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

The levels of hydrogen peroxide ([Formula: see text]) 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 [Formula: see text] 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 [Formula: see text] 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 [Formula: see text] 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 [Formula: see text] 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 [Formula: see text] in the patient's blood. Using the linear correlation obtained with known quantities of [Formula: see text], the endogenous [Formula: see text] 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 [Formula: see text] in health and disease.