Novel sliding hybrid microchip detection system for determination of whole blood phosphorus concentration

A novel detection system consisting of a three-dimensional (3-D) sliding hybrid microchip (SHM) and a smart analysis device is presented to determine the phosphorus concentration in whole blood samples. The novelty of the SHM detection system includes filtering whole blood directly into serum, reacting different reagents in stages, performing a closed-type reaction to prevent evaporation of the test sample and uniform heating. The SHM is fabricated on PET and PMMA substrates and incorporates a sample injection zone, a filter paper-strip, two paper-chip reagent zones (reagent A and reagent B), and a detection zone. In the proposed detection method, 6 μL of whole blood sample is injected into the sample chamber and is filtered / separated by the paper-strip as it diffuses toward reagent zone A under the effects of capillary action. After 1 min, the sliding mechanism of the SHM is activated such that reagent zone B is positioned over reagent zone A in the detection/reaction zone. The SHM is then inserted into the smart analysis device and heated at 35°C for 4 min to prompt a modified molybdenum blue reaction. Finally, the blood phosphorus concentration is measured through a colorimetric method performed by a self-developed color analysis app installed on a smartphone. The feasibility of the current SHM detection system is demonstrated by the known control serum phosphorus concentrations ranging from 0.1–9 mg/dL. It is shown that the total R + B + G color intensity of the reaction complex image (Y) is linearly related to the serum phosphorus concentration (X) as Y = -31.502X + 600.740. The coefficient of determination (R²) and detection limit are 0.9936 and 0.06 mg/dL, respectively. The phosphorus concentration detection results obtained using the current SHM system for the whole blood samples of 100 real-world chronic kidney disease (CKD) patients are shown to be in excellent consistent with the detection results acquired through a macroscopic technique. Overall, the current SHM detection system provides a rapid and reliable method to detect the phosphorus concentration in whole blood samples.