![]() The data (O 2, temperature, pressure) are recorded and time-stamped using a free terminal program (CoolTerm, ), that can store up to 2 MB of serial data. Data are forwarded to a computer for the duration of the experiment via the microcontroller's USB port. The Arduino microcontroller is programmed with a simple instruction set (Arduino sketch) developed by the authors that acquires data from the O 2 sensor at preset time intervals based on user input (for example, at 1 sec or 5 min intervals). The wires are routed through one of the gas-ports of the chamber, and thus do not require compromising the physical integrity of the chamber. ![]() The sensor is placed in the modular hypoxia chamber and connected to an externally located Arduino kit via hair-thin insulated copper wires (0.127 mm diameter, Temco Industrial Power, CA, USA), commonly used for winding electromagnets. Chamber O 2 is monitored using a factory calibrated miniature gas sensor (Luminox-02, SST Sensing Ltd., Coatbridge, UK) that can simultaneously measure temperature and pressure also. In this report, we describe the development of a low-cost sensor module based on a popular microcontroller kit (Arduino Uno,, Italy) for continuous measurement of O 2 concentration in hypoxia chambers. Thus, researchers in non-computer related fields could develop and embed these sensor-incorporated kits in basic scientific apparatus to monitor and record experimental parameters that were not previously possible. The microcontroller programming steps are intuitive with user-friendly with instructions that do not require advanced programming skills. gas, temperature, pressure, humidity, or light detectors), and program the microcontroller to acquire data. With the availability of numerous low-cost open-source (software and hardware that can be freely used, modified, and shared by anyone) microcontroller kits for educational and hobby electronics, a researcher can now interface these with environmental sensors (e.g. However, since these modular units lack any sensor or detection system to monitor gas-phase O 2, it is not possible to identify any changes to the O 2 concentration in the chamber for the duration of the hypoxia experiment the O 2 level in the chamber is assumed to remain constant for the duration of the 48–72 hr experiment. Manufacturers recommend a second purge with the gas pre-mix 1 hr later to remove any residual trapped air. The chamber is sealed and placed in a laboratory incubator (37☌) to culture the cells under hypoxic conditions. 4 min at 20 L/min), usually with a pre-formulated gas mixture of 1% O 2, 5% CO 2, and 94% N 2. Tumor cell cultures are placed in the chamber and the chamber purged via a pair of ports for a predetermined time-period (e.g. These semi-spherical polycarbonate chambers of approximately 8 liters in volume cost approximately $700 for a modular chamber and a gas-flow meter. Billups-Rothenburg, Inc., CA, USA StemCell Technologies, Inc., Vancouver, BC, Canada) to recapitulate the tumor hypoxic conditions during in vitro cell-culture studies. Research laboratories routinely use portable modular incubator chambers (e.g. Although it was previously thought that hypoxic regions are primarily located in the tumor “core”, recent investigations indicate that such hypoxic regions are more heterogeneously distributed within the bulk tumor. ![]() The studies suggest that an O 2 concentration of 1.3% or below marks the threshold for altered metabolic changes in tumors metabolism remains relatively unaltered at higher O 2 concentrations. These hypoxic regions help support the tumor against chemotherapy, radiation therapy, and alter the tumor's metabolism in such a way to help it invade and metastasize throughout the patient's body. Rapidly growing tumors, particularly those that are malignant, contain regions of low O 2 within the tumor mass.
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