Fig. 6: Changes of the impedance phase of MSCs and HUVECs cultured on
collagen thin films with concentrations of 250 \(\mu g/mL\), 500\(\mu g/mL\), 1000 \(\mu g/mL\) over time.
Effect of the collagen thin films on the MDA-MB-231 cells
In the second step of the research, tests were accomplished on the
MDA-MB-231 to explore the effect of the collagen thin film concentration
on the growth and proliferation of the cancer cells. This experiment was
performed twice for four concentrations and five samples from each
concentration. These cells did not attach to the collagen thin films in
any of the samples and died. In general, cancer cells produce
collagenase. Collagenase is an enzyme that dissolves and destroys
collagen. In particular, MDA-MB-231 cells, which are aggressive and
malignant, show this behavior more strongly. Three mammalian
collagenases (MMP-1, MMP-8, MMP-13) [42] appertain
to the group of matrix metalloproteinases and can cleave and destroy the
extracellular collagen matrix [42]. In addition to
the fibrillar collagens, collagenases can cleave and destroy some other
extracellular matrices and non-matrix proteins, including growth factors[42]. MMPs are commonly thought of as tumor growth
enzymes because they destroy extracellular matrix components and thus
increase the invasive power of the cancerous cells[43]. It seems that due to the fact that these
collagenases have been observed in breast cancerous cells[44], they can destroy the thin layers of the
collagen. By destroying these thin layers, which are considered as a bed
for the cell attachment, the cells do not found an appropriate substrate
to attach and die.
Bioimpedance assessment of the collagen thin films
concentration on the HUVECs proliferation rate
In the third step of the research, collagen thin films were created on
the surface of the alkanethiol-treated IDEs and the role of the
concentration of the collagen thin films on the growth and proliferation
of the HUVECs was quantitatively investigated using impedance
measurements. Like the MSCs, viability assessment of HUVECs showed no
remarkable discrepancy among the viability of HUVECs cultured on the
collagen thin films with different concentrations. The HUVECs cultured
on the collagen thin films with various concentrations had a viability
of over 99%. As well, obtained impedance results were analogous with
the results of the MSCs.
3.4.1 Bioimpedance magnitude of the HUVECs cultured on
the collagen thin films
The impedance measurement results of the HUVECs were similar to that of
the MSCs. Fig. 4 (D-F) shows the magnitude diagram of the measured
impedances of the HUVECs cultured on the collagen thin films with
different concentrations during the time. As shown in the figure, the
magnitude of the measured bioimpedance at different concentrations of
collagen thin films has increased over time. This increase in the
impedance in the first hours results from the cell attachment. After 48
h, the increased impedance magnitude is due to the cell proliferation
since the cell numbers have been increased because cells doubling time
has elapsed. The diagram of the measured differential bioimpedance for
different concentrations after 48 h is also shown in Fig. 5 (B). We can
see in this figure that after 48 h, when the doubling time (about 36 h)
of the HUVECs has elapsed, the amount of increase in impedance at lower
concentrations is higher than that of the higher concentrations, which
may indicate more cell growth on the collagen thin films with lower
concentration.