4.6.2 The effect of printed pressure on cell adhesion and
proliferation
In vitro culture of HUVECs in samples: KC-SA-C-15kPa,
KC-SA-C-25kPa, and KC-SA-C-35kPa,to assess the effect of printing
pressure on the morphology of endothelial cells, the nucleus (blue) and
cytoskeleton (green) were stained after endothelial cells laden
hydrogels were printed after 24, 48, and 72 h (Figure 13(a–i)).
The proliferation and adhesion of cells increased with an increase in
the printing pressure. The cell adhesion in the KC-SA-C-35kPa scaffold
was not only more than that in KC-SA-C-15kPa and KC-SA-C-25kPa but also
the cell adhesion density and proliferation migration on KC-SA-C-35kPa
at the same culture time was significantly better than those under other
printing pressures.
Moreover, the diffusion area of cells in the scaffold of other pressures
was lower than that in the KC-SA-C-35kPa scaffold. The cells were
distributed more uniformly and showed better interaction and fusion with
each other in the KC-SA-C-35kPa scaffold. After 24 h of cell culture,
the pseudopod spread area of cells in the KC-SA-C-35kPa scaffold was
larger, and the interaction among cells was more obvious after 48 h of
culture, indicating a tendency of endothelialisation until 72 h of
culture.
Cell adhesion, proliferation, and distribution can be attributed to the
microstructures and properties of the scaffold.As shown in the
microstructure and of KC-SA-C-0.3(Figure 10), most pores were either
incompletely formed or had excessively large pore size in the
KC-SA-C-15KPA scaffold, which was not conducive to the initial cell
adhesion and subsequent growth parameters. Moreover, the cells grew well
in the KC-SA-C-35kPa scaffold, possibly because the KC-SA-C-35kPa
scaffold had a porous structure with an outer diameter of 3–50 m and a
regular and elliptical distribution; this pore size is conducive to cell
growth. The orientation growth of cells was observed in the
KC-SA-C-35kPa scaffold, possibly caused by the radial orientation of
pores in the printed structure, that is, the shear force was distributed
along the radial gradient of the printed structure.
In general, the adhesion cells formed effective adhesion 6 h after
growth on the material. Therefore, under similar culture conditions, the
cell density in the material after 24-h seeding reflected the cell
adhesion ability. The cell density of fluorescent images was
statistically analysed using the Image-Pro Plus 6.0 software to evaluate
the adhesion ability of HUVECs (Figure 14). As shown in Figure 14, the
absorbance of cells in the KC-SA-C-35kPa scaffold was the highest,
followed by that in the KC-SA-C-25kPa and then in KC-SA-C-15kPa
(lowest). Moreover, the initial adhesion of cells in the KC-SA-C-35kPa
scaffold was much higher than that in other scaffolds. After 48 h of
culture, the number of cells in the KC-SA-C-35kPa scaffold was the
highest, almost covering the entire region, while that in the
KC-SA-C-15kPa scaffold was the least, with the trend becoming more
obvious after 72 h of culture.
The results together demonstrated that a larger printing pressure is
conducive to the uniform distribution of cells, with rapid proliferation
and promotion of endothelialisation. Low printing pressure leads to
uneven cell distribution, local sedimentation, and aggregation, which
are not conducive to cell growth and proliferation.