A fluorescent aptasensor for highly sensitive and selective detection of carcinoembryonic antigen based on upconversion nanoparticles and WS 2 nanosheets.

A highly sensitive fluorescent aptasensor for carcinoembryonic antigen (CEA) was developed by employing upconversion nanoparticles (UCNPs) as an energy donor and WS 2 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 WS 2 nanosheets and the CEA aptamer, the UCNPs-aptamer was close to WS 2 nanosheets, resulting in upconversion fluorescence energy transfer from UCNPs to WS 2 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 WS 2 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 WS 2 nanosheets could be competent for detecting CEA in human serum, which suggests the great application potential of the proposed aptasensor in clinical diagnosis.