Direct and rapid measurement of hydrogen peroxide in human blood using a microfluidic device

The levels of hydrogen peroxide ( H 2 O 2 ) in human blood is of great relevance as it has emerged as an important signalling molecule in a variety of disease states. Fast and reliable measurement of H 2 O 2 levels in the blood, however, continues to remain a challenge. Herein we report an automated method employing a microfluidic device for direct and rapid measurement of H 2 O 2 in human blood based on laser-induced fluorescence measurement. Our study delineates the critical factors that affect measurement accuracy—we found blood cells and soluble proteins significantly alter the native H 2 O 2 levels in the time interval between sample withdrawal and detection. We show that separation of blood cells and subsequent dilution of the plasma with a buffer at a ratio of 1:6 inhibits the above effect, leading to reliable measurements. We demonstrate rapid measurement of H 2 O 2 in plasma in the concentration range of 0–49 µM, offering a limit of detection of 0.05 µM, a sensitivity of 0.60 µM −1 , and detection time of 15 min; the device is amenable to the real-time measurement of H 2 O 2 in the patient’s blood. Using the linear correlation obtained with known quantities of H 2 O 2 , the endogenous H 2 O 2 concentration in the blood of healthy individuals is found to be in the range of 0.8–6 µM. The availability of this device at the point of care will have relevance in understanding the role of H 2 O 2 in health and disease.