Live/Dead cell viability assay: the L929 mouse fibroblast cells adhered on the previous 12-well plate were rinsed twice with PBS and the cells were stained according to the protocol of the live/dead assay kit (Sigma, 04511-1KT-F). The cells were stained with PBS solution containing 10 μL of calcein-AM and then with 5 μL of propidium iodide (PI) for 30 min at 37 °C. After removing the solution and washing with PBS, the cells were imaged using a fluorescence microscope (Zeiss Observer A1 equipped with AxioCam MRc5) and AxioVision software. The live and dead cells exhibited green and red fluorescence respectively due to calcein-AM and PI.