3.5. Cell proliferation of bioprinted LOC and drug response
The growth of hepatocytes on the LOC was determined using the CCK-8 proliferation assay kit over a period of 10 days. The graphical data of hepatocyte proliferation as percentage O.D. increase are shown in Fig. 7A. An increased hepatocyte proliferation rate was observed during the initial 7 days; the number of cells increased approximately tenfold. Post day 7, the proliferative capability reduced, and the growth of hepatocytes saturated. The considerable increase in the initial cell numbers was due to the abundant availability of medium and diffused gases throughout the in-vitro model as well as sufficient space for cellular growth and proliferation. This rapid increase in cell numbers during the first week reduced the per-cell-volume availability of medium components and diffused gases, inhibiting the cell growth cycle and resulting in increased cell necrosis. Furthermore, due to the overcrowding of cells, cell–cell contact inhibition occurred, which restricted cellular proliferation.