Cell migration is crucial for many physiological and pathological process. Following the lung injury, proliferation and migration of lung epithelial cells to the epithelial lining of alveoli and airways in the lung are pivotal for remodeling and repair of the wound to restore normal lung function. In the present study, we examined the modulatory effect of carboxylated nanodiamonds (cNDs) on the cell division, migration, and adhesion of epithelial cells in the well-established in vitro model of wound repair and cell migration. Flow cytometry and confocal microscopy results indicated that both LA4 and A549 cells effectively internalized fluorescent carboxylated nanodiamonds (cFNDs) and the internalized nanodiamonds were essentially localized in the cytoplasmic region. Treatment with cNDs blocked the division and migration of cells to fill the scratch wound. Live cell imaging and time-lapse videography of the wound healing process indicated a significant inhibition of cell proliferation activity in cND-treated cells and blocked the wound repair process. Trans-well cell-migration assay results further support the inhibitory effect of cNDs on the cell migration process. Western blotting and immunofluorescence staining indicated that the crucial proteins involved in epithelial-mesenchymal transition (EMT) and cell migration i.e. β-catenin, Vimentin, NM-myosin, and Focal Adhesion Kinase (FAK) were downregulated after treatment with cNDs, while the expression of E-cadherin and Claudin-1, major cell adhesion markers remained unaltered. Taken together, our results indicate that the decline in cell proliferation activity, downregulation in the expression of various crucial protein like β-Catenin, NM-myosin, FAK, and Vimentin involved in the cell migration and unaltered expression of cell adhesion molecules E-cadherin and Claudin-1, may be the factors that contribute to the cND-mediated inhibition of EMT during the wound repair process in the monolayers of lung epithelial cells. These results provide an insight into the effect of nanodiamonds on several crucial parameters of EMT and migration of lung epithelial cells. Loss of cell-to-cell adhesion followed by migration are also the factors that facilitate the metastasis of cancer cells. Demonstration that the nanodiamonds can inhibit these cellular properties may also open up the possibility of exploring the use of nanodiamonds as a potential candidate in cancer therapy.

Dr. Sushreesangita P Behera, a doctoral candidate working under the supervision of Prof. Rajiv K Saxena at South Asian University, India. Her work is mainly focus on the modulation of cell adhesion and migration by carbon nanoparticles in lung epithelial cells. Additionally we are also focussing on lung injury model and tumor metastatic model in the mice.