Fabrication of micro-cages and caged tumor spheroids for microfluidic chip-based assays

We developed a simple method to fabricate micro-cages and caged tumor spheroids for microfluidic chip-based assays. The micro-cage device consists of an array of honeycomb compartments with a monolayer of cross-linked and agarose-coated gelatin nanofibers at the bottom and a mesh of 200 pm hole-size on the top. U87-MG single cells were dispersed through the mesh and resulted tumor spheroids confined in each of the cage compartment after incubation. As expected, the tumor spheroids are one-by-one distributed in each of the compartment with the same size and they grew inside the compartments. The final size of the spheroid was limited by both diffusion and confinement. If the height of the cage is small, the nanofiber layer underneath tumors could be deflected due to mechanic stress of growing tumors. If the height of the cage is large, tumors grew freely without stress but their size was limited by diffusion. In both cases, tumors tended to remain in spherical shape. To illustrate the robustness of the approach, the tumor caged device was reversibly integrated into a microfluidic chip for drug test. Our results show that under tangent flow conditions, combretastatin A-4 had a clear effect on tumor disassembling.