N -(4-Aminobutyl)- N -ethylisopropanol and Co 2+ Dual-Functionalized Core-Shell Fe 3 O 4 @Au/Ag Magnetic Nanomaterials with Strong and Stable Chemiluminescence for a Label-Free Exosome Immunosensor.

Recently, magnetic beads (MBs) are moving toward chemiluminescence (CL) functional magnetic nanomaterials with a great potential for constructing label-free immunosensors. However, most of the CL-functionalized MBs suffer from scarce binding sites, easy aggregation, and leakage of CL reagents, which will ultimately affect the analytical performance of immunosensors. Herein, by using core-shell Fe 3 O 4 @Au/Ag magnetic nanomaterials as a nanoplatform, a novel N -(4-aminobutyl)- N -ethylisopropanol (ABEI) and Co 2+ dual-functionalized magnetic nanomaterial, namely, Fe 3 O 4 @Au/Ag/ABEI/Co 2+ , with strong and stable CL emission was successfully synthesized. Its CL intensity was 36 and 3.5 times higher than that of MB@ABEI-Au/Co 2+ and ABEI and Co 2+ dual-functionalized chemiluminescent MBs previously reported by our group, respectively. It was found that the excellent CL performance of Fe 3 O 4 @Au/Ag/ABEI/Co 2+ could be attributed to the enrichment effect of the Au/Ag shell and the synergistic enhance effect of the Au/Ag shell and Co 2+ . A related CL mechanism has been proposed. Afterward, based on the intense and stable CL emission of Fe 3 O 4 @Au/Ag/ABEI/Co 2+ , a sensitive and effective label-free CL immunosensor for exosome detection was established. It exhibited excellent analytical performance with a wide detection range of 3.1 × 10 3 to 3.1 × 10 8 particles/mL and a low detection limit of 2.1 × 10 3 particles/mL, which were better than the vast majority of the reported CL immunosensors. Moreover, the proposed label-free CL immunosensor was successfully used to detect exosomes in human serum samples and enabled us to distinguish healthy persons and lung cancer patients. It has the potential to be a powerful tool for exosome study and early cancer diagnosis.