## 3 Results
### Cell Localization and Cellular Metabolism  
The cell localization and immobilization of Hep G2 and HUVECs cultured on the scaffold was observed by confocal microscopy after 10 days of the culture system, as shown in Figure 4a,b. The z-stack-compiled volume view demonstrates the coverage of both the Hep G2 and HUVECs layer on the scaffold, as shown in Figure 4b. The full coverage of endothelial cells or endothelial is important to study blood compatibility. However, the limitation of macroporous structure of the scaffold was the visualization of the full coverage of the endothelial cells throughout the scaffold for live imaging. Hep G2 and HUVECs attachment on the scaffold could also be observed under SEM, as demonstrated in the Figure 4c. Endothelial cells plays a major role in the regulation of coagulation [28], mainly mediating the interaction between blood and tissues. Therefore, the coverage of endothelial cell lining can mitigate the formation of thrombus when the scaffold comes in contact with blood, thereby improving the antithrombotic capacity of the biomaterial.  
Figure 2: (**a**) Computer aided design (CAD) model and dimension of the 3-D scaffold; (**b**) fabricated three-dimensional scaffolds after selective laser sintering (SLS) printing and micro-CT scan. The scale bars are 10 mm. (i) Slices from different layers of the scaffold with internal diameters of the channel of 2 mm (ii), 1.5 mm (iii), and 1 mm (iv); (**c**) cross section of the internal diameter of interconnected channel (scale bar 10 mm, magnification 5\(\times\). The slices of cross section I (approximately channel diameter 2 mm), cross section II (approximately channel diameter 1.5 mm), and cross section III (approximately channel diameter 1 mm) was sliced from region I, II, and III as depicted in (**b**).  
The glucose uptake and lactate production by Hep G2 and the co-culture were compared and are shown in Figure 5a. We observed that at day 10, the consumption of glucose  
Figure 4: (**a**) Live imaging of Hep G2 and human umbilical vein endothelial cells (HUVEC) after 10 days of perfusion culture (scale bars 100 \(\upmu\)m, magnification 4\(\times\)); (**b**) volume z-stacked view of the Hep G2 and HUVEC cultured on the scaffold; (**c**) SEM images of Hep G2-covered scaffold and co-culture of Hep G2 and HUVEC at day 10. The yellow arrows show the morphology of Hep G2 and HUVEC grown on the scaffold (scale bar 100 \(\upmu\)m, magnification 200\(\times\)).  
Figure 3: (**a**) Morphology of the PCL and PGA microparticle under scanning electron microscopy (SEM) (scale bar 100 \(\upmu\)m, magnification 500\(\times\)); (**b**) the % of porosity of the 3-D construct versus energy density. Each column represents mean \(\pm\) SD with \(n\) = 3 independent experiments; (**c**) morphology of the macroporous scaffold after leaching out of PGA microparticle under SEM, showing the porous network (scale bar 500 \(\upmu\)m, magnification 100\(\times\) and 200 \(\upmu\)m, magnification 200\(\times\)).  
of the co-culture system was significantly higher than the pure Hep G2 culture condition. On the other hand, the lactate production of the co-culture system was significantly lower than the pure Hep G2 culture condition. The metabolism of glucose uptake and lactate production indicate the overall environment of the culture system. Accumulation of high lactate can create an acidic environment and may lead to the induction of oxidative stress, thereby affecting the health of the cells. Therefore, it is vital to maintain the nonacidic environment for healthy cell growth.  
The albumin production was monitored every 2 days until day 10. The highest albumin production was observed at day 10 for the Hep G2-cultured scaffold, whereas there was significant reduction in the case of the co-culture condition from Figure 5b. The lower production of albumin may be due Hep G2, as well as HUVECs, striving for glucose. Therefore, further optimization is needed to resolve the effect of endothelial lining on Hep G2 in the macro scaffold under the perfusion culture system.