Simplified optical monitoring systems for detecting leukocyte-derived hypochlorite ions using small amounts of whole blood

Here, we developed two simplified optical systems, FLP-H3200 and FLP-H4200, designed to detect leukocyte-derived hypochlorite ions via fluorescence (FL-OCl − ) using only three microliters of whole blood. First, the new systems employed a lower-cost photodiode as the photodetector instead of a photomultiplier tube in their preceding system CFL-H2200. The systems featured a simplified optical configuration optimized for the blood measurement fluidic chip, enabling efficient focusing of the desired FL-OCl − signal and obtaining a signal intensity comparable to that obtained with CFL-H2200. These improvements made the new systems more compact, lightweight, and cost-effective than CFL-H2200. Additionally, in FLP-H4200, the intensity of the excitation light source, the light-emitting diode, was set higher than that in FLP-H3200, further enhancing the FL-OCl − signal. Using the fluorescent reagent fluorescein, we confirmed that the fluorescence sensitivity of the new systems was comparable to that of CFL-H2200. Finally, blood analysis data using FLP-H3200 and FLP-H4200 showed a high correlation. This study broadens the scope of clinical examinations by providing accessible and efficient tools for monitoring leukocyte activity using whole blood. • FLP-H3200 and FLP-H4200 were developed to monitor OCl − ions produced by leukocytes. • These systems are more compact, lightweight, and cost-effective than previous ones. • The fluidic chip used enables detection using three microliters of whole blood. • FLP-H4200 delivers increased fluorescence signals with a higher LED intensity. • Signals from FLP-H3200 and FLP-H4200 show a strong positive correlation.