Design and fabrication of micro/bio chip for in vitro fabrication of toroidal cellular aggregates

The unique geometry of toroidal cellular aggregate has caught much attention during last few years due to its variety of applications in tissue engineering. For example, the micro lumen of connected toroidal aggregates enables a communication channel for vascularization within complex cellular constructs. This channel significantly helps preventing the cell death, due to the lack of nutrients. Furthermore, the direct assembly of multiple toroidal aggregates results in the formation of tissue engineered blood vessel, which is highly needed for transplantation in clinical use. In this paper, we design and fabricate a micro/bio chip enabling the fabrication of toroidal cellular aggregates. The chip has a 3×3 array of deformable scaffolds. Each scaffold has a diameter of 500 μm, a depth of 250 μm, a 130 μm-diameter pillar located in the middle, and a 20 μm-thick membrane coated on the top surface. The temporary toroidal scaffold is generated by decompression before cell seeding, and maintained until the cellular structure is strong. The 1.5×10⁵ cells of NIH3T3 were seeded in a chip, and cellular formation of toroidal shape was observed after 3 days. The retrieved aggregates have an outer diameter of about 330 μm, a lumen diameter of about 40 μm, and a thickness of about 100 μm. The cell viability test confirms the healthy condition of the aggregates. Moreover, the noninvasive recovery of the toroidal aggregates provided by the elastic membrane of the scaffolds suggests effectiveness of using this chip in biological applications.