Assembly of multilayered hepatic lobule-like vascular network by using heptapole magnetic tweezer

In this paper, we have fabricated a multilayered hepatic lobule-like vascular network in a 3D tissue using a heptapole magnetic tweezer. The tissue consists of cell-laden hydrogels with 3D channel networks. To fabricate multilayered channel system, magnetic hydrogel fibers were manipulated by a magnetic tweezer. The hepatic lobule tissue shows a hexagonal structure with different sizes of veins. Six portal veins transfer the blood including nutrients and oxygen to a central vein by sinusoids. The portal and central veins are made by steel rods, whereas the magnetic hydrogel fibers has a role of sinusoids. An important point of this research is to connect two veins - portal and central vein - by magnetic fibers. For this, we used magnetic tweezer with seven poles to magnetize the steel rods. In order to generate high magnetic fields, we design magnetic tweezer with a flat tip and additional lower tweezer based on simulation data. The manipulation was performed in fibrin gel inside rat liver cells. By applying high magnetic fields, we attracted magnetic fibers to the steel rods and constructed 3D channel network in cellular structure. To verify the efficiency of the channel, we supply culture medium to the channel and then analyze the cell viability according to the distance from the channel. As a result, the cells located at close to the channel show higher cell viability than others.