Catheter-tip sensor to monitor production of hydrogen peroxide in small biosamples

Recently, it was shown that antibodies in the presence of ultraviolet (UV) light give rise to singlet oxygen which ultimately leads to the production of hydrogen peroxide (H2O2). In this research, we are interested in understanding the role of H2O2 in T-cell activity during inflammation. Since the T-cell receptor has been shown to have the same oxidative catalytic potential as antibodies, we started experiments measuring H2O2 production in antibodies and T cells. After showing that a positively polarized Clark oxygen electrode can be used in measuring H2O2 production in antibodies and T-cells, it is the goal of the current study to characterize the use of a catheter-tip sensor under similar conditions. Our catheter has a platinum ring which acts as the anode and a silver/silver chloride tip which acts as the cathode. Although this newly designed amperometric biosensor works on the same principles of electrochemistry, its compact size equips us with the potential for in vivo use and small sample testing. Operating at a polarizing voltage of 0.7 Volts v/s Ag/AgCl, the bare sensor produced a current of 8 +/- 2 nA per microM H2O2 with a 10 seconds response time, over a range of 0-50 microM H2O2. For use with biosamples, we added a hydrophilic H2O2 permeable membrane, which reduced the electrode current to 0.48 +/- 0.1 nA/microM H2O2 and increased the response time to 2 minutes. On the other hand, the addition of the membrane improved the signal to noise ratio and the selectivity of the sensor. Using this sensor, we reproduced the light mediated H2O2 production which was recorded at the rate of 20 nM per minute for 1 milliliter of 6.7 microM rat IgG solution. We further discuss the usefulness, limitation and the future scope of this real time monitoring system for H2O2 research using small biosamples.