3D micro fabrication and screening

A method, comprising

• (a) providing a three-dimensional (3D) cell growth medium comprising a plurality of hydrogel particles and a liquid cell culture medium, wherein the hydrogel particles are swelled with the liquid cell culture medium to form a granular gel, wherein the 3D cell growth medium has a yield stress such that the cell growth medium undergoes a phase change from a solid phase to a liquid phase upon application of a shear stress greater than the yield stress, wherein the yield stress is 1 to 100 Pa;
• (b) depositing one or more cells into the granular gel with a depositing device by applying a first shear stress greater than the yield stress of the 3D cell growth medium to change the 3D cell growth medium into a liquid phase, wherein after the cells are deposited and the shear stress is removed, the 3D cell growth medium fills in space created by the depositing device before changing to a solid phase and trapping the cells at the desired location;
• (c) culturing the cells for a first period of time;
• (d) collecting a first sample from the granular gel with a collection device by applying a second shear stress greater than the yield stress of the 3D cell growth medium to change the 3D cell growth medium into a liquid phase, wherein after the first sample is collected and the shear stress is removed, the 3D cell growth medium fills in space created by the collection device before changing to a solid phase;
• (e) culturing the cells for a second period of time;
• (f) repeating step (d) to collect a second sample;
• and
• (g) analyzing the first sample, the second sample, or a combination thereof, to evaluate changes in the cells or the extracellular environment.