Fig. 1: FESEM images of type 1 collagen fibrils with different concentrations created on 1-hexadecanethiol-treated IDEs; (A) 1000\(\mu g/mL\) , (B) 500 \(\mu g/mL\), (C) 250 \(\mu g/mL\).
Cell culture on collagen thin films
The MSCs, HUVEC, and MDA-MB-231 cell lines were bought from the National Cell Bank of Iran (Pasteur Institute, Iran). They were cultured in Dulbecco’s modified Eagle’s medium (DMEM) (Mediatech, Herndon, VA) supplemented with 10% fetal bovine serum (FBS; Gibco Invitrogen, Carlsbad, CA) and 1% penicillin/streptomycin (Gibco). Before seeding cells on the alkanethiol-treated electrodes containing collagen thin films, the thin films were covered in DMEM medium with 5% FBS at least for 3 h three times. This step was required to normalize the collagen thin film concerning likely absorption of serum proteins[3]. Cells were detached from culture plates by trypsinization, rinsed with DMEM culture medium having 5% FBS, and then centrifuged for 3 minutes at 1000 rpm. Then, the suspended cells in DMEM medium with 5% FBS covered on the thin films of collagen at a 2\(\times 10^{4}\) cells/cm2 density and held at 37 °C for 48 h. The decreased concentrations of serum maximizes the amount of cell signaling owning to the extracellular matrix[3]. Fig. 2 (C-D) shows the microscopic images of MSCs and HUVEC cells on collagen thin films with various concentrations.
Impedance measurements
Impedance measurements of cells on the collagen thin film were performed by a Hioki IM3570 impedance analyzer across a frequency band of 10 kHz to 1 MHz at 10 mV. Fig. 2 shows the impedance measurement setup.