A fluorescent aptasensor for highly sensitive and selective detection of carcinoembryonic antigen based on upconversion nanoparticles and WS2 nanosheets

Abstract

A highly sensitive fluorescent aptasensor for carcinoembryonic antigen (CEA) was developed by employing upconversion nanoparticles (UCNPs) as an energy donor and WS₂ nanosheets as an energy acceptor, respectively. Polyacrylic acid (PAA) modified NaYF4:Yb/Er UCNPs and an amine modified CEA aptamer were linked together by a covalent bond. Owing to the physical adsorption between WS₂ nanosheets and the CEA aptamer, the UCNPs–aptamer was close to WS₂ nanosheets, resulting in upconversion fluorescence energy transfer from UCNPs to WS₂ nanosheets, and the UCNP fluorescence was quenched. With the introduction of CEA into the UCNPs–aptamer complex system, the aptamer preferentially bound to CEA resulting in a change in spatial conformation which caused UCNPs to depart from WS₂ nanosheets. As a result, the energy transfer was inhibited and the fluorescence of UCNPs was observed again, and the degree of fluorescence recovery was linearly related to the concentration of CEA in a range of 0.05–10 ng mL⁻¹ with a limit of detection of 0.008 ng mL⁻¹. Furthermore, the aptasensor based on UCNPs and WS₂ nanosheets could be competent for detecting CEA in human serum, which suggests the great application potential of the proposed aptasensor in clinical diagnosis.