyzed in relation to differing TMD area of coverage, layers, and porosity to probe the causal relationship between the measured TMD substrate properties and cell attachment.