Ultrasensitive Point‐of‐Care Test for Tumor Marker in Human Saliva Based on Luminescence‐Amplification Strategy of Lanthanide Nanoprobes

The point‐of‐care detection of tumor markers in saliva with high sensitivity and specificity remains a daunting challenge in biomedical research and clinical applications. Herein, a facile and ultrasensitive detection of tumor marker in saliva based on luminescence‐amplification strategy of lanthanide nanoprobes is proposed. Eu(2)O(3) nanocrystals are employed as bioprobes, which can be easily dissolved in acidic enhancer solution and transform into a large number of highly luminescent Eu(3+) micelles. Meanwhile, disposable syringe filter equipped with nitrocellulose membrane is used as bioassay platform, which facilitates the accomplishment of detection process within 10 min. The rational integration of dissolution enhanced luminescent bioassay strategy and miniaturized detection device enables the unique lab‐in‐syringe assay of tumor marker like carcinoembryonic antigen (CEA, an important tumor marker in clinic diagnosis and prognosis of cancer) with a detection limit down to 1.47 pg mL(−1) (7.35 × 10(−15) m). Upon illumination with a portable UV flashlight, the photoluminescence intensity change above 0.1 ng mL(−1) (0.5 × 10(−12) m) of CEA can be visually detected by naked eyes, which allows one to qualitatively evaluate the CEA level. Moreover, we confirm the reliability of using the amplified luminescence of Eu(2)O(3) nanoprobes for direct quantitation of CEA in patient saliva samples, thus validates the practicality of the proposed strategy for both clinical diagnosis and home self‐monitoring of tumor marker in human saliva.