FIG. 3.

Schematic of model system. (A) Schematic of bioreactor culture system indicating bioreactors (green arrow) and ports with Luer fittings for tubing for perfusion (red arrows) and gas exchange (blue arrow). (B) Syringe pump and assembled bioreactor setup for perfusion. (C) Close-up view of bioreactors within culture system. (D) Three-dimensional view of bioreactor and oxygen probe measurement system. The polydimethylsiloxane bioreactor system (1) is housed within an oxygen probe housing setup, which uses a micromanipulator (2) to allow precise positioning of the oxygen probe (3). Custom-made Delrin pieces serve as a bioreactor holder (4), probe mount (5), and probe holder (6), respectively. (E) Bottom view of system schematic showing oxygen probe within well of bioreactor. Blow-up of well (2 × 1.5 cm) demonstrates the silk tube within the collagen gel, which is under either static or perfusion conditions, with the oxygen probe entering from the side and measuring the oxygen gradient as a function of distance from the tube. Color images available online at www.liebertonline.com/ten.