MnCO₃ as a New Electrochemiluminescence Emitter for Ultrasensitive Bioanalysis of β-Amyloid_1–42 Oligomers Based on Site-Directed Immobilization of Antibody

Abstract

In this work, an electrochemiluminescence (ECL) immunosensor utilizing MnCO₃ nanospheres as a novel ECL luminophor and the HWRGWVC (HC-7) heptapeptide as an efficient antibody capturer for site-directed immobilization with high affinity was proposed. MnCO₃ nanospheres prepared by a homogeneous precipitation method exhibited high ECL efficiency, low toxicity, favorable biocompatibility, and excellent stability. After the functionalization of polydimethyldiallylammonium chloride (PDDA), the obtained MnCO₃/PDDA could combine with gold nanoparticles (Au NPs) via electrostatic interaction (MnCO₃/PDDA/Au). Besides, HC-7 as a small peptide ligand has demonstrated an ability to bind the Fc portion of an antibody with high affinity. Because the end of HC-7 is a cysteine, it can connect to MnCO₃/PDDA/Au via a Au-S bond. Then, the antibody could be effectively captured by HC-7 through specific interaction with a better maintained activity than traditional coupling reaction. To verify the practicability of the constructed immunosensor, β-amyloid_1-42 oligomers (Aβ) were employed as an analyte. On the basis of the above points, the immunosensor performed favorable ECL property to Aβ concentrations in a wide linear range (0.1 pg/mL to 10 ng/mL) with a low detection limit (19.95 fg/mL). With excellent repeatability, selectivity, and stability, this method opened up a new avenue for realizing the ultrasensitive detection of Aβ and other biomarkers in a real sample analysis.