Up-conversion fluorescence “off-on” switch based on heterogeneous core-satellite assembly for thrombin detection

NaGdF4: Yb, Er nanoparticles, with up-conversion (UC) fluorescence, were used for the first time to build an “off-on” switch based on Au core-UC satellites for thrombin detection. We fabricated the fluorescence sensor using thrombin aptamer modified Au core and complementary sequence modified UC satellites in liquid phase. With optimized assembled conditions, the yield of Au core-UC satellites achieved 80%. The fluorescence of UC nanoparticles quenched when satellite NP attached to Au core NP. Thrombin aptamer on the surface of Au core would bind to targets when thrombin existed in the system, then UC satellites were released and the quenched fluorescence recovered. The sensor showed high specificity for thrombin compared with other biomolecules and the limit of detection reached 3.5 fg/mL. Application of this sensor to detect targets in human serum also achieved satisfactory results. The purpose of this work was to build an ultrasensitive sensor based on Au core-UC satellites for thrombin detection in human serum to achieve diagnosis of diseases.