DEVELOPMENT AND CHARACTERIZATION OF A MICROSENSOR DEVICE FOR REAL TIME OXYGEN MONITORING IN 3D TISSUE ENGINEERED CONSTRUCTS

The importance of oxygen concentrations in cell culture for tissue engineering and regenerative medicine is often underestimated1, although this parameter is crucial for cell fate during differentiation. The environmental oxygen concentration (20.9%) does not represent the physiological condition within human tissue2, such as bone and cartilage. For this reason, real time oxygen monitoring can improve the standardization of stem cell differentiation outcome, both for two‐dimensional (2D) and three‐dimensional (3D) methods. Therefore, we developed electrochemical oxygen sensors, already successfully applied in other fields3,4, using a copper wire inserted into a silica capillary tube, partly filled with a graphite‐loaded epoxy resin. The sensors were introduced into the tissue plates through modified tissue plate lids, and the detection of oxygen was obtained by means of an electrochemical reduction, i.e. applying a cathodic potential to the carbon‐disk surface. We tested the sensor stability in cell culture medium and its material cytotoxicity for bone marrow stem cells (BMSCs) cultures. The sensors are proved to be non‐cytotoxic for up to 7 days. and were not damaged over a period of 21 days in cell culture medium The sensors were subsequently used to analyze oxygen concentration in 3D cultures of BMSCs embedded in two different hydrogels, gelatin methacryloyl (GelMa) and tyramine functionalized hyaluronic acid (HAT). The embedded stem cells were differentiated in chondrogenic medium for 21 days, both under hypoxic and normal conditions. The proposed system has the potential to represent an easy way of in real time oxygen concentration measurements in 3D constructs during differentiation.