Europium-based core-shell materials for fluorescence and colorimetric dual-mode sensing of alkaline phosphatase activity

Abstract

Abnormal alkaline phosphatase levels have been associated with several diseases, including tumor growth, diabetes, liver dysfunction and so on. Generally, the occurrence and prognosis of these diseases can be reflected by the serum alkaline phosphatase level. In this work, Eu/DBM@SiO₂@SiO₂ is prepared to protect the internal Eu complex from the external environment by wrapping Eu/DBM inside the silica shell. Then, Eu/DBM@SiO₂@SiO₂/MnO₂, a sensor consists of Eu/DBM@SiO₂@SiO₂ and MnO₂, is prepared and applied for alkaline phosphatase detection. MnO₂ is used as the response part of alkaline phosphatase, which can be degraded to Mn²⁺ by ascorbic acid. Ascorbic acid is the hydrolysate of alkaline phosphatase. In the process of this reaction, UV–vis absorption of Eu/DBM@SiO₂@SiO₂/MnO₂ is reduced and fluorescence is turned on. Alkaline phosphatase concentration is linearly correlated with the logarithmic value of fluorescence enhancement in the range of 10.0–100.0 U/L with linear equation of Lg(F/F₀)=0.008C-0.030 (R²=0.99). For fluorescence method, the LOQ is 10.0 U/L and the LOD is 4.4 U/L. For colorimetric method, the concentration of alkaline phosphatase is linearly correlated with the decrease of absorption intensity in the range of 20.0–90.0 U/L with the linear equation of A/A₀=-0.012C+1.148 (R²=0.99). The LOQ is 20.0 U/L and the LOD is 7.2 U/L. The detection system has good selectivity and can detect alkaline phosphatase in human serum samples, the accuracy of the detection system is verified by the experiment of spike-in experiment. The RSD of alkaline phosphatase concentration in serum samples is in the range of 1.4–8.4 %. This method has potential application in the detection of ALP activity in biological samples.