A novel sandwich-type fluorescent sensor for the selective and sensitive detection of ellagic acid based on boronate affinity oriented imprinting and silver nanoparticle-enhanced fluorescence of boronic acid-modified CdTe quantum dots.

Ellagic acid (EA) exhibits remarkable in-vivo bioactivity and antioxidant properties. EA is also a skin-whitening agent. Accurate quantification of EA is crucial for the effective use of EA-rich foods and cosmetics. In this study, we develop a novel sandwich-type fluorescent sensor for the specific and sensitive detection of ellagic acid based on boronate affinity oriented imprinting and silver nanoparticle-enhanced fluorescence of boronic acid-modified quantum dots (QDs). Oriented imprinting achieves high specificity and affinity, while Ag@SiO decorated with boronic acid-immobilized QDs offers high sensitivity. Maximum metal-enhanced fluorescence intensity occurs with a silica shell thickness of approximately 10 nm. This approach demonstrates a wide linear range (0.1-10 ng/mL) and a low LOD (0.0438 ng/mL). The recoveries ranged from 91.1 % to 108.2 % and 91.3 % to 107.8 % in strawberries and cosmetics, respectively. As compared with previously reported methods for EA detection, the sandwich-type fluorescent sensor provided two orders of magnitude higher sensitivity at least.