A sensitive electrochemiluminescence immunosensor for carbohydrate antigen 12-5 analysis based on dual-function SnO2 nanoflowers

Tin oxide nanoflowers (SnO2NFs) are used as both an electrochemiluminescent (ECL) signal generator and a carrier of nanomaterials due to the advantages of excellent electrical conductivity, large specific surface area, and good optical properties. AuNPs/PEI-SnO2NFs provide a larger binding site for the immobilization of secondary antibodies (CA12-5-Ab2). The synthesized Ag@ZnONS composite with a large specific surface area and good biocompatibility was applied to immobilize more primary antibodies (CA12-5-Ab1), which further enhanced the ECL signal and obviously improved the sensitivity and selectivity of the immunosensor. A novel signal amplification ECL immunosensor for detecting carbohydrate antigen 12-5 (CA12-5) was fabricated with AuNPs/PEI-SnO2NFs as a signal probe and Ag@ZnONSs as the sensing matrix. The ECL intensity was linearly related to the logarithm of the CA12-5 concentration in the range from 1 × 10−5 to 50 ng mL−1 under optimized conditions. The limit of detection was 2.6 fg mL−1 (S/N = 3). The assay had good operational stability, specificity, and high sensitivity. The study was applied to analyze the CA12-5 level in human serum with satisfactory results, which could be applied in clinical immunoassays.