Fig 1.
Oxygen sensor-hypoxia chamber module.
(A) Close-up views of the Arduino Uno microcontroller board and half-sized breadboard mounted on acrylic plate. (B) Layout of the modular hypoxia chamber (with the oxygen sensor mounted on half-sized breadboard), the Arduino Uno microcontroller and the wire harness routed through one of the gas-flush tube ports, before assembly of the module (lid not shown). 30 AWG silicone-coated (orange colored) wires (cat. no. 2001, adafuit.com) were used in this photograph to clearly illustrate the wire harness.
Table 1.
Required electronic partsa and accessoriesb.
Fig 2.
Schematic of the logic converter and connections.
Pin designations of the 4-channel bi-directional logic converter (low-voltage pins A1, A2 and high voltage pins B1, B2 were used. A3, A4 and B3, B4 pins are extra, and not needed in this application). The logic converter is supplied as a mini printed circuit board (PCB) with a pair of 6-pin headers to facilitate mounting on a breadboard. We used a 30W soldering iron (RadioShack) fitted with a 15-watt soldering iron tip (cat. no. 64–2052, RadioShack) and 0.787 mm (0.032") flux-cored solder wire (cat. no. 64–005) to solder the PCB to the 6-pin headers. The soldered PCB was fitted on the half-sized breadboard mounted alongside the Arduino board.
Fig 3.
Outline of the wiring diagram.
A Fritzing (fritzing.org) sketch is presented outlining the wiring connections between the microcontroller, the logic converter, and the oxygen sensor.
Fig 4.
Screen-capture images of CoolTerm terminal window.
Upper panel: CoolTerm quick access bar and ribbon; middle panel: format of the initial data output from CoolTerm; lower panel: format of the final data saved by CoolTerm with time-stamps (saved and opened as a Microsoft Notepad file).
Fig 5.
Representative oxygen and temperature data transmitted by the sensor under experimental conditions.
(A) change in chamber O2% upon a single 4 min (20 L/min) anoxic gas purge conducted in the presence of cell cultures. (B) lack of a rapid initial increase in O2% when chamber is devoid of any cell cultures, liquid media or water. (C) change in chamber O2% with a post-1 day gas purge (in the presence of cell cultures). (D) change in chamber O2% with daily gas purges in the presence of cell cultures. (E) pressure profile of experiment listed in D. (F) change in chamber O2% profile upon inclusion of ten cell culture plates.
Fig 6.
Oxygen and temperature changes during programmed adjustment of hypoxia.
A single 24-well plate of cell cultures was used and monitored over 48 hrs. (A) The sealed modular hypoxia chamber was placed in cell culture incubator (without a purge with anoxic gas-mix). The chamber was then flushed with the anoxic gas-mix at an initial flow rate of 20 L/min (approx. 2 min) to lower the O2 level from 21% to 5%. This was followed by a slower flow rate of 5 L/min (approx. 3 min) until O2% reached 0.5%. (B) expanded view of the change in O2% during the initial 5 min programmed purge procedure.