From 2007.igem.org

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Organ and tissue synthesis often requires specific arrangement of underlying cells to act as a substrate for adhesion and development. Modern rapid prototyping uses UV polymerizing chemicals or layered printing to produce 3D replicas of parts. Here we propose a system to produce a predictably structured 3D cell mass.

The system requires six biological components:

1. Red Photosensor.
2. Blue Photosensor.
3. And Gate.
4. GFP Fluorescent reporter.
5. Promotable surface expression of cadherins.
6. Gas vesicle expression to produce neutrally buoyant bacteria.

The final system design is:

• Induce or Constitutively express gas vesicles for neutal buoyancy.
• If (Induced & Red & Blue) then Promote integrins, otherwise do not.

The system is used by preparing a beaker of neutrally buoyant bacteria in LB. The beaker is exposed to a pattern (eg a rectangular beam) of red light from one side, and a pattern of blue light from the top (eg a round beam). The Ecoli in the intersecting volume express cadherins and begin to aggregate as Brownian motion causes them to bump into each other, As the object (eg a cylinder) forms the area around the object becomes depleted of Ecoli. Diffusion from the surrounds will replace the Ecoli. The Brownian motion of the forming object will become less significant as it’s size increases. The object should stay positioned because, being the sum of neutrally buoyant parts, it will be neutrally buoyant.

By using an anular beam instead of a round one a tube could be formed, like a blood vessel.