Dual-Mode Biosensor for Alkaline Phosphatase Detection Based on DCIP and Eu 3+ -Calcein

In this study, a simple and sensitive dual-mode biosensor was designed based on the color of 2,6-dichloroindiphenol (DCIP) and the fluorescence of calcein. The target alkaline phosphatase (ALP) can catalyze the dephosphorylation of L-ascorbic acid-2-phosphate (AAP) to form ascorbic acid (AA) and phosphate ions. The reducing properties of AA can reduce the DCIP from blue to colorless. Meanwhile, phosphate ions can chelate with europium ions (Eu 3+ ) to restore the fluorescence of Eu 3+ -Calcein. In colorimetric mode, the linear detection range for ALP was 1.56-50 U/L with a limit of detection (LOD) of 0.27 U/L. In fluorescence mode, the linear detection range was 0.78-25 U/L and LOD was 0.23 U/L. Besides, the selectivity of this dual-mode for ALP was very excellent and the recovery rates in serum samples were also satisfactory.